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xfs_log.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_log_priv.h"
#include "xfs_buf_item.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_log_recover.h"
#include "xfs_trans_priv.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_rw.h"

kmem_zone_t *xfs_log_ticket_zone;

#define xlog_write_adv_cnt(ptr, len, off, bytes) \
      { (ptr) += (bytes); \
        (len) -= (bytes); \
        (off) += (bytes);}

/* Local miscellaneous function prototypes */
STATIC int   xlog_bdstrat_cb(struct xfs_buf *);
STATIC int   xlog_commit_record(xfs_mount_t *mp, xlog_ticket_t *ticket,
                            xlog_in_core_t **, xfs_lsn_t *);
STATIC xlog_t *  xlog_alloc_log(xfs_mount_t     *mp,
                        xfs_buftarg_t     *log_target,
                        xfs_daddr_t blk_offset,
                        int         num_bblks);
STATIC int   xlog_space_left(xlog_t *log, int cycle, int bytes);
STATIC int   xlog_sync(xlog_t *log, xlog_in_core_t *iclog);
STATIC void  xlog_dealloc_log(xlog_t *log);
STATIC int   xlog_write(xfs_mount_t *mp, xfs_log_iovec_t region[],
                      int nentries, xfs_log_ticket_t tic,
                      xfs_lsn_t *start_lsn,
                      xlog_in_core_t **commit_iclog,
                      uint flags);

/* local state machine functions */
STATIC void xlog_state_done_syncing(xlog_in_core_t *iclog, int);
STATIC void xlog_state_do_callback(xlog_t *log,int aborted, xlog_in_core_t *iclog);
STATIC int  xlog_state_get_iclog_space(xlog_t         *log,
                               int        len,
                               xlog_in_core_t   **iclog,
                               xlog_ticket_t    *ticket,
                               int        *continued_write,
                               int        *logoffsetp);
STATIC int  xlog_state_release_iclog(xlog_t           *log,
                             xlog_in_core_t     *iclog);
STATIC void xlog_state_switch_iclogs(xlog_t           *log,
                             xlog_in_core_t *iclog,
                             int          eventual_size);
STATIC int  xlog_state_sync(xlog_t              *log,
                      xfs_lsn_t                 lsn,
                      uint                flags,
                      int                       *log_flushed);
STATIC int  xlog_state_sync_all(xlog_t *log, uint flags, int *log_flushed);
STATIC void xlog_state_want_sync(xlog_t   *log, xlog_in_core_t *iclog);

/* local functions to manipulate grant head */
STATIC int  xlog_grant_log_space(xlog_t         *log,
                         xlog_ticket_t    *xtic);
STATIC void xlog_grant_push_ail(xfs_mount_t     *mp,
                        int         need_bytes);
STATIC void xlog_regrant_reserve_log_space(xlog_t      *log,
                                 xlog_ticket_t *ticket);
STATIC int xlog_regrant_write_log_space(xlog_t        *log,
                               xlog_ticket_t  *ticket);
STATIC void xlog_ungrant_log_space(xlog_t  *log,
                           xlog_ticket_t *ticket);


/* local ticket functions */
STATIC xlog_ticket_t    *xlog_ticket_alloc(xlog_t *log,
                               int  unit_bytes,
                               int  count,
                               char clientid,
                               uint flags);

#if defined(DEBUG)
STATIC void xlog_verify_dest_ptr(xlog_t *log, __psint_t ptr);
STATIC void xlog_verify_grant_head(xlog_t *log, int equals);
STATIC void xlog_verify_iclog(xlog_t *log, xlog_in_core_t *iclog,
                          int count, boolean_t syncing);
STATIC void xlog_verify_tail_lsn(xlog_t *log, xlog_in_core_t *iclog,
                             xfs_lsn_t tail_lsn);
#else
#define xlog_verify_dest_ptr(a,b)
#define xlog_verify_grant_head(a,b)
#define xlog_verify_iclog(a,b,c,d)
#define xlog_verify_tail_lsn(a,b,c)
#endif

STATIC int  xlog_iclogs_empty(xlog_t *log);

#if defined(XFS_LOG_TRACE)

#define XLOG_TRACE_LOGGRANT_SIZE    2048
#define XLOG_TRACE_ICLOG_SIZE       256

void
xlog_trace_loggrant_alloc(xlog_t *log)
{
      log->l_grant_trace = ktrace_alloc(XLOG_TRACE_LOGGRANT_SIZE, KM_NOFS);
}

void
xlog_trace_loggrant_dealloc(xlog_t *log)
{
      ktrace_free(log->l_grant_trace);
}

void
xlog_trace_loggrant(xlog_t *log, xlog_ticket_t *tic, xfs_caddr_t string)
{
      unsigned long cnts;

      /* ticket counts are 1 byte each */
      cnts = ((unsigned long)tic->t_ocnt) | ((unsigned long)tic->t_cnt) << 8;

      ktrace_enter(log->l_grant_trace,
                 (void *)tic,
                 (void *)log->l_reserve_headq,
                 (void *)log->l_write_headq,
                 (void *)((unsigned long)log->l_grant_reserve_cycle),
                 (void *)((unsigned long)log->l_grant_reserve_bytes),
                 (void *)((unsigned long)log->l_grant_write_cycle),
                 (void *)((unsigned long)log->l_grant_write_bytes),
                 (void *)((unsigned long)log->l_curr_cycle),
                 (void *)((unsigned long)log->l_curr_block),
                 (void *)((unsigned long)CYCLE_LSN(log->l_tail_lsn)),
                 (void *)((unsigned long)BLOCK_LSN(log->l_tail_lsn)),
                 (void *)string,
                 (void *)((unsigned long)tic->t_trans_type),
                 (void *)cnts,
                 (void *)((unsigned long)tic->t_curr_res),
                 (void *)((unsigned long)tic->t_unit_res));
}

void
xlog_trace_iclog_alloc(xlog_in_core_t *iclog)
{
      iclog->ic_trace = ktrace_alloc(XLOG_TRACE_ICLOG_SIZE, KM_NOFS);
}

void
xlog_trace_iclog_dealloc(xlog_in_core_t *iclog)
{
      ktrace_free(iclog->ic_trace);
}

void
xlog_trace_iclog(xlog_in_core_t *iclog, uint state)
{
      ktrace_enter(iclog->ic_trace,
                 (void *)((unsigned long)state),
                 (void *)((unsigned long)current_pid()),
                 (void *)NULL, (void *)NULL, (void *)NULL, (void *)NULL,
                 (void *)NULL, (void *)NULL, (void *)NULL, (void *)NULL,
                 (void *)NULL, (void *)NULL, (void *)NULL, (void *)NULL,
                 (void *)NULL, (void *)NULL);
}
#else

#define     xlog_trace_loggrant_alloc(log)
#define     xlog_trace_loggrant_dealloc(log)
#define     xlog_trace_loggrant(log,tic,string)

#define     xlog_trace_iclog_alloc(iclog)
#define     xlog_trace_iclog_dealloc(iclog)
#define     xlog_trace_iclog(iclog,state)

#endif /* XFS_LOG_TRACE */


static void
xlog_ins_ticketq(struct xlog_ticket **qp, struct xlog_ticket *tic)
{
      if (*qp) {
            tic->t_next     = (*qp);
            tic->t_prev     = (*qp)->t_prev;
            (*qp)->t_prev->t_next = tic;
            (*qp)->t_prev         = tic;
      } else {
            tic->t_prev = tic->t_next = tic;
            *qp = tic;
      }

      tic->t_flags |= XLOG_TIC_IN_Q;
}

static void
xlog_del_ticketq(struct xlog_ticket **qp, struct xlog_ticket *tic)
{
      if (tic == tic->t_next) {
            *qp = NULL;
      } else {
            *qp = tic->t_next;
            tic->t_next->t_prev = tic->t_prev;
            tic->t_prev->t_next = tic->t_next;
      }

      tic->t_next = tic->t_prev = NULL;
      tic->t_flags &= ~XLOG_TIC_IN_Q;
}

static void
xlog_grant_sub_space(struct log *log, int bytes)
{
      log->l_grant_write_bytes -= bytes;
      if (log->l_grant_write_bytes < 0) {
            log->l_grant_write_bytes += log->l_logsize;
            log->l_grant_write_cycle--;
      }

      log->l_grant_reserve_bytes -= bytes;
      if ((log)->l_grant_reserve_bytes < 0) {
            log->l_grant_reserve_bytes += log->l_logsize;
            log->l_grant_reserve_cycle--;
      }

}

static void
xlog_grant_add_space_write(struct log *log, int bytes)
{
      int tmp = log->l_logsize - log->l_grant_write_bytes;
      if (tmp > bytes)
            log->l_grant_write_bytes += bytes;
      else {
            log->l_grant_write_cycle++;
            log->l_grant_write_bytes = bytes - tmp;
      }
}

static void
xlog_grant_add_space_reserve(struct log *log, int bytes)
{
      int tmp = log->l_logsize - log->l_grant_reserve_bytes;
      if (tmp > bytes)
            log->l_grant_reserve_bytes += bytes;
      else {
            log->l_grant_reserve_cycle++;
            log->l_grant_reserve_bytes = bytes - tmp;
      }
}

static inline void
xlog_grant_add_space(struct log *log, int bytes)
{
      xlog_grant_add_space_write(log, bytes);
      xlog_grant_add_space_reserve(log, bytes);
}

static void
xlog_tic_reset_res(xlog_ticket_t *tic)
{
      tic->t_res_num = 0;
      tic->t_res_arr_sum = 0;
      tic->t_res_num_ophdrs = 0;
}

static void
xlog_tic_add_region(xlog_ticket_t *tic, uint len, uint type)
{
      if (tic->t_res_num == XLOG_TIC_LEN_MAX) {
            /* add to overflow and start again */
            tic->t_res_o_flow += tic->t_res_arr_sum;
            tic->t_res_num = 0;
            tic->t_res_arr_sum = 0;
      }

      tic->t_res_arr[tic->t_res_num].r_len = len;
      tic->t_res_arr[tic->t_res_num].r_type = type;
      tic->t_res_arr_sum += len;
      tic->t_res_num++;
}

/*
 * NOTES:
 *
 *    1. currblock field gets updated at startup and after in-core logs
 *          marked as with WANT_SYNC.
 */

/*
 * This routine is called when a user of a log manager ticket is done with
 * the reservation.  If the ticket was ever used, then a commit record for
 * the associated transaction is written out as a log operation header with
 * no data.  The flag XLOG_TIC_INITED is set when the first write occurs with
 * a given ticket.  If the ticket was one with a permanent reservation, then
 * a few operations are done differently.  Permanent reservation tickets by
 * default don't release the reservation.  They just commit the current
 * transaction with the belief that the reservation is still needed.  A flag
 * must be passed in before permanent reservations are actually released.
 * When these type of tickets are not released, they need to be set into
 * the inited state again.  By doing this, a start record will be written
 * out when the next write occurs.
 */
xfs_lsn_t
xfs_log_done(xfs_mount_t      *mp,
           xfs_log_ticket_t   xtic,
           void         **iclog,
           uint         flags)
{
      xlog_t            *log    = mp->m_log;
      xlog_ticket_t     *ticket = (xfs_log_ticket_t) xtic;
      xfs_lsn_t   lsn   = 0;

      if (XLOG_FORCED_SHUTDOWN(log) ||
          /*
           * If nothing was ever written, don't write out commit record.
           * If we get an error, just continue and give back the log ticket.
           */
          (((ticket->t_flags & XLOG_TIC_INITED) == 0) &&
           (xlog_commit_record(mp, ticket,
                         (xlog_in_core_t **)iclog, &lsn)))) {
            lsn = (xfs_lsn_t) -1;
            if (ticket->t_flags & XLOG_TIC_PERM_RESERV) {
                  flags |= XFS_LOG_REL_PERM_RESERV;
            }
      }


      if ((ticket->t_flags & XLOG_TIC_PERM_RESERV) == 0 ||
          (flags & XFS_LOG_REL_PERM_RESERV)) {
            /*
             * Release ticket if not permanent reservation or a specific
             * request has been made to release a permanent reservation.
             */
            xlog_trace_loggrant(log, ticket, "xfs_log_done: (non-permanent)");
            xlog_ungrant_log_space(log, ticket);
            xfs_log_ticket_put(ticket);
      } else {
            xlog_trace_loggrant(log, ticket, "xfs_log_done: (permanent)");
            xlog_regrant_reserve_log_space(log, ticket);
            /* If this ticket was a permanent reservation and we aren't
             * trying to release it, reset the inited flags; so next time
             * we write, a start record will be written out.
             */
            ticket->t_flags |= XLOG_TIC_INITED;
      }

      return lsn;
}     /* xfs_log_done */


/*
 * Force the in-core log to disk.  If flags == XFS_LOG_SYNC,
 *    the force is done synchronously.
 *
 * Asynchronous forces are implemented by setting the WANT_SYNC
 * bit in the appropriate in-core log and then returning.
 *
 * Synchronous forces are implemented with a signal variable. All callers
 * to force a given lsn to disk will wait on a the sv attached to the
 * specific in-core log.  When given in-core log finally completes its
 * write to disk, that thread will wake up all threads waiting on the
 * sv.
 */
int
_xfs_log_force(
      xfs_mount_t *mp,
      xfs_lsn_t   lsn,
      uint        flags,
      int         *log_flushed)
{
      xlog_t            *log = mp->m_log;
      int         dummy;

      if (!log_flushed)
            log_flushed = &dummy;

      ASSERT(flags & XFS_LOG_FORCE);

      XFS_STATS_INC(xs_log_force);

      if (log->l_flags & XLOG_IO_ERROR)
            return XFS_ERROR(EIO);
      if (lsn == 0)
            return xlog_state_sync_all(log, flags, log_flushed);
      else
            return xlog_state_sync(log, lsn, flags, log_flushed);
}     /* _xfs_log_force */

/*
 * Wrapper for _xfs_log_force(), to be used when caller doesn't care
 * about errors or whether the log was flushed or not. This is the normal
 * interface to use when trying to unpin items or move the log forward.
 */
void
xfs_log_force(
      xfs_mount_t *mp,
      xfs_lsn_t   lsn,
      uint        flags)
{
      int   error;
      error = _xfs_log_force(mp, lsn, flags, NULL);
      if (error) {
            xfs_fs_cmn_err(CE_WARN, mp, "xfs_log_force: "
                  "error %d returned.", error);
      }
}


/*
 * Attaches a new iclog I/O completion callback routine during
 * transaction commit.  If the log is in error state, a non-zero
 * return code is handed back and the caller is responsible for
 * executing the callback at an appropriate time.
 */
int
xfs_log_notify(xfs_mount_t      *mp,            /* mount of partition */
             void         *iclog_hndl,    /* iclog to hang callback off */
             xfs_log_callback_t *cb)
{
      xlog_in_core_t      *iclog = (xlog_in_core_t *)iclog_hndl;
      int   abortflg;

      spin_lock(&iclog->ic_callback_lock);
      abortflg = (iclog->ic_state & XLOG_STATE_IOERROR);
      if (!abortflg) {
            ASSERT_ALWAYS((iclog->ic_state == XLOG_STATE_ACTIVE) ||
                        (iclog->ic_state == XLOG_STATE_WANT_SYNC));
            cb->cb_next = NULL;
            *(iclog->ic_callback_tail) = cb;
            iclog->ic_callback_tail = &(cb->cb_next);
      }
      spin_unlock(&iclog->ic_callback_lock);
      return abortflg;
}     /* xfs_log_notify */

int
xfs_log_release_iclog(xfs_mount_t *mp,
                  void    *iclog_hndl)
{
      xlog_t *log = mp->m_log;
      xlog_in_core_t      *iclog = (xlog_in_core_t *)iclog_hndl;

      if (xlog_state_release_iclog(log, iclog)) {
            xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
            return EIO;
      }

      return 0;
}

/*
 *  1. Reserve an amount of on-disk log space and return a ticket corresponding
 *    to the reservation.
 *  2. Potentially, push buffers at tail of log to disk.
 *
 * Each reservation is going to reserve extra space for a log record header.
 * When writes happen to the on-disk log, we don't subtract the length of the
 * log record header from any reservation.  By wasting space in each
 * reservation, we prevent over allocation problems.
 */
int
xfs_log_reserve(xfs_mount_t    *mp,
            int          unit_bytes,
            int          cnt,
            xfs_log_ticket_t *ticket,
            __uint8_t    client,
            uint         flags,
            uint         t_type)
{
      xlog_t            *log = mp->m_log;
      xlog_ticket_t     *internal_ticket;
      int         retval = 0;

      ASSERT(client == XFS_TRANSACTION || client == XFS_LOG);
      ASSERT((flags & XFS_LOG_NOSLEEP) == 0);

      if (XLOG_FORCED_SHUTDOWN(log))
            return XFS_ERROR(EIO);

      XFS_STATS_INC(xs_try_logspace);

      if (*ticket != NULL) {
            ASSERT(flags & XFS_LOG_PERM_RESERV);
            internal_ticket = (xlog_ticket_t *)*ticket;
            xlog_trace_loggrant(log, internal_ticket, "xfs_log_reserve: existing ticket (permanent trans)");
            xlog_grant_push_ail(mp, internal_ticket->t_unit_res);
            retval = xlog_regrant_write_log_space(log, internal_ticket);
      } else {
            /* may sleep if need to allocate more tickets */
            internal_ticket = xlog_ticket_alloc(log, unit_bytes, cnt,
                                      client, flags);
            if (!internal_ticket)
                  return XFS_ERROR(ENOMEM);
            internal_ticket->t_trans_type = t_type;
            *ticket = internal_ticket;
            xlog_trace_loggrant(log, internal_ticket, 
                  (internal_ticket->t_flags & XLOG_TIC_PERM_RESERV) ?
                  "xfs_log_reserve: create new ticket (permanent trans)" :
                  "xfs_log_reserve: create new ticket");
            xlog_grant_push_ail(mp,
                            (internal_ticket->t_unit_res *
                             internal_ticket->t_cnt));
            retval = xlog_grant_log_space(log, internal_ticket);
      }

      return retval;
}     /* xfs_log_reserve */


/*
 * Mount a log filesystem
 *
 * mp       - ubiquitous xfs mount point structure
 * log_target     - buftarg of on-disk log device
 * blk_offset     - Start block # where block size is 512 bytes (BBSIZE)
 * num_bblocks    - Number of BBSIZE blocks in on-disk log
 *
 * Return error or zero.
 */
int
xfs_log_mount(
      xfs_mount_t *mp,
      xfs_buftarg_t     *log_target,
      xfs_daddr_t blk_offset,
      int         num_bblks)
{
      int         error;

      if (!(mp->m_flags & XFS_MOUNT_NORECOVERY))
            cmn_err(CE_NOTE, "XFS mounting filesystem %s", mp->m_fsname);
      else {
            cmn_err(CE_NOTE,
                  "!Mounting filesystem \"%s\" in no-recovery mode.  Filesystem will be inconsistent.",
                  mp->m_fsname);
            ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
      }

      mp->m_log = xlog_alloc_log(mp, log_target, blk_offset, num_bblks);
      if (IS_ERR(mp->m_log)) {
            error = -PTR_ERR(mp->m_log);
            goto out;
      }

      /*
       * Initialize the AIL now we have a log.
       */
      error = xfs_trans_ail_init(mp);
      if (error) {
            cmn_err(CE_WARN, "XFS: AIL initialisation failed: error %d", error);
            goto out_free_log;
      }
      mp->m_log->l_ailp = mp->m_ail;

      /*
       * skip log recovery on a norecovery mount.  pretend it all
       * just worked.
       */
      if (!(mp->m_flags & XFS_MOUNT_NORECOVERY)) {
            int   readonly = (mp->m_flags & XFS_MOUNT_RDONLY);

            if (readonly)
                  mp->m_flags &= ~XFS_MOUNT_RDONLY;

            error = xlog_recover(mp->m_log);

            if (readonly)
                  mp->m_flags |= XFS_MOUNT_RDONLY;
            if (error) {
                  cmn_err(CE_WARN, "XFS: log mount/recovery failed: error %d", error);
                  goto out_destroy_ail;
            }
      }

      /* Normal transactions can now occur */
      mp->m_log->l_flags &= ~XLOG_ACTIVE_RECOVERY;

      return 0;

out_destroy_ail:
      xfs_trans_ail_destroy(mp);
out_free_log:
      xlog_dealloc_log(mp->m_log);
out:
      return error;
}

/*
 * Finish the recovery of the file system.  This is separate from
 * the xfs_log_mount() call, because it depends on the code in
 * xfs_mountfs() to read in the root and real-time bitmap inodes
 * between calling xfs_log_mount() and here.
 *
 * mp       - ubiquitous xfs mount point structure
 */
int
xfs_log_mount_finish(xfs_mount_t *mp)
{
      int   error;

      if (!(mp->m_flags & XFS_MOUNT_NORECOVERY))
            error = xlog_recover_finish(mp->m_log);
      else {
            error = 0;
            ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
      }

      return error;
}

/*
 * Final log writes as part of unmount.
 *
 * Mark the filesystem clean as unmount happens.  Note that during relocation
 * this routine needs to be executed as part of source-bag while the
 * deallocation must not be done until source-end.
 */

/*
 * Unmount record used to have a string "Unmount filesystem--" in the
 * data section where the "Un" was really a magic number (XLOG_UNMOUNT_TYPE).
 * We just write the magic number now since that particular field isn't
 * currently architecture converted and "nUmount" is a bit foo.
 * As far as I know, there weren't any dependencies on the old behaviour.
 */

int
xfs_log_unmount_write(xfs_mount_t *mp)
{
      xlog_t             *log = mp->m_log;
      xlog_in_core_t     *iclog;
#ifdef DEBUG
      xlog_in_core_t     *first_iclog;
#endif
      xfs_log_iovec_t  reg[1];
      xfs_log_ticket_t tic = NULL;
      xfs_lsn_t    lsn;
      int          error;

      /* the data section must be 32 bit size aligned */
      struct {
          __uint16_t magic;
          __uint16_t pad1;
          __uint32_t pad2; /* may as well make it 64 bits */
      } magic = { XLOG_UNMOUNT_TYPE, 0, 0 };

      /*
       * Don't write out unmount record on read-only mounts.
       * Or, if we are doing a forced umount (typically because of IO errors).
       */
      if (mp->m_flags & XFS_MOUNT_RDONLY)
            return 0;

      error = _xfs_log_force(mp, 0, XFS_LOG_FORCE|XFS_LOG_SYNC, NULL);
      ASSERT(error || !(XLOG_FORCED_SHUTDOWN(log)));

#ifdef DEBUG
      first_iclog = iclog = log->l_iclog;
      do {
            if (!(iclog->ic_state & XLOG_STATE_IOERROR)) {
                  ASSERT(iclog->ic_state & XLOG_STATE_ACTIVE);
                  ASSERT(iclog->ic_offset == 0);
            }
            iclog = iclog->ic_next;
      } while (iclog != first_iclog);
#endif
      if (! (XLOG_FORCED_SHUTDOWN(log))) {
            reg[0].i_addr = (void*)&magic;
            reg[0].i_len  = sizeof(magic);
            XLOG_VEC_SET_TYPE(&reg[0], XLOG_REG_TYPE_UNMOUNT);

            error = xfs_log_reserve(mp, 600, 1, &tic,
                              XFS_LOG, 0, XLOG_UNMOUNT_REC_TYPE);
            if (!error) {
                  /* remove inited flag */
                  ((xlog_ticket_t *)tic)->t_flags = 0;
                  error = xlog_write(mp, reg, 1, tic, &lsn,
                                 NULL, XLOG_UNMOUNT_TRANS);
                  /*
                   * At this point, we're umounting anyway,
                   * so there's no point in transitioning log state
                   * to IOERROR. Just continue...
                   */
            }

            if (error) {
                  xfs_fs_cmn_err(CE_ALERT, mp,
                        "xfs_log_unmount: unmount record failed");
            }


            spin_lock(&log->l_icloglock);
            iclog = log->l_iclog;
            atomic_inc(&iclog->ic_refcnt);
            xlog_state_want_sync(log, iclog);
            spin_unlock(&log->l_icloglock);
            error = xlog_state_release_iclog(log, iclog);

            spin_lock(&log->l_icloglock);
            if (!(iclog->ic_state == XLOG_STATE_ACTIVE ||
                  iclog->ic_state == XLOG_STATE_DIRTY)) {
                  if (!XLOG_FORCED_SHUTDOWN(log)) {
                        sv_wait(&iclog->ic_force_wait, PMEM,
                              &log->l_icloglock, s);
                  } else {
                        spin_unlock(&log->l_icloglock);
                  }
            } else {
                  spin_unlock(&log->l_icloglock);
            }
            if (tic) {
                  xlog_trace_loggrant(log, tic, "unmount rec");
                  xlog_ungrant_log_space(log, tic);
                  xfs_log_ticket_put(tic);
            }
      } else {
            /*
             * We're already in forced_shutdown mode, couldn't
             * even attempt to write out the unmount transaction.
             *
             * Go through the motions of sync'ing and releasing
             * the iclog, even though no I/O will actually happen,
             * we need to wait for other log I/Os that may already
             * be in progress.  Do this as a separate section of
             * code so we'll know if we ever get stuck here that
             * we're in this odd situation of trying to unmount
             * a file system that went into forced_shutdown as
             * the result of an unmount..
             */
            spin_lock(&log->l_icloglock);
            iclog = log->l_iclog;
            atomic_inc(&iclog->ic_refcnt);

            xlog_state_want_sync(log, iclog);
            spin_unlock(&log->l_icloglock);
            error =  xlog_state_release_iclog(log, iclog);

            spin_lock(&log->l_icloglock);

            if ( ! (   iclog->ic_state == XLOG_STATE_ACTIVE
                  || iclog->ic_state == XLOG_STATE_DIRTY
                  || iclog->ic_state == XLOG_STATE_IOERROR) ) {

                        sv_wait(&iclog->ic_force_wait, PMEM,
                              &log->l_icloglock, s);
            } else {
                  spin_unlock(&log->l_icloglock);
            }
      }

      return error;
}     /* xfs_log_unmount_write */

/*
 * Deallocate log structures for unmount/relocation.
 *
 * We need to stop the aild from running before we destroy
 * and deallocate the log as the aild references the log.
 */
void
xfs_log_unmount(xfs_mount_t *mp)
{
      xfs_trans_ail_destroy(mp);
      xlog_dealloc_log(mp->m_log);
}

/*
 * Write region vectors to log.  The write happens using the space reservation
 * of the ticket (tic).  It is not a requirement that all writes for a given
 * transaction occur with one call to xfs_log_write().
 */
int
xfs_log_write(xfs_mount_t *   mp,
            xfs_log_iovec_t   reg[],
            int         nentries,
            xfs_log_ticket_t  tic,
            xfs_lsn_t         *start_lsn)
{
      int   error;
      xlog_t *log = mp->m_log;

      if (XLOG_FORCED_SHUTDOWN(log))
            return XFS_ERROR(EIO);

      if ((error = xlog_write(mp, reg, nentries, tic, start_lsn, NULL, 0))) {
            xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
      }
      return error;
}     /* xfs_log_write */


void
xfs_log_move_tail(xfs_mount_t *mp,
              xfs_lsn_t tail_lsn)
{
      xlog_ticket_t     *tic;
      xlog_t            *log = mp->m_log;
      int         need_bytes, free_bytes, cycle, bytes;

      if (XLOG_FORCED_SHUTDOWN(log))
            return;

      if (tail_lsn == 0) {
            /* needed since sync_lsn is 64 bits */
            spin_lock(&log->l_icloglock);
            tail_lsn = log->l_last_sync_lsn;
            spin_unlock(&log->l_icloglock);
      }

      spin_lock(&log->l_grant_lock);

      /* Also an invalid lsn.  1 implies that we aren't passing in a valid
       * tail_lsn.
       */
      if (tail_lsn != 1) {
            log->l_tail_lsn = tail_lsn;
      }

      if ((tic = log->l_write_headq)) {
#ifdef DEBUG
            if (log->l_flags & XLOG_ACTIVE_RECOVERY)
                  panic("Recovery problem");
#endif
            cycle = log->l_grant_write_cycle;
            bytes = log->l_grant_write_bytes;
            free_bytes = xlog_space_left(log, cycle, bytes);
            do {
                  ASSERT(tic->t_flags & XLOG_TIC_PERM_RESERV);

                  if (free_bytes < tic->t_unit_res && tail_lsn != 1)
                        break;
                  tail_lsn = 0;
                  free_bytes -= tic->t_unit_res;
                  sv_signal(&tic->t_wait);
                  tic = tic->t_next;
            } while (tic != log->l_write_headq);
      }
      if ((tic = log->l_reserve_headq)) {
#ifdef DEBUG
            if (log->l_flags & XLOG_ACTIVE_RECOVERY)
                  panic("Recovery problem");
#endif
            cycle = log->l_grant_reserve_cycle;
            bytes = log->l_grant_reserve_bytes;
            free_bytes = xlog_space_left(log, cycle, bytes);
            do {
                  if (tic->t_flags & XLOG_TIC_PERM_RESERV)
                        need_bytes = tic->t_unit_res*tic->t_cnt;
                  else
                        need_bytes = tic->t_unit_res;
                  if (free_bytes < need_bytes && tail_lsn != 1)
                        break;
                  tail_lsn = 0;
                  free_bytes -= need_bytes;
                  sv_signal(&tic->t_wait);
                  tic = tic->t_next;
            } while (tic != log->l_reserve_headq);
      }
      spin_unlock(&log->l_grant_lock);
}     /* xfs_log_move_tail */

/*
 * Determine if we have a transaction that has gone to disk
 * that needs to be covered. Log activity needs to be idle (no AIL and
 * nothing in the iclogs). And, we need to be in the right state indicating
 * something has gone out.
 */
int
xfs_log_need_covered(xfs_mount_t *mp)
{
      int         needed = 0;
      xlog_t            *log = mp->m_log;

      if (!xfs_fs_writable(mp))
            return 0;

      spin_lock(&log->l_icloglock);
      if (((log->l_covered_state == XLOG_STATE_COVER_NEED) ||
            (log->l_covered_state == XLOG_STATE_COVER_NEED2))
                  && !xfs_trans_ail_tail(log->l_ailp)
                  && xlog_iclogs_empty(log)) {
            if (log->l_covered_state == XLOG_STATE_COVER_NEED)
                  log->l_covered_state = XLOG_STATE_COVER_DONE;
            else {
                  ASSERT(log->l_covered_state == XLOG_STATE_COVER_NEED2);
                  log->l_covered_state = XLOG_STATE_COVER_DONE2;
            }
            needed = 1;
      }
      spin_unlock(&log->l_icloglock);
      return needed;
}

/******************************************************************************
 *
 *    local routines
 *
 ******************************************************************************
 */

/* xfs_trans_tail_ail returns 0 when there is nothing in the list.
 * The log manager must keep track of the last LR which was committed
 * to disk.  The lsn of this LR will become the new tail_lsn whenever
 * xfs_trans_tail_ail returns 0.  If we don't do this, we run into
 * the situation where stuff could be written into the log but nothing
 * was ever in the AIL when asked.  Eventually, we panic since the
 * tail hits the head.
 *
 * We may be holding the log iclog lock upon entering this routine.
 */
xfs_lsn_t
xlog_assign_tail_lsn(xfs_mount_t *mp)
{
      xfs_lsn_t tail_lsn;
      xlog_t        *log = mp->m_log;

      tail_lsn = xfs_trans_ail_tail(mp->m_ail);
      spin_lock(&log->l_grant_lock);
      if (tail_lsn != 0) {
            log->l_tail_lsn = tail_lsn;
      } else {
            tail_lsn = log->l_tail_lsn = log->l_last_sync_lsn;
      }
      spin_unlock(&log->l_grant_lock);

      return tail_lsn;
}     /* xlog_assign_tail_lsn */


/*
 * Return the space in the log between the tail and the head.  The head
 * is passed in the cycle/bytes formal parms.  In the special case where
 * the reserve head has wrapped passed the tail, this calculation is no
 * longer valid.  In this case, just return 0 which means there is no space
 * in the log.  This works for all places where this function is called
 * with the reserve head.  Of course, if the write head were to ever
 * wrap the tail, we should blow up.  Rather than catch this case here,
 * we depend on other ASSERTions in other parts of the code.   XXXmiken
 *
 * This code also handles the case where the reservation head is behind
 * the tail.  The details of this case are described below, but the end
 * result is that we return the size of the log as the amount of space left.
 */
STATIC int
xlog_space_left(xlog_t *log, int cycle, int bytes)
{
      int free_bytes;
      int tail_bytes;
      int tail_cycle;

      tail_bytes = BBTOB(BLOCK_LSN(log->l_tail_lsn));
      tail_cycle = CYCLE_LSN(log->l_tail_lsn);
      if ((tail_cycle == cycle) && (bytes >= tail_bytes)) {
            free_bytes = log->l_logsize - (bytes - tail_bytes);
      } else if ((tail_cycle + 1) < cycle) {
            return 0;
      } else if (tail_cycle < cycle) {
            ASSERT(tail_cycle == (cycle - 1));
            free_bytes = tail_bytes - bytes;
      } else {
            /*
             * The reservation head is behind the tail.
             * In this case we just want to return the size of the
             * log as the amount of space left.
             */
            xfs_fs_cmn_err(CE_ALERT, log->l_mp,
                  "xlog_space_left: head behind tail\n"
                  "  tail_cycle = %d, tail_bytes = %d\n"
                  "  GH   cycle = %d, GH   bytes = %d",
                  tail_cycle, tail_bytes, cycle, bytes);
            ASSERT(0);
            free_bytes = log->l_logsize;
      }
      return free_bytes;
}     /* xlog_space_left */


/*
 * Log function which is called when an io completes.
 *
 * The log manager needs its own routine, in order to control what
 * happens with the buffer after the write completes.
 */
void
xlog_iodone(xfs_buf_t *bp)
{
      xlog_in_core_t    *iclog;
      xlog_t            *l;
      int         aborted;

      iclog = XFS_BUF_FSPRIVATE(bp, xlog_in_core_t *);
      ASSERT(XFS_BUF_FSPRIVATE2(bp, unsigned long) == (unsigned long) 2);
      XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)1);
      aborted = 0;
      l = iclog->ic_log;

      /*
       * If the _XFS_BARRIER_FAILED flag was set by a lower
       * layer, it means the underlying device no longer supports
       * barrier I/O. Warn loudly and turn off barriers.
       */
      if (bp->b_flags & _XFS_BARRIER_FAILED) {
            bp->b_flags &= ~_XFS_BARRIER_FAILED;
            l->l_mp->m_flags &= ~XFS_MOUNT_BARRIER;
            xfs_fs_cmn_err(CE_WARN, l->l_mp,
                        "xlog_iodone: Barriers are no longer supported"
                        " by device. Disabling barriers\n");
            xfs_buftrace("XLOG_IODONE BARRIERS OFF", bp);
      }

      /*
       * Race to shutdown the filesystem if we see an error.
       */
      if (XFS_TEST_ERROR((XFS_BUF_GETERROR(bp)), l->l_mp,
                  XFS_ERRTAG_IODONE_IOERR, XFS_RANDOM_IODONE_IOERR)) {
            xfs_ioerror_alert("xlog_iodone", l->l_mp, bp, XFS_BUF_ADDR(bp));
            XFS_BUF_STALE(bp);
            xfs_force_shutdown(l->l_mp, SHUTDOWN_LOG_IO_ERROR);
            /*
             * This flag will be propagated to the trans-committed
             * callback routines to let them know that the log-commit
             * didn't succeed.
             */
            aborted = XFS_LI_ABORTED;
      } else if (iclog->ic_state & XLOG_STATE_IOERROR) {
            aborted = XFS_LI_ABORTED;
      }

      /* log I/O is always issued ASYNC */
      ASSERT(XFS_BUF_ISASYNC(bp));
      xlog_state_done_syncing(iclog, aborted);
      /*
       * do not reference the buffer (bp) here as we could race
       * with it being freed after writing the unmount record to the
       * log.
       */

}     /* xlog_iodone */

/*
 * The bdstrat callback function for log bufs. This gives us a central
 * place to trap bufs in case we get hit by a log I/O error and need to
 * shutdown. Actually, in practice, even when we didn't get a log error,
 * we transition the iclogs to IOERROR state *after* flushing all existing
 * iclogs to disk. This is because we don't want anymore new transactions to be
 * started or completed afterwards.
 */
STATIC int
xlog_bdstrat_cb(struct xfs_buf *bp)
{
      xlog_in_core_t *iclog;

      iclog = XFS_BUF_FSPRIVATE(bp, xlog_in_core_t *);

      if ((iclog->ic_state & XLOG_STATE_IOERROR) == 0) {
        /* note for irix bstrat will need  struct bdevsw passed
         * Fix the following macro if the code ever is merged
         */
          XFS_bdstrat(bp);
            return 0;
      }

      xfs_buftrace("XLOG__BDSTRAT IOERROR", bp);
      XFS_BUF_ERROR(bp, EIO);
      XFS_BUF_STALE(bp);
      xfs_biodone(bp);
      return XFS_ERROR(EIO);


}

/*
 * Return size of each in-core log record buffer.
 *
 * All machines get 8 x 32kB buffers by default, unless tuned otherwise.
 *
 * If the filesystem blocksize is too large, we may need to choose a
 * larger size since the directory code currently logs entire blocks.
 */

STATIC void
xlog_get_iclog_buffer_size(xfs_mount_t    *mp,
                     xlog_t   *log)
{
      int size;
      int xhdrs;

      if (mp->m_logbufs <= 0)
            log->l_iclog_bufs = XLOG_MAX_ICLOGS;
      else
            log->l_iclog_bufs = mp->m_logbufs;

      /*
       * Buffer size passed in from mount system call.
       */
      if (mp->m_logbsize > 0) {
            size = log->l_iclog_size = mp->m_logbsize;
            log->l_iclog_size_log = 0;
            while (size != 1) {
                  log->l_iclog_size_log++;
                  size >>= 1;
            }

            if (xfs_sb_version_haslogv2(&mp->m_sb)) {
                  /* # headers = size / 32k
                   * one header holds cycles from 32k of data
                   */

                  xhdrs = mp->m_logbsize / XLOG_HEADER_CYCLE_SIZE;
                  if (mp->m_logbsize % XLOG_HEADER_CYCLE_SIZE)
                        xhdrs++;
                  log->l_iclog_hsize = xhdrs << BBSHIFT;
                  log->l_iclog_heads = xhdrs;
            } else {
                  ASSERT(mp->m_logbsize <= XLOG_BIG_RECORD_BSIZE);
                  log->l_iclog_hsize = BBSIZE;
                  log->l_iclog_heads = 1;
            }
            goto done;
      }

      /* All machines use 32kB buffers by default. */
      log->l_iclog_size = XLOG_BIG_RECORD_BSIZE;
      log->l_iclog_size_log = XLOG_BIG_RECORD_BSHIFT;

      /* the default log size is 16k or 32k which is one header sector */
      log->l_iclog_hsize = BBSIZE;
      log->l_iclog_heads = 1;

done:
      /* are we being asked to make the sizes selected above visible? */
      if (mp->m_logbufs == 0)
            mp->m_logbufs = log->l_iclog_bufs;
      if (mp->m_logbsize == 0)
            mp->m_logbsize = log->l_iclog_size;
}     /* xlog_get_iclog_buffer_size */


/*
 * This routine initializes some of the log structure for a given mount point.
 * Its primary purpose is to fill in enough, so recovery can occur.  However,
 * some other stuff may be filled in too.
 */
STATIC xlog_t *
xlog_alloc_log(xfs_mount_t    *mp,
             xfs_buftarg_t    *log_target,
             xfs_daddr_t      blk_offset,
             int        num_bblks)
{
      xlog_t                  *log;
      xlog_rec_header_t *head;
      xlog_in_core_t          **iclogp;
      xlog_in_core_t          *iclog, *prev_iclog=NULL;
      xfs_buf_t         *bp;
      int               i;
      int               iclogsize;
      int               error = ENOMEM;

      log = kmem_zalloc(sizeof(xlog_t), KM_MAYFAIL);
      if (!log) {
            xlog_warn("XFS: Log allocation failed: No memory!");
            goto out;
      }

      log->l_mp      = mp;
      log->l_targ    = log_target;
      log->l_logsize     = BBTOB(num_bblks);
      log->l_logBBstart  = blk_offset;
      log->l_logBBsize   = num_bblks;
      log->l_covered_state = XLOG_STATE_COVER_IDLE;
      log->l_flags         |= XLOG_ACTIVE_RECOVERY;

      log->l_prev_block  = -1;
      log->l_tail_lsn      = xlog_assign_lsn(1, 0);
      /* log->l_tail_lsn = 0x100000000LL; cycle = 1; current block = 0 */
      log->l_last_sync_lsn = log->l_tail_lsn;
      log->l_curr_cycle  = 1;     /* 0 is bad since this is initial value */
      log->l_grant_reserve_cycle = 1;
      log->l_grant_write_cycle = 1;

      error = EFSCORRUPTED;
      if (xfs_sb_version_hassector(&mp->m_sb)) {
            log->l_sectbb_log = mp->m_sb.sb_logsectlog - BBSHIFT;
            if (log->l_sectbb_log < 0 ||
                log->l_sectbb_log > mp->m_sectbb_log) {
                  xlog_warn("XFS: Log sector size (0x%x) out of range.",
                                    log->l_sectbb_log);
                  goto out_free_log;
            }

            /* for larger sector sizes, must have v2 or external log */
            if (log->l_sectbb_log != 0 &&
                (log->l_logBBstart != 0 &&
                 !xfs_sb_version_haslogv2(&mp->m_sb))) {
                  xlog_warn("XFS: log sector size (0x%x) invalid "
                          "for configuration.", log->l_sectbb_log);
                  goto out_free_log;
            }
            if (mp->m_sb.sb_logsectlog < BBSHIFT) {
                  xlog_warn("XFS: Log sector log (0x%x) too small.",
                                    mp->m_sb.sb_logsectlog);
                  goto out_free_log;
            }
      }
      log->l_sectbb_mask = (1 << log->l_sectbb_log) - 1;

      xlog_get_iclog_buffer_size(mp, log);

      error = ENOMEM;
      bp = xfs_buf_get_empty(log->l_iclog_size, mp->m_logdev_targp);
      if (!bp)
            goto out_free_log;
      XFS_BUF_SET_IODONE_FUNC(bp, xlog_iodone);
      XFS_BUF_SET_BDSTRAT_FUNC(bp, xlog_bdstrat_cb);
      XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)1);
      ASSERT(XFS_BUF_ISBUSY(bp));
      ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);
      log->l_xbuf = bp;

      spin_lock_init(&log->l_icloglock);
      spin_lock_init(&log->l_grant_lock);
      sv_init(&log->l_flush_wait, 0, "flush_wait");

      xlog_trace_loggrant_alloc(log);
      /* log record size must be multiple of BBSIZE; see xlog_rec_header_t */
      ASSERT((XFS_BUF_SIZE(bp) & BBMASK) == 0);

      iclogp = &log->l_iclog;
      /*
       * The amount of memory to allocate for the iclog structure is
       * rather funky due to the way the structure is defined.  It is
       * done this way so that we can use different sizes for machines
       * with different amounts of memory.  See the definition of
       * xlog_in_core_t in xfs_log_priv.h for details.
       */
      iclogsize = log->l_iclog_size;
      ASSERT(log->l_iclog_size >= 4096);
      for (i=0; i < log->l_iclog_bufs; i++) {
            *iclogp = kmem_zalloc(sizeof(xlog_in_core_t), KM_MAYFAIL);
            if (!*iclogp)
                  goto out_free_iclog;

            iclog = *iclogp;
            iclog->ic_prev = prev_iclog;
            prev_iclog = iclog;

            bp = xfs_buf_get_noaddr(log->l_iclog_size, mp->m_logdev_targp);
            if (!bp)
                  goto out_free_iclog;
            if (!XFS_BUF_CPSEMA(bp))
                  ASSERT(0);
            XFS_BUF_SET_IODONE_FUNC(bp, xlog_iodone);
            XFS_BUF_SET_BDSTRAT_FUNC(bp, xlog_bdstrat_cb);
            XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)1);
            iclog->ic_bp = bp;
            iclog->ic_data = bp->b_addr;
#ifdef DEBUG
            log->l_iclog_bak[i] = (xfs_caddr_t)&(iclog->ic_header);
#endif
            head = &iclog->ic_header;
            memset(head, 0, sizeof(xlog_rec_header_t));
            head->h_magicno = cpu_to_be32(XLOG_HEADER_MAGIC_NUM);
            head->h_version = cpu_to_be32(
                  xfs_sb_version_haslogv2(&log->l_mp->m_sb) ? 2 : 1);
            head->h_size = cpu_to_be32(log->l_iclog_size);
            /* new fields */
            head->h_fmt = cpu_to_be32(XLOG_FMT);
            memcpy(&head->h_fs_uuid, &mp->m_sb.sb_uuid, sizeof(uuid_t));

            iclog->ic_size = XFS_BUF_SIZE(bp) - log->l_iclog_hsize;
            iclog->ic_state = XLOG_STATE_ACTIVE;
            iclog->ic_log = log;
            atomic_set(&iclog->ic_refcnt, 0);
            spin_lock_init(&iclog->ic_callback_lock);
            iclog->ic_callback_tail = &(iclog->ic_callback);
            iclog->ic_datap = (char *)iclog->ic_data + log->l_iclog_hsize;

            ASSERT(XFS_BUF_ISBUSY(iclog->ic_bp));
            ASSERT(XFS_BUF_VALUSEMA(iclog->ic_bp) <= 0);
            sv_init(&iclog->ic_force_wait, SV_DEFAULT, "iclog-force");
            sv_init(&iclog->ic_write_wait, SV_DEFAULT, "iclog-write");

            xlog_trace_iclog_alloc(iclog);

            iclogp = &iclog->ic_next;
      }
      *iclogp = log->l_iclog;             /* complete ring */
      log->l_iclog->ic_prev = prev_iclog; /* re-write 1st prev ptr */

      return log;

out_free_iclog:
      for (iclog = log->l_iclog; iclog; iclog = prev_iclog) {
            prev_iclog = iclog->ic_next;
            if (iclog->ic_bp) {
                  sv_destroy(&iclog->ic_force_wait);
                  sv_destroy(&iclog->ic_write_wait);
                  xfs_buf_free(iclog->ic_bp);
                  xlog_trace_iclog_dealloc(iclog);
            }
            kmem_free(iclog);
      }
      spinlock_destroy(&log->l_icloglock);
      spinlock_destroy(&log->l_grant_lock);
      xlog_trace_loggrant_dealloc(log);
      xfs_buf_free(log->l_xbuf);
out_free_log:
      kmem_free(log);
out:
      return ERR_PTR(-error);
}     /* xlog_alloc_log */


/*
 * Write out the commit record of a transaction associated with the given
 * ticket.  Return the lsn of the commit record.
 */
STATIC int
xlog_commit_record(xfs_mount_t  *mp,
               xlog_ticket_t *ticket,
               xlog_in_core_t **iclog,
               xfs_lsn_t      *commitlsnp)
{
      int         error;
      xfs_log_iovec_t   reg[1];

      reg[0].i_addr = NULL;
      reg[0].i_len = 0;
      XLOG_VEC_SET_TYPE(&reg[0], XLOG_REG_TYPE_COMMIT);

      ASSERT_ALWAYS(iclog);
      if ((error = xlog_write(mp, reg, 1, ticket, commitlsnp,
                         iclog, XLOG_COMMIT_TRANS))) {
            xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
      }
      return error;
}     /* xlog_commit_record */


/*
 * Push on the buffer cache code if we ever use more than 75% of the on-disk
 * log space.  This code pushes on the lsn which would supposedly free up
 * the 25% which we want to leave free.  We may need to adopt a policy which
 * pushes on an lsn which is further along in the log once we reach the high
 * water mark.  In this manner, we would be creating a low water mark.
 */
STATIC void
xlog_grant_push_ail(xfs_mount_t     *mp,
                int           need_bytes)
{
    xlog_t  *log = mp->m_log; /* pointer to the log */
    xfs_lsn_t     tail_lsn;         /* lsn of the log tail */
    xfs_lsn_t     threshold_lsn = 0;      /* lsn we'd like to be at */
    int           free_blocks;            /* free blocks left to write to */
    int           free_bytes;       /* free bytes left to write to */
    int           threshold_block;  /* block in lsn we'd like to be at */
    int           threshold_cycle;  /* lsn cycle we'd like to be at */
    int           free_threshold;

    ASSERT(BTOBB(need_bytes) < log->l_logBBsize);

    spin_lock(&log->l_grant_lock);
    free_bytes = xlog_space_left(log,
                         log->l_grant_reserve_cycle,
                         log->l_grant_reserve_bytes);
    tail_lsn = log->l_tail_lsn;
    free_blocks = BTOBBT(free_bytes);

    /*
     * Set the threshold for the minimum number of free blocks in the
     * log to the maximum of what the caller needs, one quarter of the
     * log, and 256 blocks.
     */
    free_threshold = BTOBB(need_bytes);
    free_threshold = MAX(free_threshold, (log->l_logBBsize >> 2));
    free_threshold = MAX(free_threshold, 256);
    if (free_blocks < free_threshold) {
      threshold_block = BLOCK_LSN(tail_lsn) + free_threshold;
      threshold_cycle = CYCLE_LSN(tail_lsn);
      if (threshold_block >= log->l_logBBsize) {
          threshold_block -= log->l_logBBsize;
          threshold_cycle += 1;
      }
      threshold_lsn = xlog_assign_lsn(threshold_cycle, threshold_block);

      /* Don't pass in an lsn greater than the lsn of the last
       * log record known to be on disk.
       */
      if (XFS_LSN_CMP(threshold_lsn, log->l_last_sync_lsn) > 0)
          threshold_lsn = log->l_last_sync_lsn;
    }
    spin_unlock(&log->l_grant_lock);

    /*
     * Get the transaction layer to kick the dirty buffers out to
     * disk asynchronously. No point in trying to do this if
     * the filesystem is shutting down.
     */
    if (threshold_lsn &&
      !XLOG_FORCED_SHUTDOWN(log))
          xfs_trans_ail_push(log->l_ailp, threshold_lsn);
}     /* xlog_grant_push_ail */


/*
 * Flush out the in-core log (iclog) to the on-disk log in an asynchronous 
 * fashion.  Previously, we should have moved the current iclog
 * ptr in the log to point to the next available iclog.  This allows further
 * write to continue while this code syncs out an iclog ready to go.
 * Before an in-core log can be written out, the data section must be scanned
 * to save away the 1st word of each BBSIZE block into the header.  We replace
 * it with the current cycle count.  Each BBSIZE block is tagged with the
 * cycle count because there in an implicit assumption that drives will
 * guarantee that entire 512 byte blocks get written at once.  In other words,
 * we can't have part of a 512 byte block written and part not written.  By
 * tagging each block, we will know which blocks are valid when recovering
 * after an unclean shutdown.
 *
 * This routine is single threaded on the iclog.  No other thread can be in
 * this routine with the same iclog.  Changing contents of iclog can there-
 * fore be done without grabbing the state machine lock.  Updating the global
 * log will require grabbing the lock though.
 *
 * The entire log manager uses a logical block numbering scheme.  Only
 * log_sync (and then only bwrite()) know about the fact that the log may
 * not start with block zero on a given device.  The log block start offset
 * is added immediately before calling bwrite().
 */

STATIC int
xlog_sync(xlog_t        *log,
        xlog_in_core_t  *iclog)
{
      xfs_caddr_t dptr;       /* pointer to byte sized element */
      xfs_buf_t   *bp;
      int         i;
      uint        count;            /* byte count of bwrite */
      uint        count_init; /* initial count before roundup */
      int         roundoff;       /* roundoff to BB or stripe */
      int         split = 0;  /* split write into two regions */
      int         error;
      int         v2 = xfs_sb_version_haslogv2(&log->l_mp->m_sb);

      XFS_STATS_INC(xs_log_writes);
      ASSERT(atomic_read(&iclog->ic_refcnt) == 0);

      /* Add for LR header */
      count_init = log->l_iclog_hsize + iclog->ic_offset;

      /* Round out the log write size */
      if (v2 && log->l_mp->m_sb.sb_logsunit > 1) {
            /* we have a v2 stripe unit to use */
            count = XLOG_LSUNITTOB(log, XLOG_BTOLSUNIT(log, count_init));
      } else {
            count = BBTOB(BTOBB(count_init));
      }
      roundoff = count - count_init;
      ASSERT(roundoff >= 0);
      ASSERT((v2 && log->l_mp->m_sb.sb_logsunit > 1 && 
                roundoff < log->l_mp->m_sb.sb_logsunit)
            || 
            (log->l_mp->m_sb.sb_logsunit <= 1 && 
             roundoff < BBTOB(1)));

      /* move grant heads by roundoff in sync */
      spin_lock(&log->l_grant_lock);
      xlog_grant_add_space(log, roundoff);
      spin_unlock(&log->l_grant_lock);

      /* put cycle number in every block */
      xlog_pack_data(log, iclog, roundoff); 

      /* real byte length */
      if (v2) {
            iclog->ic_header.h_len =
                  cpu_to_be32(iclog->ic_offset + roundoff);
      } else {
            iclog->ic_header.h_len =
                  cpu_to_be32(iclog->ic_offset);
      }

      bp = iclog->ic_bp;
      ASSERT(XFS_BUF_FSPRIVATE2(bp, unsigned long) == (unsigned long)1);
      XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)2);
      XFS_BUF_SET_ADDR(bp, BLOCK_LSN(be64_to_cpu(iclog->ic_header.h_lsn)));

      XFS_STATS_ADD(xs_log_blocks, BTOBB(count));

      /* Do we need to split this write into 2 parts? */
      if (XFS_BUF_ADDR(bp) + BTOBB(count) > log->l_logBBsize) {
            split = count - (BBTOB(log->l_logBBsize - XFS_BUF_ADDR(bp)));
            count = BBTOB(log->l_logBBsize - XFS_BUF_ADDR(bp));
            iclog->ic_bwritecnt = 2;      /* split into 2 writes */
      } else {
            iclog->ic_bwritecnt = 1;
      }
      XFS_BUF_SET_COUNT(bp, count);
      XFS_BUF_SET_FSPRIVATE(bp, iclog);   /* save for later */
      XFS_BUF_ZEROFLAGS(bp);
      XFS_BUF_BUSY(bp);
      XFS_BUF_ASYNC(bp);
      /*
       * Do an ordered write for the log block.
       * Its unnecessary to flush the first split block in the log wrap case.
       */
      if (!split && (log->l_mp->m_flags & XFS_MOUNT_BARRIER))
            XFS_BUF_ORDERED(bp);

      ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);
      ASSERT(XFS_BUF_ADDR(bp) + BTOBB(count) <= log->l_logBBsize);

      xlog_verify_iclog(log, iclog, count, B_TRUE);

      /* account for log which doesn't start at block #0 */
      XFS_BUF_SET_ADDR(bp, XFS_BUF_ADDR(bp) + log->l_logBBstart);
      /*
       * Don't call xfs_bwrite here. We do log-syncs even when the filesystem
       * is shutting down.
       */
      XFS_BUF_WRITE(bp);

      if ((error = XFS_bwrite(bp))) {
            xfs_ioerror_alert("xlog_sync", log->l_mp, bp,
                          XFS_BUF_ADDR(bp));
            return error;
      }
      if (split) {
            bp = iclog->ic_log->l_xbuf;
            ASSERT(XFS_BUF_FSPRIVATE2(bp, unsigned long) ==
                                          (unsigned long)1);
            XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)2);
            XFS_BUF_SET_ADDR(bp, 0);           /* logical 0 */
            XFS_BUF_SET_PTR(bp, (xfs_caddr_t)((__psint_t)&(iclog->ic_header)+
                                  (__psint_t)count), split);
            XFS_BUF_SET_FSPRIVATE(bp, iclog);
            XFS_BUF_ZEROFLAGS(bp);
            XFS_BUF_BUSY(bp);
            XFS_BUF_ASYNC(bp);
            if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
                  XFS_BUF_ORDERED(bp);
            dptr = XFS_BUF_PTR(bp);
            /*
             * Bump the cycle numbers at the start of each block
             * since this part of the buffer is at the start of
             * a new cycle.  Watch out for the header magic number
             * case, though.
             */
            for (i = 0; i < split; i += BBSIZE) {
                  be32_add_cpu((__be32 *)dptr, 1);
                  if (be32_to_cpu(*(__be32 *)dptr) == XLOG_HEADER_MAGIC_NUM)
                        be32_add_cpu((__be32 *)dptr, 1);
                  dptr += BBSIZE;
            }

            ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);
            ASSERT(XFS_BUF_ADDR(bp) + BTOBB(count) <= log->l_logBBsize);

            /* account for internal log which doesn't start at block #0 */
            XFS_BUF_SET_ADDR(bp, XFS_BUF_ADDR(bp) + log->l_logBBstart);
            XFS_BUF_WRITE(bp);
            if ((error = XFS_bwrite(bp))) {
                  xfs_ioerror_alert("xlog_sync (split)", log->l_mp,
                                bp, XFS_BUF_ADDR(bp));
                  return error;
            }
      }
      return 0;
}     /* xlog_sync */


/*
 * Deallocate a log structure
 */
STATIC void
xlog_dealloc_log(xlog_t *log)
{
      xlog_in_core_t    *iclog, *next_iclog;
      int         i;

      iclog = log->l_iclog;
      for (i=0; i<log->l_iclog_bufs; i++) {
            sv_destroy(&iclog->ic_force_wait);
            sv_destroy(&iclog->ic_write_wait);
            xfs_buf_free(iclog->ic_bp);
            xlog_trace_iclog_dealloc(iclog);
            next_iclog = iclog->ic_next;
            kmem_free(iclog);
            iclog = next_iclog;
      }
      spinlock_destroy(&log->l_icloglock);
      spinlock_destroy(&log->l_grant_lock);

      xfs_buf_free(log->l_xbuf);
      xlog_trace_loggrant_dealloc(log);
      log->l_mp->m_log = NULL;
      kmem_free(log);
}     /* xlog_dealloc_log */

/*
 * Update counters atomically now that memcpy is done.
 */
/* ARGSUSED */
static inline void
xlog_state_finish_copy(xlog_t       *log,
                   xlog_in_core_t   *iclog,
                   int        record_cnt,
                   int        copy_bytes)
{
      spin_lock(&log->l_icloglock);

      be32_add_cpu(&iclog->ic_header.h_num_logops, record_cnt);
      iclog->ic_offset += copy_bytes;

      spin_unlock(&log->l_icloglock);
}     /* xlog_state_finish_copy */




/*
 * print out info relating to regions written which consume
 * the reservation
 */
STATIC void
xlog_print_tic_res(xfs_mount_t *mp, xlog_ticket_t *ticket)
{
      uint i;
      uint ophdr_spc = ticket->t_res_num_ophdrs * (uint)sizeof(xlog_op_header_t);

      /* match with XLOG_REG_TYPE_* in xfs_log.h */
      static char *res_type_str[XLOG_REG_TYPE_MAX] = {
          "bformat",
          "bchunk",
          "efi_format",
          "efd_format",
          "iformat",
          "icore",
          "iext",
          "ibroot",
          "ilocal",
          "iattr_ext",
          "iattr_broot",
          "iattr_local",
          "qformat",
          "dquot",
          "quotaoff",
          "LR header",
          "unmount",
          "commit",
          "trans header"
      };
      static char *trans_type_str[XFS_TRANS_TYPE_MAX] = {
          "SETATTR_NOT_SIZE",
          "SETATTR_SIZE",
          "INACTIVE",
          "CREATE",
          "CREATE_TRUNC",
          "TRUNCATE_FILE",
          "REMOVE",
          "LINK",
          "RENAME",
          "MKDIR",
          "RMDIR",
          "SYMLINK",
          "SET_DMATTRS",
          "GROWFS",
          "STRAT_WRITE",
          "DIOSTRAT",
          "WRITE_SYNC",
          "WRITEID",
          "ADDAFORK",
          "ATTRINVAL",
          "ATRUNCATE",
          "ATTR_SET",
          "ATTR_RM",
          "ATTR_FLAG",
          "CLEAR_AGI_BUCKET",
          "QM_SBCHANGE",
          "DUMMY1",
          "DUMMY2",
          "QM_QUOTAOFF",
          "QM_DQALLOC",
          "QM_SETQLIM",
          "QM_DQCLUSTER",
          "QM_QINOCREATE",
          "QM_QUOTAOFF_END",
          "SB_UNIT",
          "FSYNC_TS",
          "GROWFSRT_ALLOC",
          "GROWFSRT_ZERO",
          "GROWFSRT_FREE",
          "SWAPEXT"
      };

      xfs_fs_cmn_err(CE_WARN, mp,
                  "xfs_log_write: reservation summary:\n"
                  "  trans type  = %s (%u)\n"
                  "  unit res    = %d bytes\n"
                  "  current res = %d bytes\n"
                  "  total reg   = %u bytes (o/flow = %u bytes)\n"
                  "  ophdrs      = %u (ophdr space = %u bytes)\n"
                  "  ophdr + reg = %u bytes\n"
                  "  num regions = %u\n",
                  ((ticket->t_trans_type <= 0 ||
                    ticket->t_trans_type > XFS_TRANS_TYPE_MAX) ?
                    "bad-trans-type" : trans_type_str[ticket->t_trans_type-1]),
                  ticket->t_trans_type,
                  ticket->t_unit_res,
                  ticket->t_curr_res,
                  ticket->t_res_arr_sum, ticket->t_res_o_flow,
                  ticket->t_res_num_ophdrs, ophdr_spc,
                  ticket->t_res_arr_sum + 
                  ticket->t_res_o_flow + ophdr_spc,
                  ticket->t_res_num);

      for (i = 0; i < ticket->t_res_num; i++) {
            uint r_type = ticket->t_res_arr[i].r_type; 
            cmn_err(CE_WARN,
                      "region[%u]: %s - %u bytes\n",
                      i, 
                      ((r_type <= 0 || r_type > XLOG_REG_TYPE_MAX) ?
                      "bad-rtype" : res_type_str[r_type-1]),
                      ticket->t_res_arr[i].r_len);
      }
}

/*
 * Write some region out to in-core log
 *
 * This will be called when writing externally provided regions or when
 * writing out a commit record for a given transaction.
 *
 * General algorithm:
 *    1. Find total length of this write.  This may include adding to the
 *          lengths passed in.
 *    2. Check whether we violate the tickets reservation.
 *    3. While writing to this iclog
 *        A. Reserve as much space in this iclog as can get
 *        B. If this is first write, save away start lsn
 *        C. While writing this region:
 *          1. If first write of transaction, write start record
 *          2. Write log operation header (header per region)
 *          3. Find out if we can fit entire region into this iclog
 *          4. Potentially, verify destination memcpy ptr
 *          5. Memcpy (partial) region
 *          6. If partial copy, release iclog; otherwise, continue
 *                copying more regions into current iclog
 *    4. Mark want sync bit (in simulation mode)
 *    5. Release iclog for potential flush to on-disk log.
 *
 * ERRORS:
 * 1. Panic if reservation is overrun.  This should never happen since
 *    reservation amounts are generated internal to the filesystem.
 * NOTES:
 * 1. Tickets are single threaded data structures.
 * 2. The XLOG_END_TRANS & XLOG_CONTINUE_TRANS flags are passed down to the
 *    syncing routine.  When a single log_write region needs to span
 *    multiple in-core logs, the XLOG_CONTINUE_TRANS bit should be set
 *    on all log operation writes which don't contain the end of the
 *    region.  The XLOG_END_TRANS bit is used for the in-core log
 *    operation which contains the end of the continued log_write region.
 * 3. When xlog_state_get_iclog_space() grabs the rest of the current iclog,
 *    we don't really know exactly how much space will be used.  As a result,
 *    we don't update ic_offset until the end when we know exactly how many
 *    bytes have been written out.
 */
STATIC int
xlog_write(xfs_mount_t *      mp,
         xfs_log_iovec_t      reg[],
         int                  nentries,
         xfs_log_ticket_t     tic,
         xfs_lsn_t            *start_lsn,
         xlog_in_core_t **commit_iclog,
         uint                 flags)
{
    xlog_t       *log = mp->m_log;
    xlog_ticket_t    *ticket = (xlog_ticket_t *)tic;
    xlog_in_core_t   *iclog = NULL;  /* ptr to current in-core log */
    xlog_op_header_t *logop_head;    /* ptr to log operation header */
    __psint_t          ptr;        /* copy address into data region */
    int                len;        /* # xlog_write() bytes 2 still copy */
    int                index;      /* region index currently copying */
    int                log_offset;     /* offset (from 0) into data region */
    int                start_rec_copy; /* # bytes to copy for start record */
    int                partial_copy;   /* did we split a region? */
    int                partial_copy_len;/* # bytes copied if split region */
    int                need_copy;        /* # bytes need to memcpy this region */
    int                copy_len;         /* # bytes actually memcpy'ing */
    int                copy_off;         /* # bytes from entry start */
    int                contwr;           /* continued write of in-core log? */
    int                error;
    int                record_cnt = 0, data_cnt = 0;

    partial_copy_len = partial_copy = 0;

    /* Calculate potential maximum space.  Each region gets its own
     * xlog_op_header_t and may need to be double word aligned.
     */
    len = 0;
    if (ticket->t_flags & XLOG_TIC_INITED) {    /* acct for start rec of xact */
      len += sizeof(xlog_op_header_t);
      ticket->t_res_num_ophdrs++;
    }

    for (index = 0; index < nentries; index++) {
      len += sizeof(xlog_op_header_t);        /* each region gets >= 1 */
      ticket->t_res_num_ophdrs++;
      len += reg[index].i_len;
      xlog_tic_add_region(ticket, reg[index].i_len, reg[index].i_type);
    }
    contwr = *start_lsn = 0;

    if (ticket->t_curr_res < len) {
      xlog_print_tic_res(mp, ticket);
#ifdef DEBUG
      xlog_panic(
            "xfs_log_write: reservation ran out. Need to up reservation");
#else
      /* Customer configurable panic */
      xfs_cmn_err(XFS_PTAG_LOGRES, CE_ALERT, mp,
            "xfs_log_write: reservation ran out. Need to up reservation");
      /* If we did not panic, shutdown the filesystem */
      xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
#endif
    } else
      ticket->t_curr_res -= len;

    for (index = 0; index < nentries; ) {
      if ((error = xlog_state_get_iclog_space(log, len, &iclog, ticket,
                                     &contwr, &log_offset)))
            return error;

      ASSERT(log_offset <= iclog->ic_size - 1);
      ptr = (__psint_t) ((char *)iclog->ic_datap+log_offset);

      /* start_lsn is the first lsn written to. That's all we need. */
      if (! *start_lsn)
          *start_lsn = be64_to_cpu(iclog->ic_header.h_lsn);

      /* This loop writes out as many regions as can fit in the amount
       * of space which was allocated by xlog_state_get_iclog_space().
       */
      while (index < nentries) {
          ASSERT(reg[index].i_len % sizeof(__int32_t) == 0);
          ASSERT((__psint_t)ptr % sizeof(__int32_t) == 0);
          start_rec_copy = 0;

          /* If first write for transaction, insert start record.
           * We can't be trying to commit if we are inited.  We can't
           * have any "partial_copy" if we are inited.
           */
          if (ticket->t_flags & XLOG_TIC_INITED) {
            logop_head        = (xlog_op_header_t *)ptr;
            logop_head->oh_tid      = cpu_to_be32(ticket->t_tid);
            logop_head->oh_clientid = ticket->t_clientid;
            logop_head->oh_len      = 0;
            logop_head->oh_flags    = XLOG_START_TRANS;
            logop_head->oh_res2     = 0;
            ticket->t_flags         &= ~XLOG_TIC_INITED;    /* clear bit */
            record_cnt++;

            start_rec_copy = sizeof(xlog_op_header_t);
            xlog_write_adv_cnt(ptr, len, log_offset, start_rec_copy);
          }

          /* Copy log operation header directly into data section */
          logop_head                = (xlog_op_header_t *)ptr;
          logop_head->oh_tid        = cpu_to_be32(ticket->t_tid);
          logop_head->oh_clientid   = ticket->t_clientid;
          logop_head->oh_res2       = 0;

          /* header copied directly */
          xlog_write_adv_cnt(ptr, len, log_offset, sizeof(xlog_op_header_t));

          /* are we copying a commit or unmount record? */
          logop_head->oh_flags = flags;

          /*
           * We've seen logs corrupted with bad transaction client
           * ids.  This makes sure that XFS doesn't generate them on.
           * Turn this into an EIO and shut down the filesystem.
           */
          switch (logop_head->oh_clientid)  {
          case XFS_TRANSACTION:
          case XFS_VOLUME:
          case XFS_LOG:
            break;
          default:
            xfs_fs_cmn_err(CE_WARN, mp,
                "Bad XFS transaction clientid 0x%x in ticket 0x%p",
                logop_head->oh_clientid, tic);
            return XFS_ERROR(EIO);
          }

          /* Partial write last time? => (partial_copy != 0)
           * need_copy is the amount we'd like to copy if everything could
           * fit in the current memcpy.
           */
          need_copy =   reg[index].i_len - partial_copy_len;

          copy_off = partial_copy_len;
          if (need_copy <= iclog->ic_size - log_offset) { /*complete write */
              copy_len = need_copy;
            logop_head->oh_len = cpu_to_be32(copy_len);
            if (partial_copy)
                logop_head->oh_flags|= (XLOG_END_TRANS|XLOG_WAS_CONT_TRANS);
            partial_copy_len = partial_copy = 0;
          } else {                                  /* partial write */
            copy_len = iclog->ic_size - log_offset;
            logop_head->oh_len = cpu_to_be32(copy_len);
            logop_head->oh_flags |= XLOG_CONTINUE_TRANS;
            if (partial_copy)
                  logop_head->oh_flags |= XLOG_WAS_CONT_TRANS;
            partial_copy_len += copy_len;
            partial_copy++;
            len += sizeof(xlog_op_header_t); /* from splitting of region */
            /* account for new log op header */
            ticket->t_curr_res -= sizeof(xlog_op_header_t);
            ticket->t_res_num_ophdrs++;
          }
          xlog_verify_dest_ptr(log, ptr);

          /* copy region */
          ASSERT(copy_len >= 0);
          memcpy((xfs_caddr_t)ptr, reg[index].i_addr + copy_off, copy_len);
          xlog_write_adv_cnt(ptr, len, log_offset, copy_len);

          /* make copy_len total bytes copied, including headers */
          copy_len += start_rec_copy + sizeof(xlog_op_header_t);
          record_cnt++;
          data_cnt += contwr ? copy_len : 0;
          if (partial_copy) {             /* copied partial region */
                /* already marked WANT_SYNC by xlog_state_get_iclog_space */
                xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
                record_cnt = data_cnt = 0;
                if ((error = xlog_state_release_iclog(log, iclog)))
                      return error;
                break;              /* don't increment index */
          } else {                        /* copied entire region */
            index++;
            partial_copy_len = partial_copy = 0;

            if (iclog->ic_size - log_offset <= sizeof(xlog_op_header_t)) {
                xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
                record_cnt = data_cnt = 0;
                spin_lock(&log->l_icloglock);
                xlog_state_want_sync(log, iclog);
                spin_unlock(&log->l_icloglock);
                if (commit_iclog) {
                  ASSERT(flags & XLOG_COMMIT_TRANS);
                  *commit_iclog = iclog;
                } else if ((error = xlog_state_release_iclog(log, iclog)))
                     return error;
                if (index == nentries)
                      return 0;           /* we are done */
                else
                      break;
            }
          } /* if (partial_copy) */
      } /* while (index < nentries) */
    } /* for (index = 0; index < nentries; ) */
    ASSERT(len == 0);

    xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
    if (commit_iclog) {
      ASSERT(flags & XLOG_COMMIT_TRANS);
      *commit_iclog = iclog;
      return 0;
    }
    return xlog_state_release_iclog(log, iclog);
}     /* xlog_write */


/*****************************************************************************
 *
 *          State Machine functions
 *
 *****************************************************************************
 */

/* Clean iclogs starting from the head.  This ordering must be
 * maintained, so an iclog doesn't become ACTIVE beyond one that
 * is SYNCING.  This is also required to maintain the notion that we use
 * a ordered wait queue to hold off would be writers to the log when every
 * iclog is trying to sync to disk.
 *
 * State Change: DIRTY -> ACTIVE
 */
STATIC void
xlog_state_clean_log(xlog_t *log)
{
      xlog_in_core_t    *iclog;
      int changed = 0;

      iclog = log->l_iclog;
      do {
            if (iclog->ic_state == XLOG_STATE_DIRTY) {
                  iclog->ic_state   = XLOG_STATE_ACTIVE;
                  iclog->ic_offset       = 0;
                  ASSERT(iclog->ic_callback == NULL);
                  /*
                   * If the number of ops in this iclog indicate it just
                   * contains the dummy transaction, we can
                   * change state into IDLE (the second time around).
                   * Otherwise we should change the state into
                   * NEED a dummy.
                   * We don't need to cover the dummy.
                   */
                  if (!changed &&
                     (be32_to_cpu(iclog->ic_header.h_num_logops) ==
                              XLOG_COVER_OPS)) {
                        changed = 1;
                  } else {
                        /*
                         * We have two dirty iclogs so start over
                         * This could also be num of ops indicates
                         * this is not the dummy going out.
                         */
                        changed = 2;
                  }
                  iclog->ic_header.h_num_logops = 0;
                  memset(iclog->ic_header.h_cycle_data, 0,
                        sizeof(iclog->ic_header.h_cycle_data));
                  iclog->ic_header.h_lsn = 0;
            } else if (iclog->ic_state == XLOG_STATE_ACTIVE)
                  /* do nothing */;
            else
                  break;      /* stop cleaning */
            iclog = iclog->ic_next;
      } while (iclog != log->l_iclog);

      /* log is locked when we are called */
      /*
       * Change state for the dummy log recording.
       * We usually go to NEED. But we go to NEED2 if the changed indicates
       * we are done writing the dummy record.
       * If we are done with the second dummy recored (DONE2), then
       * we go to IDLE.
       */
      if (changed) {
            switch (log->l_covered_state) {
            case XLOG_STATE_COVER_IDLE:
            case XLOG_STATE_COVER_NEED:
            case XLOG_STATE_COVER_NEED2:
                  log->l_covered_state = XLOG_STATE_COVER_NEED;
                  break;

            case XLOG_STATE_COVER_DONE:
                  if (changed == 1)
                        log->l_covered_state = XLOG_STATE_COVER_NEED2;
                  else
                        log->l_covered_state = XLOG_STATE_COVER_NEED;
                  break;

            case XLOG_STATE_COVER_DONE2:
                  if (changed == 1)
                        log->l_covered_state = XLOG_STATE_COVER_IDLE;
                  else
                        log->l_covered_state = XLOG_STATE_COVER_NEED;
                  break;

            default:
                  ASSERT(0);
            }
      }
}     /* xlog_state_clean_log */

STATIC xfs_lsn_t
xlog_get_lowest_lsn(
      xlog_t            *log)
{
      xlog_in_core_t  *lsn_log;
      xfs_lsn_t   lowest_lsn, lsn;

      lsn_log = log->l_iclog;
      lowest_lsn = 0;
      do {
          if (!(lsn_log->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_DIRTY))) {
            lsn = be64_to_cpu(lsn_log->ic_header.h_lsn);
            if ((lsn && !lowest_lsn) ||
                (XFS_LSN_CMP(lsn, lowest_lsn) < 0)) {
                  lowest_lsn = lsn;
            }
          }
          lsn_log = lsn_log->ic_next;
      } while (lsn_log != log->l_iclog);
      return lowest_lsn;
}


STATIC void
xlog_state_do_callback(
      xlog_t            *log,
      int         aborted,
      xlog_in_core_t    *ciclog)
{
      xlog_in_core_t       *iclog;
      xlog_in_core_t       *first_iclog;  /* used to know when we've
                                     * processed all iclogs once */
      xfs_log_callback_t *cb, *cb_next;
      int            flushcnt = 0;
      xfs_lsn_t      lowest_lsn;
      int            ioerrors;      /* counter: iclogs with errors */
      int            loopdidcallbacks; /* flag: inner loop did callbacks*/
      int            funcdidcallbacks; /* flag: function did callbacks */
      int            repeats; /* for issuing console warnings if
                               * looping too many times */
      int            wake = 0;

      spin_lock(&log->l_icloglock);
      first_iclog = iclog = log->l_iclog;
      ioerrors = 0;
      funcdidcallbacks = 0;
      repeats = 0;

      do {
            /*
             * Scan all iclogs starting with the one pointed to by the
             * log.  Reset this starting point each time the log is
             * unlocked (during callbacks).
             *
             * Keep looping through iclogs until one full pass is made
             * without running any callbacks.
             */
            first_iclog = log->l_iclog;
            iclog = log->l_iclog;
            loopdidcallbacks = 0;
            repeats++;

            do {

                  /* skip all iclogs in the ACTIVE & DIRTY states */
                  if (iclog->ic_state &
                      (XLOG_STATE_ACTIVE|XLOG_STATE_DIRTY)) {
                        iclog = iclog->ic_next;
                        continue;
                  }

                  /*
                   * Between marking a filesystem SHUTDOWN and stopping
                   * the log, we do flush all iclogs to disk (if there
                   * wasn't a log I/O error). So, we do want things to
                   * go smoothly in case of just a SHUTDOWN  w/o a
                   * LOG_IO_ERROR.
                   */
                  if (!(iclog->ic_state & XLOG_STATE_IOERROR)) {
                        /*
                         * Can only perform callbacks in order.  Since
                         * this iclog is not in the DONE_SYNC/
                         * DO_CALLBACK state, we skip the rest and
                         * just try to clean up.  If we set our iclog
                         * to DO_CALLBACK, we will not process it when
                         * we retry since a previous iclog is in the
                         * CALLBACK and the state cannot change since
                         * we are holding the l_icloglock.
                         */
                        if (!(iclog->ic_state &
                              (XLOG_STATE_DONE_SYNC |
                                     XLOG_STATE_DO_CALLBACK))) {
                              if (ciclog && (ciclog->ic_state ==
                                          XLOG_STATE_DONE_SYNC)) {
                                    ciclog->ic_state = XLOG_STATE_DO_CALLBACK;
                              }
                              break;
                        }
                        /*
                         * We now have an iclog that is in either the
                         * DO_CALLBACK or DONE_SYNC states. The other
                         * states (WANT_SYNC, SYNCING, or CALLBACK were
                         * caught by the above if and are going to
                         * clean (i.e. we aren't doing their callbacks)
                         * see the above if.
                         */

                        /*
                         * We will do one more check here to see if we
                         * have chased our tail around.
                         */

                        lowest_lsn = xlog_get_lowest_lsn(log);
                        if (lowest_lsn &&
                            XFS_LSN_CMP(lowest_lsn,
                                    be64_to_cpu(iclog->ic_header.h_lsn)) < 0) {
                              iclog = iclog->ic_next;
                              continue; /* Leave this iclog for
                                       * another thread */
                        }

                        iclog->ic_state = XLOG_STATE_CALLBACK;

                        spin_unlock(&log->l_icloglock);

                        /* l_last_sync_lsn field protected by
                         * l_grant_lock. Don't worry about iclog's lsn.
                         * No one else can be here except us.
                         */
                        spin_lock(&log->l_grant_lock);
                        ASSERT(XFS_LSN_CMP(log->l_last_sync_lsn,
                               be64_to_cpu(iclog->ic_header.h_lsn)) <= 0);
                        log->l_last_sync_lsn =
                              be64_to_cpu(iclog->ic_header.h_lsn);
                        spin_unlock(&log->l_grant_lock);

                  } else {
                        spin_unlock(&log->l_icloglock);
                        ioerrors++;
                  }

                  /*
                   * Keep processing entries in the callback list until
                   * we come around and it is empty.  We need to
                   * atomically see that the list is empty and change the
                   * state to DIRTY so that we don't miss any more
                   * callbacks being added.
                   */
                  spin_lock(&iclog->ic_callback_lock);
                  cb = iclog->ic_callback;
                  while (cb) {
                        iclog->ic_callback_tail = &(iclog->ic_callback);
                        iclog->ic_callback = NULL;
                        spin_unlock(&iclog->ic_callback_lock);

                        /* perform callbacks in the order given */
                        for (; cb; cb = cb_next) {
                              cb_next = cb->cb_next;
                              cb->cb_func(cb->cb_arg, aborted);
                        }
                        spin_lock(&iclog->ic_callback_lock);
                        cb = iclog->ic_callback;
                  }

                  loopdidcallbacks++;
                  funcdidcallbacks++;

                  spin_lock(&log->l_icloglock);
                  ASSERT(iclog->ic_callback == NULL);
                  spin_unlock(&iclog->ic_callback_lock);
                  if (!(iclog->ic_state & XLOG_STATE_IOERROR))
                        iclog->ic_state = XLOG_STATE_DIRTY;

                  /*
                   * Transition from DIRTY to ACTIVE if applicable.
                   * NOP if STATE_IOERROR.
                   */
                  xlog_state_clean_log(log);

                  /* wake up threads waiting in xfs_log_force() */
                  sv_broadcast(&iclog->ic_force_wait);

                  iclog = iclog->ic_next;
            } while (first_iclog != iclog);

            if (repeats > 5000) {
                  flushcnt += repeats;
                  repeats = 0;
                  xfs_fs_cmn_err(CE_WARN, log->l_mp,
                        "%s: possible infinite loop (%d iterations)",
                        __func__, flushcnt);
            }
      } while (!ioerrors && loopdidcallbacks);

      /*
       * make one last gasp attempt to see if iclogs are being left in
       * limbo..
       */
#ifdef DEBUG
      if (funcdidcallbacks) {
            first_iclog = iclog = log->l_iclog;
            do {
                  ASSERT(iclog->ic_state != XLOG_STATE_DO_CALLBACK);
                  /*
                   * Terminate the loop if iclogs are found in states
                   * which will cause other threads to clean up iclogs.
                   *
                   * SYNCING - i/o completion will go through logs
                   * DONE_SYNC - interrupt thread should be waiting for
                   *              l_icloglock
                   * IOERROR - give up hope all ye who enter here
                   */
                  if (iclog->ic_state == XLOG_STATE_WANT_SYNC ||
                      iclog->ic_state == XLOG_STATE_SYNCING ||
                      iclog->ic_state == XLOG_STATE_DONE_SYNC ||
                      iclog->ic_state == XLOG_STATE_IOERROR )
                        break;
                  iclog = iclog->ic_next;
            } while (first_iclog != iclog);
      }
#endif

      if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR))
            wake = 1;
      spin_unlock(&log->l_icloglock);

      if (wake)
            sv_broadcast(&log->l_flush_wait);
}


/*
 * Finish transitioning this iclog to the dirty state.
 *
 * Make sure that we completely execute this routine only when this is
 * the last call to the iclog.  There is a good chance that iclog flushes,
 * when we reach the end of the physical log, get turned into 2 separate
 * calls to bwrite.  Hence, one iclog flush could generate two calls to this
 * routine.  By using the reference count bwritecnt, we guarantee that only
 * the second completion goes through.
 *
 * Callbacks could take time, so they are done outside the scope of the
 * global state machine log lock.
 */
STATIC void
xlog_state_done_syncing(
      xlog_in_core_t    *iclog,
      int         aborted)
{
      xlog_t               *log = iclog->ic_log;

      spin_lock(&log->l_icloglock);

      ASSERT(iclog->ic_state == XLOG_STATE_SYNCING ||
             iclog->ic_state == XLOG_STATE_IOERROR);
      ASSERT(atomic_read(&iclog->ic_refcnt) == 0);
      ASSERT(iclog->ic_bwritecnt == 1 || iclog->ic_bwritecnt == 2);


      /*
       * If we got an error, either on the first buffer, or in the case of
       * split log writes, on the second, we mark ALL iclogs STATE_IOERROR,
       * and none should ever be attempted to be written to disk
       * again.
       */
      if (iclog->ic_state != XLOG_STATE_IOERROR) {
            if (--iclog->ic_bwritecnt == 1) {
                  spin_unlock(&log->l_icloglock);
                  return;
            }
            iclog->ic_state = XLOG_STATE_DONE_SYNC;
      }

      /*
       * Someone could be sleeping prior to writing out the next
       * iclog buffer, we wake them all, one will get to do the
       * I/O, the others get to wait for the result.
       */
      sv_broadcast(&iclog->ic_write_wait);
      spin_unlock(&log->l_icloglock);
      xlog_state_do_callback(log, aborted, iclog);    /* also cleans log */
}     /* xlog_state_done_syncing */


/*
 * If the head of the in-core log ring is not (ACTIVE or DIRTY), then we must
 * sleep.  We wait on the flush queue on the head iclog as that should be
 * the first iclog to complete flushing. Hence if all iclogs are syncing,
 * we will wait here and all new writes will sleep until a sync completes.
 *
 * The in-core logs are used in a circular fashion. They are not used
 * out-of-order even when an iclog past the head is free.
 *
 * return:
 *    * log_offset where xlog_write() can start writing into the in-core
 *          log's data space.
 *    * in-core log pointer to which xlog_write() should write.
 *    * boolean indicating this is a continued write to an in-core log.
 *          If this is the last write, then the in-core log's offset field
 *          needs to be incremented, depending on the amount of data which
 *          is copied.
 */
STATIC int
xlog_state_get_iclog_space(xlog_t     *log,
                     int              len,
                     xlog_in_core_t **iclogp,
                     xlog_ticket_t  *ticket,
                     int              *continued_write,
                     int              *logoffsetp)
{
      int           log_offset;
      xlog_rec_header_t *head;
      xlog_in_core_t      *iclog;
      int           error;

restart:
      spin_lock(&log->l_icloglock);
      if (XLOG_FORCED_SHUTDOWN(log)) {
            spin_unlock(&log->l_icloglock);
            return XFS_ERROR(EIO);
      }

      iclog = log->l_iclog;
      if (iclog->ic_state != XLOG_STATE_ACTIVE) {
            xlog_trace_iclog(iclog, XLOG_TRACE_SLEEP_FLUSH);
            XFS_STATS_INC(xs_log_noiclogs);

            /* Wait for log writes to have flushed */
            sv_wait(&log->l_flush_wait, 0, &log->l_icloglock, 0);
            goto restart;
      }

      head = &iclog->ic_header;

      atomic_inc(&iclog->ic_refcnt);      /* prevents sync */
      log_offset = iclog->ic_offset;

      /* On the 1st write to an iclog, figure out lsn.  This works
       * if iclogs marked XLOG_STATE_WANT_SYNC always write out what they are
       * committing to.  If the offset is set, that's how many blocks
       * must be written.
       */
      if (log_offset == 0) {
            ticket->t_curr_res -= log->l_iclog_hsize;
            xlog_tic_add_region(ticket,
                            log->l_iclog_hsize,
                            XLOG_REG_TYPE_LRHEADER);
            head->h_cycle = cpu_to_be32(log->l_curr_cycle);
            head->h_lsn = cpu_to_be64(
                  xlog_assign_lsn(log->l_curr_cycle, log->l_curr_block));
            ASSERT(log->l_curr_block >= 0);
      }

      /* If there is enough room to write everything, then do it.  Otherwise,
       * claim the rest of the region and make sure the XLOG_STATE_WANT_SYNC
       * bit is on, so this will get flushed out.  Don't update ic_offset
       * until you know exactly how many bytes get copied.  Therefore, wait
       * until later to update ic_offset.
       *
       * xlog_write() algorithm assumes that at least 2 xlog_op_header_t's
       * can fit into remaining data section.
       */
      if (iclog->ic_size - iclog->ic_offset < 2*sizeof(xlog_op_header_t)) {
            xlog_state_switch_iclogs(log, iclog, iclog->ic_size);

            /*
             * If I'm the only one writing to this iclog, sync it to disk.
             * We need to do an atomic compare and decrement here to avoid
             * racing with concurrent atomic_dec_and_lock() calls in
             * xlog_state_release_iclog() when there is more than one
             * reference to the iclog.
             */
            if (!atomic_add_unless(&iclog->ic_refcnt, -1, 1)) {
                  /* we are the only one */
                  spin_unlock(&log->l_icloglock);
                  error = xlog_state_release_iclog(log, iclog);
                  if (error)
                        return error;
            } else {
                  spin_unlock(&log->l_icloglock);
            }
            goto restart;
      }

      /* Do we have enough room to write the full amount in the remainder
       * of this iclog?  Or must we continue a write on the next iclog and
       * mark this iclog as completely taken?  In the case where we switch
       * iclogs (to mark it taken), this particular iclog will release/sync
       * to disk in xlog_write().
       */
      if (len <= iclog->ic_size - iclog->ic_offset) {
            *continued_write = 0;
            iclog->ic_offset += len;
      } else {
            *continued_write = 1;
            xlog_state_switch_iclogs(log, iclog, iclog->ic_size);
      }
      *iclogp = iclog;

      ASSERT(iclog->ic_offset <= iclog->ic_size);
      spin_unlock(&log->l_icloglock);

      *logoffsetp = log_offset;
      return 0;
}     /* xlog_state_get_iclog_space */

/*
 * Atomically get the log space required for a log ticket.
 *
 * Once a ticket gets put onto the reserveq, it will only return after
 * the needed reservation is satisfied.
 */
STATIC int
xlog_grant_log_space(xlog_t      *log,
                 xlog_ticket_t *tic)
{
      int          free_bytes;
      int          need_bytes;
#ifdef DEBUG
      xfs_lsn_t    tail_lsn;
#endif


#ifdef DEBUG
      if (log->l_flags & XLOG_ACTIVE_RECOVERY)
            panic("grant Recovery problem");
#endif

      /* Is there space or do we need to sleep? */
      spin_lock(&log->l_grant_lock);
      xlog_trace_loggrant(log, tic, "xlog_grant_log_space: enter");

      /* something is already sleeping; insert new transaction at end */
      if (log->l_reserve_headq) {
            xlog_ins_ticketq(&log->l_reserve_headq, tic);
            xlog_trace_loggrant(log, tic,
                            "xlog_grant_log_space: sleep 1");
            /*
             * Gotta check this before going to sleep, while we're
             * holding the grant lock.
             */
            if (XLOG_FORCED_SHUTDOWN(log))
                  goto error_return;

            XFS_STATS_INC(xs_sleep_logspace);
            sv_wait(&tic->t_wait, PINOD|PLTWAIT, &log->l_grant_lock, s);
            /*
             * If we got an error, and the filesystem is shutting down,
             * we'll catch it down below. So just continue...
             */
            xlog_trace_loggrant(log, tic,
                            "xlog_grant_log_space: wake 1");
            spin_lock(&log->l_grant_lock);
      }
      if (tic->t_flags & XFS_LOG_PERM_RESERV)
            need_bytes = tic->t_unit_res*tic->t_ocnt;
      else
            need_bytes = tic->t_unit_res;

redo:
      if (XLOG_FORCED_SHUTDOWN(log))
            goto error_return;

      free_bytes = xlog_space_left(log, log->l_grant_reserve_cycle,
                             log->l_grant_reserve_bytes);
      if (free_bytes < need_bytes) {
            if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
                  xlog_ins_ticketq(&log->l_reserve_headq, tic);
            xlog_trace_loggrant(log, tic,
                            "xlog_grant_log_space: sleep 2");
            spin_unlock(&log->l_grant_lock);
            xlog_grant_push_ail(log->l_mp, need_bytes);
            spin_lock(&log->l_grant_lock);

            XFS_STATS_INC(xs_sleep_logspace);
            sv_wait(&tic->t_wait, PINOD|PLTWAIT, &log->l_grant_lock, s);

            spin_lock(&log->l_grant_lock);
            if (XLOG_FORCED_SHUTDOWN(log))
                  goto error_return;

            xlog_trace_loggrant(log, tic,
                            "xlog_grant_log_space: wake 2");
            goto redo;
      } else if (tic->t_flags & XLOG_TIC_IN_Q)
            xlog_del_ticketq(&log->l_reserve_headq, tic);

      /* we've got enough space */
      xlog_grant_add_space(log, need_bytes);
#ifdef DEBUG
      tail_lsn = log->l_tail_lsn;
      /*
       * Check to make sure the grant write head didn't just over lap the
       * tail.  If the cycles are the same, we can't be overlapping.
       * Otherwise, make sure that the cycles differ by exactly one and
       * check the byte count.
       */
      if (CYCLE_LSN(tail_lsn) != log->l_grant_write_cycle) {
            ASSERT(log->l_grant_write_cycle-1 == CYCLE_LSN(tail_lsn));
            ASSERT(log->l_grant_write_bytes <= BBTOB(BLOCK_LSN(tail_lsn)));
      }
#endif
      xlog_trace_loggrant(log, tic, "xlog_grant_log_space: exit");
      xlog_verify_grant_head(log, 1);
      spin_unlock(&log->l_grant_lock);
      return 0;

 error_return:
      if (tic->t_flags & XLOG_TIC_IN_Q)
            xlog_del_ticketq(&log->l_reserve_headq, tic);
      xlog_trace_loggrant(log, tic, "xlog_grant_log_space: err_ret");
      /*
       * If we are failing, make sure the ticket doesn't have any
       * current reservations. We don't want to add this back when
       * the ticket/transaction gets cancelled.
       */
      tic->t_curr_res = 0;
      tic->t_cnt = 0; /* ungrant will give back unit_res * t_cnt. */
      spin_unlock(&log->l_grant_lock);
      return XFS_ERROR(EIO);
}     /* xlog_grant_log_space */


/*
 * Replenish the byte reservation required by moving the grant write head.
 *
 *
 */
STATIC int
xlog_regrant_write_log_space(xlog_t    *log,
                       xlog_ticket_t *tic)
{
      int         free_bytes, need_bytes;
      xlog_ticket_t     *ntic;
#ifdef DEBUG
      xfs_lsn_t   tail_lsn;
#endif

      tic->t_curr_res = tic->t_unit_res;
      xlog_tic_reset_res(tic);

      if (tic->t_cnt > 0)
            return 0;

#ifdef DEBUG
      if (log->l_flags & XLOG_ACTIVE_RECOVERY)
            panic("regrant Recovery problem");
#endif

      spin_lock(&log->l_grant_lock);
      xlog_trace_loggrant(log, tic, "xlog_regrant_write_log_space: enter");

      if (XLOG_FORCED_SHUTDOWN(log))
            goto error_return;

      /* If there are other waiters on the queue then give them a
       * chance at logspace before us. Wake up the first waiters,
       * if we do not wake up all the waiters then go to sleep waiting
       * for more free space, otherwise try to get some space for
       * this transaction.
       */
      need_bytes = tic->t_unit_res;
      if ((ntic = log->l_write_headq)) {
            free_bytes = xlog_space_left(log, log->l_grant_write_cycle,
                                   log->l_grant_write_bytes);
            do {
                  ASSERT(ntic->t_flags & XLOG_TIC_PERM_RESERV);

                  if (free_bytes < ntic->t_unit_res)
                        break;
                  free_bytes -= ntic->t_unit_res;
                  sv_signal(&ntic->t_wait);
                  ntic = ntic->t_next;
            } while (ntic != log->l_write_headq);

            if (ntic != log->l_write_headq) {
                  if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
                        xlog_ins_ticketq(&log->l_write_headq, tic);

                  xlog_trace_loggrant(log, tic,
                            "xlog_regrant_write_log_space: sleep 1");
                  spin_unlock(&log->l_grant_lock);
                  xlog_grant_push_ail(log->l_mp, need_bytes);
                  spin_lock(&log->l_grant_lock);

                  XFS_STATS_INC(xs_sleep_logspace);
                  sv_wait(&tic->t_wait, PINOD|PLTWAIT,
                        &log->l_grant_lock, s);

                  /* If we're shutting down, this tic is already
                   * off the queue */
                  spin_lock(&log->l_grant_lock);
                  if (XLOG_FORCED_SHUTDOWN(log))
                        goto error_return;

                  xlog_trace_loggrant(log, tic,
                            "xlog_regrant_write_log_space: wake 1");
            }
      }

redo:
      if (XLOG_FORCED_SHUTDOWN(log))
            goto error_return;

      free_bytes = xlog_space_left(log, log->l_grant_write_cycle,
                             log->l_grant_write_bytes);
      if (free_bytes < need_bytes) {
            if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
                  xlog_ins_ticketq(&log->l_write_headq, tic);
            spin_unlock(&log->l_grant_lock);
            xlog_grant_push_ail(log->l_mp, need_bytes);
            spin_lock(&log->l_grant_lock);

            XFS_STATS_INC(xs_sleep_logspace);
            sv_wait(&tic->t_wait, PINOD|PLTWAIT, &log->l_grant_lock, s);

            /* If we're shutting down, this tic is already off the queue */
            spin_lock(&log->l_grant_lock);
            if (XLOG_FORCED_SHUTDOWN(log))
                  goto error_return;

            xlog_trace_loggrant(log, tic,
                            "xlog_regrant_write_log_space: wake 2");
            goto redo;
      } else if (tic->t_flags & XLOG_TIC_IN_Q)
            xlog_del_ticketq(&log->l_write_headq, tic);

      /* we've got enough space */
      xlog_grant_add_space_write(log, need_bytes);
#ifdef DEBUG
      tail_lsn = log->l_tail_lsn;
      if (CYCLE_LSN(tail_lsn) != log->l_grant_write_cycle) {
            ASSERT(log->l_grant_write_cycle-1 == CYCLE_LSN(tail_lsn));
            ASSERT(log->l_grant_write_bytes <= BBTOB(BLOCK_LSN(tail_lsn)));
      }
#endif

      xlog_trace_loggrant(log, tic, "xlog_regrant_write_log_space: exit");
      xlog_verify_grant_head(log, 1);
      spin_unlock(&log->l_grant_lock);
      return 0;


 error_return:
      if (tic->t_flags & XLOG_TIC_IN_Q)
            xlog_del_ticketq(&log->l_reserve_headq, tic);
      xlog_trace_loggrant(log, tic, "xlog_regrant_write_log_space: err_ret");
      /*
       * If we are failing, make sure the ticket doesn't have any
       * current reservations. We don't want to add this back when
       * the ticket/transaction gets cancelled.
       */
      tic->t_curr_res = 0;
      tic->t_cnt = 0; /* ungrant will give back unit_res * t_cnt. */
      spin_unlock(&log->l_grant_lock);
      return XFS_ERROR(EIO);
}     /* xlog_regrant_write_log_space */


/* The first cnt-1 times through here we don't need to
 * move the grant write head because the permanent
 * reservation has reserved cnt times the unit amount.
 * Release part of current permanent unit reservation and
 * reset current reservation to be one units worth.  Also
 * move grant reservation head forward.
 */
STATIC void
xlog_regrant_reserve_log_space(xlog_t          *log,
                         xlog_ticket_t *ticket)
{
      xlog_trace_loggrant(log, ticket,
                      "xlog_regrant_reserve_log_space: enter");
      if (ticket->t_cnt > 0)
            ticket->t_cnt--;

      spin_lock(&log->l_grant_lock);
      xlog_grant_sub_space(log, ticket->t_curr_res);
      ticket->t_curr_res = ticket->t_unit_res;
      xlog_tic_reset_res(ticket);
      xlog_trace_loggrant(log, ticket,
                      "xlog_regrant_reserve_log_space: sub current res");
      xlog_verify_grant_head(log, 1);

      /* just return if we still have some of the pre-reserved space */
      if (ticket->t_cnt > 0) {
            spin_unlock(&log->l_grant_lock);
            return;
      }

      xlog_grant_add_space_reserve(log, ticket->t_unit_res);
      xlog_trace_loggrant(log, ticket,
                      "xlog_regrant_reserve_log_space: exit");
      xlog_verify_grant_head(log, 0);
      spin_unlock(&log->l_grant_lock);
      ticket->t_curr_res = ticket->t_unit_res;
      xlog_tic_reset_res(ticket);
}     /* xlog_regrant_reserve_log_space */


/*
 * Give back the space left from a reservation.
 *
 * All the information we need to make a correct determination of space left
 * is present.  For non-permanent reservations, things are quite easy.  The
 * count should have been decremented to zero.  We only need to deal with the
 * space remaining in the current reservation part of the ticket.  If the
 * ticket contains a permanent reservation, there may be left over space which
 * needs to be released.  A count of N means that N-1 refills of the current
 * reservation can be done before we need to ask for more space.  The first
 * one goes to fill up the first current reservation.  Once we run out of
 * space, the count will stay at zero and the only space remaining will be
 * in the current reservation field.
 */
STATIC void
xlog_ungrant_log_space(xlog_t      *log,
                   xlog_ticket_t *ticket)
{
      if (ticket->t_cnt > 0)
            ticket->t_cnt--;

      spin_lock(&log->l_grant_lock);
      xlog_trace_loggrant(log, ticket, "xlog_ungrant_log_space: enter");

      xlog_grant_sub_space(log, ticket->t_curr_res);

      xlog_trace_loggrant(log, ticket, "xlog_ungrant_log_space: sub current");

      /* If this is a permanent reservation ticket, we may be able to free
       * up more space based on the remaining count.
       */
      if (ticket->t_cnt > 0) {
            ASSERT(ticket->t_flags & XLOG_TIC_PERM_RESERV);
            xlog_grant_sub_space(log, ticket->t_unit_res*ticket->t_cnt);
      }

      xlog_trace_loggrant(log, ticket, "xlog_ungrant_log_space: exit");
      xlog_verify_grant_head(log, 1);
      spin_unlock(&log->l_grant_lock);
      xfs_log_move_tail(log->l_mp, 1);
}     /* xlog_ungrant_log_space */


/*
 * Flush iclog to disk if this is the last reference to the given iclog and
 * the WANT_SYNC bit is set.
 *
 * When this function is entered, the iclog is not necessarily in the
 * WANT_SYNC state.  It may be sitting around waiting to get filled.
 *
 *
 */
STATIC int
xlog_state_release_iclog(
      xlog_t            *log,
      xlog_in_core_t    *iclog)
{
      int         sync = 0;   /* do we sync? */

      if (iclog->ic_state & XLOG_STATE_IOERROR)
            return XFS_ERROR(EIO);

      ASSERT(atomic_read(&iclog->ic_refcnt) > 0);
      if (!atomic_dec_and_lock(&iclog->ic_refcnt, &log->l_icloglock))
            return 0;

      if (iclog->ic_state & XLOG_STATE_IOERROR) {
            spin_unlock(&log->l_icloglock);
            return XFS_ERROR(EIO);
      }
      ASSERT(iclog->ic_state == XLOG_STATE_ACTIVE ||
             iclog->ic_state == XLOG_STATE_WANT_SYNC);

      if (iclog->ic_state == XLOG_STATE_WANT_SYNC) {
            /* update tail before writing to iclog */
            xlog_assign_tail_lsn(log->l_mp);
            sync++;
            iclog->ic_state = XLOG_STATE_SYNCING;
            iclog->ic_header.h_tail_lsn = cpu_to_be64(log->l_tail_lsn);
            xlog_verify_tail_lsn(log, iclog, log->l_tail_lsn);
            /* cycle incremented when incrementing curr_block */
      }
      spin_unlock(&log->l_icloglock);

      /*
       * We let the log lock go, so it's possible that we hit a log I/O
       * error or some other SHUTDOWN condition that marks the iclog
       * as XLOG_STATE_IOERROR before the bwrite. However, we know that
       * this iclog has consistent data, so we ignore IOERROR
       * flags after this point.
       */
      if (sync)
            return xlog_sync(log, iclog);
      return 0;
}     /* xlog_state_release_iclog */


/*
 * This routine will mark the current iclog in the ring as WANT_SYNC
 * and move the current iclog pointer to the next iclog in the ring.
 * When this routine is called from xlog_state_get_iclog_space(), the
 * exact size of the iclog has not yet been determined.  All we know is
 * that every data block.  We have run out of space in this log record.
 */
STATIC void
xlog_state_switch_iclogs(xlog_t           *log,
                   xlog_in_core_t *iclog,
                   int        eventual_size)
{
      ASSERT(iclog->ic_state == XLOG_STATE_ACTIVE);
      if (!eventual_size)
            eventual_size = iclog->ic_offset;
      iclog->ic_state = XLOG_STATE_WANT_SYNC;
      iclog->ic_header.h_prev_block = cpu_to_be32(log->l_prev_block);
      log->l_prev_block = log->l_curr_block;
      log->l_prev_cycle = log->l_curr_cycle;

      /* roll log?: ic_offset changed later */
      log->l_curr_block += BTOBB(eventual_size)+BTOBB(log->l_iclog_hsize);

      /* Round up to next log-sunit */
      if (xfs_sb_version_haslogv2(&log->l_mp->m_sb) &&
          log->l_mp->m_sb.sb_logsunit > 1) {
            __uint32_t sunit_bb = BTOBB(log->l_mp->m_sb.sb_logsunit);
            log->l_curr_block = roundup(log->l_curr_block, sunit_bb);
      }

      if (log->l_curr_block >= log->l_logBBsize) {
            log->l_curr_cycle++;
            if (log->l_curr_cycle == XLOG_HEADER_MAGIC_NUM)
                  log->l_curr_cycle++;
            log->l_curr_block -= log->l_logBBsize;
            ASSERT(log->l_curr_block >= 0);
      }
      ASSERT(iclog == log->l_iclog);
      log->l_iclog = iclog->ic_next;
}     /* xlog_state_switch_iclogs */


/*
 * Write out all data in the in-core log as of this exact moment in time.
 *
 * Data may be written to the in-core log during this call.  However,
 * we don't guarantee this data will be written out.  A change from past
 * implementation means this routine will *not* write out zero length LRs.
 *
 * Basically, we try and perform an intelligent scan of the in-core logs.
 * If we determine there is no flushable data, we just return.  There is no
 * flushable data if:
 *
 *    1. the current iclog is active and has no data; the previous iclog
 *          is in the active or dirty state.
 *    2. the current iclog is drity, and the previous iclog is in the
 *          active or dirty state.
 *
 * We may sleep if:
 *
 *    1. the current iclog is not in the active nor dirty state.
 *    2. the current iclog dirty, and the previous iclog is not in the
 *          active nor dirty state.
 *    3. the current iclog is active, and there is another thread writing
 *          to this particular iclog.
 *    4. a) the current iclog is active and has no other writers
 *       b) when we return from flushing out this iclog, it is still
 *          not in the active nor dirty state.
 */
STATIC int
xlog_state_sync_all(xlog_t *log, uint flags, int *log_flushed)
{
      xlog_in_core_t    *iclog;
      xfs_lsn_t   lsn;

      spin_lock(&log->l_icloglock);

      iclog = log->l_iclog;
      if (iclog->ic_state & XLOG_STATE_IOERROR) {
            spin_unlock(&log->l_icloglock);
            return XFS_ERROR(EIO);
      }

      /* If the head iclog is not active nor dirty, we just attach
       * ourselves to the head and go to sleep.
       */
      if (iclog->ic_state == XLOG_STATE_ACTIVE ||
          iclog->ic_state == XLOG_STATE_DIRTY) {
            /*
             * If the head is dirty or (active and empty), then
             * we need to look at the previous iclog.  If the previous
             * iclog is active or dirty we are done.  There is nothing
             * to sync out.  Otherwise, we attach ourselves to the
             * previous iclog and go to sleep.
             */
            if (iclog->ic_state == XLOG_STATE_DIRTY ||
                (atomic_read(&iclog->ic_refcnt) == 0
                 && iclog->ic_offset == 0)) {
                  iclog = iclog->ic_prev;
                  if (iclog->ic_state == XLOG_STATE_ACTIVE ||
                      iclog->ic_state == XLOG_STATE_DIRTY)
                        goto no_sleep;
                  else
                        goto maybe_sleep;
            } else {
                  if (atomic_read(&iclog->ic_refcnt) == 0) {
                        /* We are the only one with access to this
                         * iclog.  Flush it out now.  There should
                         * be a roundoff of zero to show that someone
                         * has already taken care of the roundoff from
                         * the previous sync.
                         */
                        atomic_inc(&iclog->ic_refcnt);
                        lsn = be64_to_cpu(iclog->ic_header.h_lsn);
                        xlog_state_switch_iclogs(log, iclog, 0);
                        spin_unlock(&log->l_icloglock);

                        if (xlog_state_release_iclog(log, iclog))
                              return XFS_ERROR(EIO);
                        *log_flushed = 1;
                        spin_lock(&log->l_icloglock);
                        if (be64_to_cpu(iclog->ic_header.h_lsn) == lsn &&
                            iclog->ic_state != XLOG_STATE_DIRTY)
                              goto maybe_sleep;
                        else
                              goto no_sleep;
                  } else {
                        /* Someone else is writing to this iclog.
                         * Use its call to flush out the data.  However,
                         * the other thread may not force out this LR,
                         * so we mark it WANT_SYNC.
                         */
                        xlog_state_switch_iclogs(log, iclog, 0);
                        goto maybe_sleep;
                  }
            }
      }

      /* By the time we come around again, the iclog could've been filled
       * which would give it another lsn.  If we have a new lsn, just
       * return because the relevant data has been flushed.
       */
maybe_sleep:
      if (flags & XFS_LOG_SYNC) {
            /*
             * We must check if we're shutting down here, before
             * we wait, while we're holding the l_icloglock.
             * Then we check again after waking up, in case our
             * sleep was disturbed by a bad news.
             */
            if (iclog->ic_state & XLOG_STATE_IOERROR) {
                  spin_unlock(&log->l_icloglock);
                  return XFS_ERROR(EIO);
            }
            XFS_STATS_INC(xs_log_force_sleep);
            sv_wait(&iclog->ic_force_wait, PINOD, &log->l_icloglock, s);
            /*
             * No need to grab the log lock here since we're
             * only deciding whether or not to return EIO
             * and the memory read should be atomic.
             */
            if (iclog->ic_state & XLOG_STATE_IOERROR)
                  return XFS_ERROR(EIO);
            *log_flushed = 1;

      } else {

no_sleep:
            spin_unlock(&log->l_icloglock);
      }
      return 0;
}     /* xlog_state_sync_all */


/*
 * Used by code which implements synchronous log forces.
 *
 * Find in-core log with lsn.
 *    If it is in the DIRTY state, just return.
 *    If it is in the ACTIVE state, move the in-core log into the WANT_SYNC
 *          state and go to sleep or return.
 *    If it is in any other state, go to sleep or return.
 *
 * If filesystem activity goes to zero, the iclog will get flushed only by
 * bdflush().
 */
STATIC int
xlog_state_sync(xlog_t    *log,
            xfs_lsn_t lsn,
            uint    flags,
            int     *log_flushed)
{
    xlog_in_core_t      *iclog;
    int                 already_slept = 0;

try_again:
    spin_lock(&log->l_icloglock);
    iclog = log->l_iclog;

    if (iclog->ic_state & XLOG_STATE_IOERROR) {
          spin_unlock(&log->l_icloglock);
          return XFS_ERROR(EIO);
    }

    do {
      if (be64_to_cpu(iclog->ic_header.h_lsn) != lsn) {
            iclog = iclog->ic_next;
            continue;
      }

      if (iclog->ic_state == XLOG_STATE_DIRTY) {
            spin_unlock(&log->l_icloglock);
            return 0;
      }

      if (iclog->ic_state == XLOG_STATE_ACTIVE) {
            /*
             * We sleep here if we haven't already slept (e.g.
             * this is the first time we've looked at the correct
             * iclog buf) and the buffer before us is going to
             * be sync'ed. The reason for this is that if we
             * are doing sync transactions here, by waiting for
             * the previous I/O to complete, we can allow a few
             * more transactions into this iclog before we close
             * it down.
             *
             * Otherwise, we mark the buffer WANT_SYNC, and bump
             * up the refcnt so we can release the log (which drops
             * the ref count).  The state switch keeps new transaction
             * commits from using this buffer.  When the current commits
             * finish writing into the buffer, the refcount will drop to
             * zero and the buffer will go out then.
             */
            if (!already_slept &&
                (iclog->ic_prev->ic_state & (XLOG_STATE_WANT_SYNC |
                                     XLOG_STATE_SYNCING))) {
                  ASSERT(!(iclog->ic_state & XLOG_STATE_IOERROR));
                  XFS_STATS_INC(xs_log_force_sleep);
                  sv_wait(&iclog->ic_prev->ic_write_wait, PSWP,
                        &log->l_icloglock, s);
                  *log_flushed = 1;
                  already_slept = 1;
                  goto try_again;
            } else {
                  atomic_inc(&iclog->ic_refcnt);
                  xlog_state_switch_iclogs(log, iclog, 0);
                  spin_unlock(&log->l_icloglock);
                  if (xlog_state_release_iclog(log, iclog))
                        return XFS_ERROR(EIO);
                  *log_flushed = 1;
                  spin_lock(&log->l_icloglock);
            }
      }

      if ((flags & XFS_LOG_SYNC) && /* sleep */
          !(iclog->ic_state & (XLOG_STATE_ACTIVE | XLOG_STATE_DIRTY))) {

            /*
             * Don't wait on completion if we know that we've
             * gotten a log write error.
             */
            if (iclog->ic_state & XLOG_STATE_IOERROR) {
                  spin_unlock(&log->l_icloglock);
                  return XFS_ERROR(EIO);
            }
            XFS_STATS_INC(xs_log_force_sleep);
            sv_wait(&iclog->ic_force_wait, PSWP, &log->l_icloglock, s);
            /*
             * No need to grab the log lock here since we're
             * only deciding whether or not to return EIO
             * and the memory read should be atomic.
             */
            if (iclog->ic_state & XLOG_STATE_IOERROR)
                  return XFS_ERROR(EIO);
            *log_flushed = 1;
      } else {          /* just return */
            spin_unlock(&log->l_icloglock);
      }
      return 0;

    } while (iclog != log->l_iclog);

    spin_unlock(&log->l_icloglock);
    return 0;
}     /* xlog_state_sync */


/*
 * Called when we want to mark the current iclog as being ready to sync to
 * disk.
 */
STATIC void
xlog_state_want_sync(xlog_t *log, xlog_in_core_t *iclog)
{
      assert_spin_locked(&log->l_icloglock);

      if (iclog->ic_state == XLOG_STATE_ACTIVE) {
            xlog_state_switch_iclogs(log, iclog, 0);
      } else {
            ASSERT(iclog->ic_state &
                  (XLOG_STATE_WANT_SYNC|XLOG_STATE_IOERROR));
      }
}


/*****************************************************************************
 *
 *          TICKET functions
 *
 *****************************************************************************
 */

/*
 * Free a used ticket when its refcount falls to zero.
 */
void
xfs_log_ticket_put(
      xlog_ticket_t     *ticket)
{
      ASSERT(atomic_read(&ticket->t_ref) > 0);
      if (atomic_dec_and_test(&ticket->t_ref)) {
            sv_destroy(&ticket->t_wait);
            kmem_zone_free(xfs_log_ticket_zone, ticket);
      }
}

xlog_ticket_t *
xfs_log_ticket_get(
      xlog_ticket_t     *ticket)
{
      ASSERT(atomic_read(&ticket->t_ref) > 0);
      atomic_inc(&ticket->t_ref);
      return ticket;
}

/*
 * Allocate and initialise a new log ticket.
 */
STATIC xlog_ticket_t *
xlog_ticket_alloc(xlog_t            *log,
            int         unit_bytes,
            int         cnt,
            char        client,
            uint        xflags)
{
      xlog_ticket_t     *tic;
      uint        num_headers;

      tic = kmem_zone_zalloc(xfs_log_ticket_zone, KM_SLEEP|KM_MAYFAIL);
      if (!tic)
            return NULL;

      /*
       * Permanent reservations have up to 'cnt'-1 active log operations
       * in the log.  A unit in this case is the amount of space for one
       * of these log operations.  Normal reservations have a cnt of 1
       * and their unit amount is the total amount of space required.
       *
       * The following lines of code account for non-transaction data
       * which occupy space in the on-disk log.
       *
       * Normal form of a transaction is:
       * <oph><trans-hdr><start-oph><reg1-oph><reg1><reg2-oph>...<commit-oph>
       * and then there are LR hdrs, split-recs and roundoff at end of syncs.
       *
       * We need to account for all the leadup data and trailer data
       * around the transaction data.
       * And then we need to account for the worst case in terms of using
       * more space.
       * The worst case will happen if:
       * - the placement of the transaction happens to be such that the
       *   roundoff is at its maximum
       * - the transaction data is synced before the commit record is synced
       *   i.e. <transaction-data><roundoff> | <commit-rec><roundoff>
       *   Therefore the commit record is in its own Log Record.
       *   This can happen as the commit record is called with its
       *   own region to xlog_write().
       *   This then means that in the worst case, roundoff can happen for
       *   the commit-rec as well.
       *   The commit-rec is smaller than padding in this scenario and so it is
       *   not added separately.
       */

      /* for trans header */
      unit_bytes += sizeof(xlog_op_header_t);
      unit_bytes += sizeof(xfs_trans_header_t);

      /* for start-rec */
      unit_bytes += sizeof(xlog_op_header_t);

      /* for LR headers */
      num_headers = ((unit_bytes + log->l_iclog_size-1) >> log->l_iclog_size_log);
      unit_bytes += log->l_iclog_hsize * num_headers;

      /* for commit-rec LR header - note: padding will subsume the ophdr */
      unit_bytes += log->l_iclog_hsize;

      /* for split-recs - ophdrs added when data split over LRs */
      unit_bytes += sizeof(xlog_op_header_t) * num_headers;

      /* for roundoff padding for transaction data and one for commit record */
      if (xfs_sb_version_haslogv2(&log->l_mp->m_sb) &&
          log->l_mp->m_sb.sb_logsunit > 1) {
            /* log su roundoff */
            unit_bytes += 2*log->l_mp->m_sb.sb_logsunit;
      } else {
            /* BB roundoff */
            unit_bytes += 2*BBSIZE;
        }

      atomic_set(&tic->t_ref, 1);
      tic->t_unit_res         = unit_bytes;
      tic->t_curr_res         = unit_bytes;
      tic->t_cnt        = cnt;
      tic->t_ocnt       = cnt;
      tic->t_tid        = (xlog_tid_t)((__psint_t)tic & 0xffffffff);
      tic->t_clientid         = client;
      tic->t_flags            = XLOG_TIC_INITED;
      tic->t_trans_type = 0;
      if (xflags & XFS_LOG_PERM_RESERV)
            tic->t_flags |= XLOG_TIC_PERM_RESERV;
      sv_init(&(tic->t_wait), SV_DEFAULT, "logtick");

      xlog_tic_reset_res(tic);

      return tic;
}


/******************************************************************************
 *
 *          Log debug routines
 *
 ******************************************************************************
 */
#if defined(DEBUG)
/*
 * Make sure that the destination ptr is within the valid data region of
 * one of the iclogs.  This uses backup pointers stored in a different
 * part of the log in case we trash the log structure.
 */
void
xlog_verify_dest_ptr(xlog_t     *log,
                 __psint_t  ptr)
{
      int i;
      int good_ptr = 0;

      for (i=0; i < log->l_iclog_bufs; i++) {
            if (ptr >= (__psint_t)log->l_iclog_bak[i] &&
                ptr <= (__psint_t)log->l_iclog_bak[i]+log->l_iclog_size)
                  good_ptr++;
      }
      if (! good_ptr)
            xlog_panic("xlog_verify_dest_ptr: invalid ptr");
}     /* xlog_verify_dest_ptr */

STATIC void
xlog_verify_grant_head(xlog_t *log, int equals)
{
    if (log->l_grant_reserve_cycle == log->l_grant_write_cycle) {
      if (equals)
          ASSERT(log->l_grant_reserve_bytes >= log->l_grant_write_bytes);
      else
          ASSERT(log->l_grant_reserve_bytes > log->l_grant_write_bytes);
    } else {
      ASSERT(log->l_grant_reserve_cycle-1 == log->l_grant_write_cycle);
      ASSERT(log->l_grant_write_bytes >= log->l_grant_reserve_bytes);
    }
}     /* xlog_verify_grant_head */

/* check if it will fit */
STATIC void
xlog_verify_tail_lsn(xlog_t       *log,
                 xlog_in_core_t *iclog,
                 xfs_lsn_t        tail_lsn)
{
    int blocks;

    if (CYCLE_LSN(tail_lsn) == log->l_prev_cycle) {
      blocks =
          log->l_logBBsize - (log->l_prev_block - BLOCK_LSN(tail_lsn));
      if (blocks < BTOBB(iclog->ic_offset)+BTOBB(log->l_iclog_hsize))
          xlog_panic("xlog_verify_tail_lsn: ran out of log space");
    } else {
      ASSERT(CYCLE_LSN(tail_lsn)+1 == log->l_prev_cycle);

      if (BLOCK_LSN(tail_lsn) == log->l_prev_block)
          xlog_panic("xlog_verify_tail_lsn: tail wrapped");

      blocks = BLOCK_LSN(tail_lsn) - log->l_prev_block;
      if (blocks < BTOBB(iclog->ic_offset) + 1)
          xlog_panic("xlog_verify_tail_lsn: ran out of log space");
    }
}     /* xlog_verify_tail_lsn */

/*
 * Perform a number of checks on the iclog before writing to disk.
 *
 * 1. Make sure the iclogs are still circular
 * 2. Make sure we have a good magic number
 * 3. Make sure we don't have magic numbers in the data
 * 4. Check fields of each log operation header for:
 *    A. Valid client identifier
 *    B. tid ptr value falls in valid ptr space (user space code)
 *    C. Length in log record header is correct according to the
 *          individual operation headers within record.
 * 5. When a bwrite will occur within 5 blocks of the front of the physical
 *    log, check the preceding blocks of the physical log to make sure all
 *    the cycle numbers agree with the current cycle number.
 */
STATIC void
xlog_verify_iclog(xlog_t       *log,
              xlog_in_core_t *iclog,
              int        count,
              boolean_t  syncing)
{
      xlog_op_header_t  *ophead;
      xlog_in_core_t          *icptr;
      xlog_in_core_2_t  *xhdr;
      xfs_caddr_t       ptr;
      xfs_caddr_t       base_ptr;
      __psint_t         field_offset;
      __uint8_t         clientid;
      int               len, i, j, k, op_len;
      int               idx;

      /* check validity of iclog pointers */
      spin_lock(&log->l_icloglock);
      icptr = log->l_iclog;
      for (i=0; i < log->l_iclog_bufs; i++) {
            if (icptr == NULL)
                  xlog_panic("xlog_verify_iclog: invalid ptr");
            icptr = icptr->ic_next;
      }
      if (icptr != log->l_iclog)
            xlog_panic("xlog_verify_iclog: corrupt iclog ring");
      spin_unlock(&log->l_icloglock);

      /* check log magic numbers */
      if (be32_to_cpu(iclog->ic_header.h_magicno) != XLOG_HEADER_MAGIC_NUM)
            xlog_panic("xlog_verify_iclog: invalid magic num");

      ptr = (xfs_caddr_t) &iclog->ic_header;
      for (ptr += BBSIZE; ptr < ((xfs_caddr_t)&iclog->ic_header) + count;
           ptr += BBSIZE) {
            if (be32_to_cpu(*(__be32 *)ptr) == XLOG_HEADER_MAGIC_NUM)
                  xlog_panic("xlog_verify_iclog: unexpected magic num");
      }

      /* check fields */
      len = be32_to_cpu(iclog->ic_header.h_num_logops);
      ptr = iclog->ic_datap;
      base_ptr = ptr;
      ophead = (xlog_op_header_t *)ptr;
      xhdr = iclog->ic_data;
      for (i = 0; i < len; i++) {
            ophead = (xlog_op_header_t *)ptr;

            /* clientid is only 1 byte */
            field_offset = (__psint_t)
                         ((xfs_caddr_t)&(ophead->oh_clientid) - base_ptr);
            if (syncing == B_FALSE || (field_offset & 0x1ff)) {
                  clientid = ophead->oh_clientid;
            } else {
                  idx = BTOBBT((xfs_caddr_t)&(ophead->oh_clientid) - iclog->ic_datap);
                  if (idx >= (XLOG_HEADER_CYCLE_SIZE / BBSIZE)) {
                        j = idx / (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        k = idx % (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        clientid = xlog_get_client_id(
                              xhdr[j].hic_xheader.xh_cycle_data[k]);
                  } else {
                        clientid = xlog_get_client_id(
                              iclog->ic_header.h_cycle_data[idx]);
                  }
            }
            if (clientid != XFS_TRANSACTION && clientid != XFS_LOG)
                  cmn_err(CE_WARN, "xlog_verify_iclog: "
                        "invalid clientid %d op 0x%p offset 0x%lx",
                        clientid, ophead, (unsigned long)field_offset);

            /* check length */
            field_offset = (__psint_t)
                         ((xfs_caddr_t)&(ophead->oh_len) - base_ptr);
            if (syncing == B_FALSE || (field_offset & 0x1ff)) {
                  op_len = be32_to_cpu(ophead->oh_len);
            } else {
                  idx = BTOBBT((__psint_t)&ophead->oh_len -
                            (__psint_t)iclog->ic_datap);
                  if (idx >= (XLOG_HEADER_CYCLE_SIZE / BBSIZE)) {
                        j = idx / (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        k = idx % (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        op_len = be32_to_cpu(xhdr[j].hic_xheader.xh_cycle_data[k]);
                  } else {
                        op_len = be32_to_cpu(iclog->ic_header.h_cycle_data[idx]);
                  }
            }
            ptr += sizeof(xlog_op_header_t) + op_len;
      }
}     /* xlog_verify_iclog */
#endif

/*
 * Mark all iclogs IOERROR. l_icloglock is held by the caller.
 */
STATIC int
xlog_state_ioerror(
      xlog_t      *log)
{
      xlog_in_core_t    *iclog, *ic;

      iclog = log->l_iclog;
      if (! (iclog->ic_state & XLOG_STATE_IOERROR)) {
            /*
             * Mark all the incore logs IOERROR.
             * From now on, no log flushes will result.
             */
            ic = iclog;
            do {
                  ic->ic_state = XLOG_STATE_IOERROR;
                  ic = ic->ic_next;
            } while (ic != iclog);
            return 0;
      }
      /*
       * Return non-zero, if state transition has already happened.
       */
      return 1;
}

/*
 * This is called from xfs_force_shutdown, when we're forcibly
 * shutting down the filesystem, typically because of an IO error.
 * Our main objectives here are to make sure that:
 *    a. the filesystem gets marked 'SHUTDOWN' for all interested
 *       parties to find out, 'atomically'.
 *    b. those who're sleeping on log reservations, pinned objects and
 *        other resources get woken up, and be told the bad news.
 *    c. nothing new gets queued up after (a) and (b) are done.
 *    d. if !logerror, flush the iclogs to disk, then seal them off
 *       for business.
 */
int
xfs_log_force_umount(
      struct xfs_mount  *mp,
      int               logerror)
{
      xlog_ticket_t     *tic;
      xlog_t            *log;
      int         retval;
      int         dummy;

      log = mp->m_log;

      /*
       * If this happens during log recovery, don't worry about
       * locking; the log isn't open for business yet.
       */
      if (!log ||
          log->l_flags & XLOG_ACTIVE_RECOVERY) {
            mp->m_flags |= XFS_MOUNT_FS_SHUTDOWN;
            if (mp->m_sb_bp)
                  XFS_BUF_DONE(mp->m_sb_bp);
            return 0;
      }

      /*
       * Somebody could've already done the hard work for us.
       * No need to get locks for this.
       */
      if (logerror && log->l_iclog->ic_state & XLOG_STATE_IOERROR) {
            ASSERT(XLOG_FORCED_SHUTDOWN(log));
            return 1;
      }
      retval = 0;
      /*
       * We must hold both the GRANT lock and the LOG lock,
       * before we mark the filesystem SHUTDOWN and wake
       * everybody up to tell the bad news.
       */
      spin_lock(&log->l_icloglock);
      spin_lock(&log->l_grant_lock);
      mp->m_flags |= XFS_MOUNT_FS_SHUTDOWN;
      if (mp->m_sb_bp)
            XFS_BUF_DONE(mp->m_sb_bp);

      /*
       * This flag is sort of redundant because of the mount flag, but
       * it's good to maintain the separation between the log and the rest
       * of XFS.
       */
      log->l_flags |= XLOG_IO_ERROR;

      /*
       * If we hit a log error, we want to mark all the iclogs IOERROR
       * while we're still holding the loglock.
       */
      if (logerror)
            retval = xlog_state_ioerror(log);
      spin_unlock(&log->l_icloglock);

      /*
       * We don't want anybody waiting for log reservations
       * after this. That means we have to wake up everybody
       * queued up on reserve_headq as well as write_headq.
       * In addition, we make sure in xlog_{re}grant_log_space
       * that we don't enqueue anything once the SHUTDOWN flag
       * is set, and this action is protected by the GRANTLOCK.
       */
      if ((tic = log->l_reserve_headq)) {
            do {
                  sv_signal(&tic->t_wait);
                  tic = tic->t_next;
            } while (tic != log->l_reserve_headq);
      }

      if ((tic = log->l_write_headq)) {
            do {
                  sv_signal(&tic->t_wait);
                  tic = tic->t_next;
            } while (tic != log->l_write_headq);
      }
      spin_unlock(&log->l_grant_lock);

      if (! (log->l_iclog->ic_state & XLOG_STATE_IOERROR)) {
            ASSERT(!logerror);
            /*
             * Force the incore logs to disk before shutting the
             * log down completely.
             */
            xlog_state_sync_all(log, XFS_LOG_FORCE|XFS_LOG_SYNC, &dummy);
            spin_lock(&log->l_icloglock);
            retval = xlog_state_ioerror(log);
            spin_unlock(&log->l_icloglock);
      }
      /*
       * Wake up everybody waiting on xfs_log_force.
       * Callback all log item committed functions as if the
       * log writes were completed.
       */
      xlog_state_do_callback(log, XFS_LI_ABORTED, NULL);

#ifdef XFSERRORDEBUG
      {
            xlog_in_core_t    *iclog;

            spin_lock(&log->l_icloglock);
            iclog = log->l_iclog;
            do {
                  ASSERT(iclog->ic_callback == 0);
                  iclog = iclog->ic_next;
            } while (iclog != log->l_iclog);
            spin_unlock(&log->l_icloglock);
      }
#endif
      /* return non-zero if log IOERROR transition had already happened */
      return retval;
}

STATIC int
xlog_iclogs_empty(xlog_t *log)
{
      xlog_in_core_t    *iclog;

      iclog = log->l_iclog;
      do {
            /* endianness does not matter here, zero is zero in
             * any language.
             */
            if (iclog->ic_header.h_num_logops)
                  return 0;
            iclog = iclog->ic_next;
      } while (iclog != log->l_iclog);
      return 1;
}

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