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xfs_buf_item.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_dmapi.h"
#include "xfs_mount.h"
#include "xfs_buf_item.h"
#include "xfs_trans_priv.h"
#include "xfs_error.h"


kmem_zone_t *xfs_buf_item_zone;

#ifdef XFS_TRANS_DEBUG
/*
 * This function uses an alternate strategy for tracking the bytes
 * that the user requests to be logged.  This can then be used
 * in conjunction with the bli_orig array in the buf log item to
 * catch bugs in our callers' code.
 *
 * We also double check the bits set in xfs_buf_item_log using a
 * simple algorithm to check that every byte is accounted for.
 */
STATIC void
xfs_buf_item_log_debug(
      xfs_buf_log_item_t      *bip,
      uint              first,
      uint              last)
{
      uint  x;
      uint  byte;
      uint  nbytes;
      uint  chunk_num;
      uint  word_num;
      uint  bit_num;
      uint  bit_set;
      uint  *wordp;

      ASSERT(bip->bli_logged != NULL);
      byte = first;
      nbytes = last - first + 1;
      bfset(bip->bli_logged, first, nbytes);
      for (x = 0; x < nbytes; x++) {
            chunk_num = byte >> XFS_BLI_SHIFT;
            word_num = chunk_num >> BIT_TO_WORD_SHIFT;
            bit_num = chunk_num & (NBWORD - 1);
            wordp = &(bip->bli_format.blf_data_map[word_num]);
            bit_set = *wordp & (1 << bit_num);
            ASSERT(bit_set);
            byte++;
      }
}

/*
 * This function is called when we flush something into a buffer without
 * logging it.  This happens for things like inodes which are logged
 * separately from the buffer.
 */
void
xfs_buf_item_flush_log_debug(
      xfs_buf_t   *bp,
      uint        first,
      uint        last)
{
      xfs_buf_log_item_t      *bip;
      uint              nbytes;

      bip = XFS_BUF_FSPRIVATE(bp, xfs_buf_log_item_t*);
      if ((bip == NULL) || (bip->bli_item.li_type != XFS_LI_BUF)) {
            return;
      }

      ASSERT(bip->bli_logged != NULL);
      nbytes = last - first + 1;
      bfset(bip->bli_logged, first, nbytes);
}

/*
 * This function is called to verify that our callers have logged
 * all the bytes that they changed.
 *
 * It does this by comparing the original copy of the buffer stored in
 * the buf log item's bli_orig array to the current copy of the buffer
 * and ensuring that all bytes which mismatch are set in the bli_logged
 * array of the buf log item.
 */
STATIC void
xfs_buf_item_log_check(
      xfs_buf_log_item_t      *bip)
{
      char        *orig;
      char        *buffer;
      int         x;
      xfs_buf_t   *bp;

      ASSERT(bip->bli_orig != NULL);
      ASSERT(bip->bli_logged != NULL);

      bp = bip->bli_buf;
      ASSERT(XFS_BUF_COUNT(bp) > 0);
      ASSERT(XFS_BUF_PTR(bp) != NULL);
      orig = bip->bli_orig;
      buffer = XFS_BUF_PTR(bp);
      for (x = 0; x < XFS_BUF_COUNT(bp); x++) {
            if (orig[x] != buffer[x] && !btst(bip->bli_logged, x))
                  cmn_err(CE_PANIC,
      "xfs_buf_item_log_check bip %x buffer %x orig %x index %d",
                        bip, bp, orig, x);
      }
}
#else
#define           xfs_buf_item_log_debug(x,y,z)
#define           xfs_buf_item_log_check(x)
#endif

STATIC void xfs_buf_error_relse(xfs_buf_t *bp);
STATIC void xfs_buf_do_callbacks(xfs_buf_t *bp, xfs_log_item_t *lip);

/*
 * This returns the number of log iovecs needed to log the
 * given buf log item.
 *
 * It calculates this as 1 iovec for the buf log format structure
 * and 1 for each stretch of non-contiguous chunks to be logged.
 * Contiguous chunks are logged in a single iovec.
 *
 * If the XFS_BLI_STALE flag has been set, then log nothing.
 */
STATIC uint
xfs_buf_item_size(
      xfs_buf_log_item_t      *bip)
{
      uint        nvecs;
      int         next_bit;
      int         last_bit;
      xfs_buf_t   *bp;

      ASSERT(atomic_read(&bip->bli_refcount) > 0);
      if (bip->bli_flags & XFS_BLI_STALE) {
            /*
             * The buffer is stale, so all we need to log
             * is the buf log format structure with the
             * cancel flag in it.
             */
            xfs_buf_item_trace("SIZE STALE", bip);
            ASSERT(bip->bli_format.blf_flags & XFS_BLI_CANCEL);
            return 1;
      }

      bp = bip->bli_buf;
      ASSERT(bip->bli_flags & XFS_BLI_LOGGED);
      nvecs = 1;
      last_bit = xfs_next_bit(bip->bli_format.blf_data_map,
                               bip->bli_format.blf_map_size, 0);
      ASSERT(last_bit != -1);
      nvecs++;
      while (last_bit != -1) {
            /*
             * This takes the bit number to start looking from and
             * returns the next set bit from there.  It returns -1
             * if there are no more bits set or the start bit is
             * beyond the end of the bitmap.
             */
            next_bit = xfs_next_bit(bip->bli_format.blf_data_map,
                                     bip->bli_format.blf_map_size,
                                     last_bit + 1);
            /*
             * If we run out of bits, leave the loop,
             * else if we find a new set of bits bump the number of vecs,
             * else keep scanning the current set of bits.
             */
            if (next_bit == -1) {
                  last_bit = -1;
            } else if (next_bit != last_bit + 1) {
                  last_bit = next_bit;
                  nvecs++;
            } else if (xfs_buf_offset(bp, next_bit * XFS_BLI_CHUNK) !=
                     (xfs_buf_offset(bp, last_bit * XFS_BLI_CHUNK) +
                      XFS_BLI_CHUNK)) {
                  last_bit = next_bit;
                  nvecs++;
            } else {
                  last_bit++;
            }
      }

      xfs_buf_item_trace("SIZE NORM", bip);
      return nvecs;
}

/*
 * This is called to fill in the vector of log iovecs for the
 * given log buf item.  It fills the first entry with a buf log
 * format structure, and the rest point to contiguous chunks
 * within the buffer.
 */
STATIC void
xfs_buf_item_format(
      xfs_buf_log_item_t      *bip,
      xfs_log_iovec_t         *log_vector)
{
      uint        base_size;
      uint        nvecs;
      xfs_log_iovec_t   *vecp;
      xfs_buf_t   *bp;
      int         first_bit;
      int         last_bit;
      int         next_bit;
      uint        nbits;
      uint        buffer_offset;

      ASSERT(atomic_read(&bip->bli_refcount) > 0);
      ASSERT((bip->bli_flags & XFS_BLI_LOGGED) ||
             (bip->bli_flags & XFS_BLI_STALE));
      bp = bip->bli_buf;
      vecp = log_vector;

      /*
       * The size of the base structure is the size of the
       * declared structure plus the space for the extra words
       * of the bitmap.  We subtract one from the map size, because
       * the first element of the bitmap is accounted for in the
       * size of the base structure.
       */
      base_size =
            (uint)(sizeof(xfs_buf_log_format_t) +
                   ((bip->bli_format.blf_map_size - 1) * sizeof(uint)));
      vecp->i_addr = (xfs_caddr_t)&bip->bli_format;
      vecp->i_len = base_size;
      XLOG_VEC_SET_TYPE(vecp, XLOG_REG_TYPE_BFORMAT);
      vecp++;
      nvecs = 1;

      if (bip->bli_flags & XFS_BLI_STALE) {
            /*
             * The buffer is stale, so all we need to log
             * is the buf log format structure with the
             * cancel flag in it.
             */
            xfs_buf_item_trace("FORMAT STALE", bip);
            ASSERT(bip->bli_format.blf_flags & XFS_BLI_CANCEL);
            bip->bli_format.blf_size = nvecs;
            return;
      }

      /*
       * Fill in an iovec for each set of contiguous chunks.
       */
      first_bit = xfs_next_bit(bip->bli_format.blf_data_map,
                               bip->bli_format.blf_map_size, 0);
      ASSERT(first_bit != -1);
      last_bit = first_bit;
      nbits = 1;
      for (;;) {
            /*
             * This takes the bit number to start looking from and
             * returns the next set bit from there.  It returns -1
             * if there are no more bits set or the start bit is
             * beyond the end of the bitmap.
             */
            next_bit = xfs_next_bit(bip->bli_format.blf_data_map,
                                     bip->bli_format.blf_map_size,
                                     (uint)last_bit + 1);
            /*
             * If we run out of bits fill in the last iovec and get
             * out of the loop.
             * Else if we start a new set of bits then fill in the
             * iovec for the series we were looking at and start
             * counting the bits in the new one.
             * Else we're still in the same set of bits so just
             * keep counting and scanning.
             */
            if (next_bit == -1) {
                  buffer_offset = first_bit * XFS_BLI_CHUNK;
                  vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
                  vecp->i_len = nbits * XFS_BLI_CHUNK;
                  XLOG_VEC_SET_TYPE(vecp, XLOG_REG_TYPE_BCHUNK);
                  nvecs++;
                  break;
            } else if (next_bit != last_bit + 1) {
                  buffer_offset = first_bit * XFS_BLI_CHUNK;
                  vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
                  vecp->i_len = nbits * XFS_BLI_CHUNK;
                  XLOG_VEC_SET_TYPE(vecp, XLOG_REG_TYPE_BCHUNK);
                  nvecs++;
                  vecp++;
                  first_bit = next_bit;
                  last_bit = next_bit;
                  nbits = 1;
            } else if (xfs_buf_offset(bp, next_bit << XFS_BLI_SHIFT) !=
                     (xfs_buf_offset(bp, last_bit << XFS_BLI_SHIFT) +
                      XFS_BLI_CHUNK)) {
                  buffer_offset = first_bit * XFS_BLI_CHUNK;
                  vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
                  vecp->i_len = nbits * XFS_BLI_CHUNK;
                  XLOG_VEC_SET_TYPE(vecp, XLOG_REG_TYPE_BCHUNK);
/* You would think we need to bump the nvecs here too, but we do not
 * this number is used by recovery, and it gets confused by the boundary
 * split here
 *                nvecs++;
 */
                  vecp++;
                  first_bit = next_bit;
                  last_bit = next_bit;
                  nbits = 1;
            } else {
                  last_bit++;
                  nbits++;
            }
      }
      bip->bli_format.blf_size = nvecs;

      /*
       * Check to make sure everything is consistent.
       */
      xfs_buf_item_trace("FORMAT NORM", bip);
      xfs_buf_item_log_check(bip);
}

/*
 * This is called to pin the buffer associated with the buf log
 * item in memory so it cannot be written out.  Simply call bpin()
 * on the buffer to do this.
 */
STATIC void
xfs_buf_item_pin(
      xfs_buf_log_item_t      *bip)
{
      xfs_buf_t   *bp;

      bp = bip->bli_buf;
      ASSERT(XFS_BUF_ISBUSY(bp));
      ASSERT(atomic_read(&bip->bli_refcount) > 0);
      ASSERT((bip->bli_flags & XFS_BLI_LOGGED) ||
             (bip->bli_flags & XFS_BLI_STALE));
      xfs_buf_item_trace("PIN", bip);
      xfs_buftrace("XFS_PIN", bp);
      xfs_bpin(bp);
}


/*
 * This is called to unpin the buffer associated with the buf log
 * item which was previously pinned with a call to xfs_buf_item_pin().
 * Just call bunpin() on the buffer to do this.
 *
 * Also drop the reference to the buf item for the current transaction.
 * If the XFS_BLI_STALE flag is set and we are the last reference,
 * then free up the buf log item and unlock the buffer.
 */
STATIC void
xfs_buf_item_unpin(
      xfs_buf_log_item_t      *bip,
      int               stale)
{
      xfs_mount_t *mp;
      xfs_buf_t   *bp;
      int         freed;
      SPLDECL(s);

      bp = bip->bli_buf;
      ASSERT(bp != NULL);
      ASSERT(XFS_BUF_FSPRIVATE(bp, xfs_buf_log_item_t *) == bip);
      ASSERT(atomic_read(&bip->bli_refcount) > 0);
      xfs_buf_item_trace("UNPIN", bip);
      xfs_buftrace("XFS_UNPIN", bp);

      freed = atomic_dec_and_test(&bip->bli_refcount);
      mp = bip->bli_item.li_mountp;
      xfs_bunpin(bp);
      if (freed && stale) {
            ASSERT(bip->bli_flags & XFS_BLI_STALE);
            ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);
            ASSERT(!(XFS_BUF_ISDELAYWRITE(bp)));
            ASSERT(XFS_BUF_ISSTALE(bp));
            ASSERT(bip->bli_format.blf_flags & XFS_BLI_CANCEL);
            xfs_buf_item_trace("UNPIN STALE", bip);
            xfs_buftrace("XFS_UNPIN STALE", bp);
            /*
             * If we get called here because of an IO error, we may
             * or may not have the item on the AIL. xfs_trans_delete_ail()
             * will take care of that situation.
             * xfs_trans_delete_ail() drops the AIL lock.
             */
            if (bip->bli_flags & XFS_BLI_STALE_INODE) {
                  xfs_buf_do_callbacks(bp, (xfs_log_item_t *)bip);
                  XFS_BUF_SET_FSPRIVATE(bp, NULL);
                  XFS_BUF_CLR_IODONE_FUNC(bp);
            } else {
                  AIL_LOCK(mp,s);
                  xfs_trans_delete_ail(mp, (xfs_log_item_t *)bip, s);
                  xfs_buf_item_relse(bp);
                  ASSERT(XFS_BUF_FSPRIVATE(bp, void *) == NULL);
            }
            xfs_buf_relse(bp);
      }
}

/*
 * this is called from uncommit in the forced-shutdown path.
 * we need to check to see if the reference count on the log item
 * is going to drop to zero.  If so, unpin will free the log item
 * so we need to free the item's descriptor (that points to the item)
 * in the transaction.
 */
STATIC void
xfs_buf_item_unpin_remove(
      xfs_buf_log_item_t      *bip,
      xfs_trans_t       *tp)
{
      xfs_buf_t         *bp;
      xfs_log_item_desc_t     *lidp;
      int               stale = 0;

      bp = bip->bli_buf;
      /*
       * will xfs_buf_item_unpin() call xfs_buf_item_relse()?
       */
      if ((atomic_read(&bip->bli_refcount) == 1) &&
          (bip->bli_flags & XFS_BLI_STALE)) {
            ASSERT(XFS_BUF_VALUSEMA(bip->bli_buf) <= 0);
            xfs_buf_item_trace("UNPIN REMOVE", bip);
            xfs_buftrace("XFS_UNPIN_REMOVE", bp);
            /*
             * yes -- clear the xaction descriptor in-use flag
             * and free the chunk if required.  We can safely
             * do some work here and then call buf_item_unpin
             * to do the rest because if the if is true, then
             * we are holding the buffer locked so no one else
             * will be able to bump up the refcount.
             */
            lidp = xfs_trans_find_item(tp, (xfs_log_item_t *) bip);
            stale = lidp->lid_flags & XFS_LID_BUF_STALE;
            xfs_trans_free_item(tp, lidp);
            /*
             * Since the transaction no longer refers to the buffer,
             * the buffer should no longer refer to the transaction.
             */
            XFS_BUF_SET_FSPRIVATE2(bp, NULL);
      }

      xfs_buf_item_unpin(bip, stale);

      return;
}

/*
 * This is called to attempt to lock the buffer associated with this
 * buf log item.  Don't sleep on the buffer lock.  If we can't get
 * the lock right away, return 0.  If we can get the lock, pull the
 * buffer from the free list, mark it busy, and return 1.
 */
STATIC uint
xfs_buf_item_trylock(
      xfs_buf_log_item_t      *bip)
{
      xfs_buf_t   *bp;

      bp = bip->bli_buf;

      if (XFS_BUF_ISPINNED(bp)) {
            return XFS_ITEM_PINNED;
      }

      if (!XFS_BUF_CPSEMA(bp)) {
            return XFS_ITEM_LOCKED;
      }

      /*
       * Remove the buffer from the free list.  Only do this
       * if it's on the free list.  Private buffers like the
       * superblock buffer are not.
       */
      XFS_BUF_HOLD(bp);

      ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
      xfs_buf_item_trace("TRYLOCK SUCCESS", bip);
      return XFS_ITEM_SUCCESS;
}

/*
 * Release the buffer associated with the buf log item.
 * If there is no dirty logged data associated with the
 * buffer recorded in the buf log item, then free the
 * buf log item and remove the reference to it in the
 * buffer.
 *
 * This call ignores the recursion count.  It is only called
 * when the buffer should REALLY be unlocked, regardless
 * of the recursion count.
 *
 * If the XFS_BLI_HOLD flag is set in the buf log item, then
 * free the log item if necessary but do not unlock the buffer.
 * This is for support of xfs_trans_bhold(). Make sure the
 * XFS_BLI_HOLD field is cleared if we don't free the item.
 */
STATIC void
xfs_buf_item_unlock(
      xfs_buf_log_item_t      *bip)
{
      int         aborted;
      xfs_buf_t   *bp;
      uint        hold;

      bp = bip->bli_buf;
      xfs_buftrace("XFS_UNLOCK", bp);

      /*
       * Clear the buffer's association with this transaction.
       */
      XFS_BUF_SET_FSPRIVATE2(bp, NULL);

      /*
       * If this is a transaction abort, don't return early.
       * Instead, allow the brelse to happen.
       * Normally it would be done for stale (cancelled) buffers
       * at unpin time, but we'll never go through the pin/unpin
       * cycle if we abort inside commit.
       */
      aborted = (bip->bli_item.li_flags & XFS_LI_ABORTED) != 0;

      /*
       * If the buf item is marked stale, then don't do anything.
       * We'll unlock the buffer and free the buf item when the
       * buffer is unpinned for the last time.
       */
      if (bip->bli_flags & XFS_BLI_STALE) {
            bip->bli_flags &= ~XFS_BLI_LOGGED;
            xfs_buf_item_trace("UNLOCK STALE", bip);
            ASSERT(bip->bli_format.blf_flags & XFS_BLI_CANCEL);
            if (!aborted)
                  return;
      }

      /*
       * Drop the transaction's reference to the log item if
       * it was not logged as part of the transaction.  Otherwise
       * we'll drop the reference in xfs_buf_item_unpin() when
       * the transaction is really through with the buffer.
       */
      if (!(bip->bli_flags & XFS_BLI_LOGGED)) {
            atomic_dec(&bip->bli_refcount);
      } else {
            /*
             * Clear the logged flag since this is per
             * transaction state.
             */
            bip->bli_flags &= ~XFS_BLI_LOGGED;
      }

      /*
       * Before possibly freeing the buf item, determine if we should
       * release the buffer at the end of this routine.
       */
      hold = bip->bli_flags & XFS_BLI_HOLD;
      xfs_buf_item_trace("UNLOCK", bip);

      /*
       * If the buf item isn't tracking any data, free it.
       * Otherwise, if XFS_BLI_HOLD is set clear it.
       */
      if (xfs_bitmap_empty(bip->bli_format.blf_data_map,
                       bip->bli_format.blf_map_size)) {
            xfs_buf_item_relse(bp);
      } else if (hold) {
            bip->bli_flags &= ~XFS_BLI_HOLD;
      }

      /*
       * Release the buffer if XFS_BLI_HOLD was not set.
       */
      if (!hold) {
            xfs_buf_relse(bp);
      }
}

/*
 * This is called to find out where the oldest active copy of the
 * buf log item in the on disk log resides now that the last log
 * write of it completed at the given lsn.
 * We always re-log all the dirty data in a buffer, so usually the
 * latest copy in the on disk log is the only one that matters.  For
 * those cases we simply return the given lsn.
 *
 * The one exception to this is for buffers full of newly allocated
 * inodes.  These buffers are only relogged with the XFS_BLI_INODE_BUF
 * flag set, indicating that only the di_next_unlinked fields from the
 * inodes in the buffers will be replayed during recovery.  If the
 * original newly allocated inode images have not yet been flushed
 * when the buffer is so relogged, then we need to make sure that we
 * keep the old images in the 'active' portion of the log.  We do this
 * by returning the original lsn of that transaction here rather than
 * the current one.
 */
STATIC xfs_lsn_t
xfs_buf_item_committed(
      xfs_buf_log_item_t      *bip,
      xfs_lsn_t         lsn)
{
      xfs_buf_item_trace("COMMITTED", bip);
      if ((bip->bli_flags & XFS_BLI_INODE_ALLOC_BUF) &&
          (bip->bli_item.li_lsn != 0)) {
            return bip->bli_item.li_lsn;
      }
      return (lsn);
}

/*
 * This is called to asynchronously write the buffer associated with this
 * buf log item out to disk. The buffer will already have been locked by
 * a successful call to xfs_buf_item_trylock().  If the buffer still has
 * B_DELWRI set, then get it going out to disk with a call to bawrite().
 * If not, then just release the buffer.
 */
STATIC void
xfs_buf_item_push(
      xfs_buf_log_item_t      *bip)
{
      xfs_buf_t   *bp;

      ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
      xfs_buf_item_trace("PUSH", bip);

      bp = bip->bli_buf;

      if (XFS_BUF_ISDELAYWRITE(bp)) {
            xfs_bawrite(bip->bli_item.li_mountp, bp);
      } else {
            xfs_buf_relse(bp);
      }
}

/* ARGSUSED */
STATIC void
xfs_buf_item_committing(xfs_buf_log_item_t *bip, xfs_lsn_t commit_lsn)
{
}

/*
 * This is the ops vector shared by all buf log items.
 */
static struct xfs_item_ops xfs_buf_item_ops = {
      .iop_size   = (uint(*)(xfs_log_item_t*))xfs_buf_item_size,
      .iop_format = (void(*)(xfs_log_item_t*, xfs_log_iovec_t*))
                              xfs_buf_item_format,
      .iop_pin    = (void(*)(xfs_log_item_t*))xfs_buf_item_pin,
      .iop_unpin  = (void(*)(xfs_log_item_t*, int))xfs_buf_item_unpin,
      .iop_unpin_remove = (void(*)(xfs_log_item_t*, xfs_trans_t *))
                              xfs_buf_item_unpin_remove,
      .iop_trylock      = (uint(*)(xfs_log_item_t*))xfs_buf_item_trylock,
      .iop_unlock = (void(*)(xfs_log_item_t*))xfs_buf_item_unlock,
      .iop_committed    = (xfs_lsn_t(*)(xfs_log_item_t*, xfs_lsn_t))
                              xfs_buf_item_committed,
      .iop_push   = (void(*)(xfs_log_item_t*))xfs_buf_item_push,
      .iop_pushbuf      = NULL,
      .iop_committing = (void(*)(xfs_log_item_t*, xfs_lsn_t))
                              xfs_buf_item_committing
};


/*
 * Allocate a new buf log item to go with the given buffer.
 * Set the buffer's b_fsprivate field to point to the new
 * buf log item.  If there are other item's attached to the
 * buffer (see xfs_buf_attach_iodone() below), then put the
 * buf log item at the front.
 */
void
xfs_buf_item_init(
      xfs_buf_t   *bp,
      xfs_mount_t *mp)
{
      xfs_log_item_t          *lip;
      xfs_buf_log_item_t      *bip;
      int               chunks;
      int               map_size;

      /*
       * Check to see if there is already a buf log item for
       * this buffer.  If there is, it is guaranteed to be
       * the first.  If we do already have one, there is
       * nothing to do here so return.
       */
      if (XFS_BUF_FSPRIVATE3(bp, xfs_mount_t *) != mp)
            XFS_BUF_SET_FSPRIVATE3(bp, mp);
      XFS_BUF_SET_BDSTRAT_FUNC(bp, xfs_bdstrat_cb);
      if (XFS_BUF_FSPRIVATE(bp, void *) != NULL) {
            lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
            if (lip->li_type == XFS_LI_BUF) {
                  return;
            }
      }

      /*
       * chunks is the number of XFS_BLI_CHUNK size pieces
       * the buffer can be divided into. Make sure not to
       * truncate any pieces.  map_size is the size of the
       * bitmap needed to describe the chunks of the buffer.
       */
      chunks = (int)((XFS_BUF_COUNT(bp) + (XFS_BLI_CHUNK - 1)) >> XFS_BLI_SHIFT);
      map_size = (int)((chunks + NBWORD) >> BIT_TO_WORD_SHIFT);

      bip = (xfs_buf_log_item_t*)kmem_zone_zalloc(xfs_buf_item_zone,
                                        KM_SLEEP);
      bip->bli_item.li_type = XFS_LI_BUF;
      bip->bli_item.li_ops = &xfs_buf_item_ops;
      bip->bli_item.li_mountp = mp;
      bip->bli_buf = bp;
      bip->bli_format.blf_type = XFS_LI_BUF;
      bip->bli_format.blf_blkno = (__int64_t)XFS_BUF_ADDR(bp);
      bip->bli_format.blf_len = (ushort)BTOBB(XFS_BUF_COUNT(bp));
      bip->bli_format.blf_map_size = map_size;
#ifdef XFS_BLI_TRACE
      bip->bli_trace = ktrace_alloc(XFS_BLI_TRACE_SIZE, KM_SLEEP);
#endif

#ifdef XFS_TRANS_DEBUG
      /*
       * Allocate the arrays for tracking what needs to be logged
       * and what our callers request to be logged.  bli_orig
       * holds a copy of the original, clean buffer for comparison
       * against, and bli_logged keeps a 1 bit flag per byte in
       * the buffer to indicate which bytes the callers have asked
       * to have logged.
       */
      bip->bli_orig = (char *)kmem_alloc(XFS_BUF_COUNT(bp), KM_SLEEP);
      memcpy(bip->bli_orig, XFS_BUF_PTR(bp), XFS_BUF_COUNT(bp));
      bip->bli_logged = (char *)kmem_zalloc(XFS_BUF_COUNT(bp) / NBBY, KM_SLEEP);
#endif

      /*
       * Put the buf item into the list of items attached to the
       * buffer at the front.
       */
      if (XFS_BUF_FSPRIVATE(bp, void *) != NULL) {
            bip->bli_item.li_bio_list =
                        XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
      }
      XFS_BUF_SET_FSPRIVATE(bp, bip);
}


/*
 * Mark bytes first through last inclusive as dirty in the buf
 * item's bitmap.
 */
void
xfs_buf_item_log(
      xfs_buf_log_item_t      *bip,
      uint              first,
      uint              last)
{
      uint        first_bit;
      uint        last_bit;
      uint        bits_to_set;
      uint        bits_set;
      uint        word_num;
      uint        *wordp;
      uint        bit;
      uint        end_bit;
      uint        mask;

      /*
       * Mark the item as having some dirty data for
       * quick reference in xfs_buf_item_dirty.
       */
      bip->bli_flags |= XFS_BLI_DIRTY;

      /*
       * Convert byte offsets to bit numbers.
       */
      first_bit = first >> XFS_BLI_SHIFT;
      last_bit = last >> XFS_BLI_SHIFT;

      /*
       * Calculate the total number of bits to be set.
       */
      bits_to_set = last_bit - first_bit + 1;

      /*
       * Get a pointer to the first word in the bitmap
       * to set a bit in.
       */
      word_num = first_bit >> BIT_TO_WORD_SHIFT;
      wordp = &(bip->bli_format.blf_data_map[word_num]);

      /*
       * Calculate the starting bit in the first word.
       */
      bit = first_bit & (uint)(NBWORD - 1);

      /*
       * First set any bits in the first word of our range.
       * If it starts at bit 0 of the word, it will be
       * set below rather than here.  That is what the variable
       * bit tells us. The variable bits_set tracks the number
       * of bits that have been set so far.  End_bit is the number
       * of the last bit to be set in this word plus one.
       */
      if (bit) {
            end_bit = MIN(bit + bits_to_set, (uint)NBWORD);
            mask = ((1 << (end_bit - bit)) - 1) << bit;
            *wordp |= mask;
            wordp++;
            bits_set = end_bit - bit;
      } else {
            bits_set = 0;
      }

      /*
       * Now set bits a whole word at a time that are between
       * first_bit and last_bit.
       */
      while ((bits_to_set - bits_set) >= NBWORD) {
            *wordp |= 0xffffffff;
            bits_set += NBWORD;
            wordp++;
      }

      /*
       * Finally, set any bits left to be set in one last partial word.
       */
      end_bit = bits_to_set - bits_set;
      if (end_bit) {
            mask = (1 << end_bit) - 1;
            *wordp |= mask;
      }

      xfs_buf_item_log_debug(bip, first, last);
}


/*
 * Return 1 if the buffer has some data that has been logged (at any
 * point, not just the current transaction) and 0 if not.
 */
uint
xfs_buf_item_dirty(
      xfs_buf_log_item_t      *bip)
{
      return (bip->bli_flags & XFS_BLI_DIRTY);
}

/*
 * This is called when the buf log item is no longer needed.  It should
 * free the buf log item associated with the given buffer and clear
 * the buffer's pointer to the buf log item.  If there are no more
 * items in the list, clear the b_iodone field of the buffer (see
 * xfs_buf_attach_iodone() below).
 */
void
xfs_buf_item_relse(
      xfs_buf_t   *bp)
{
      xfs_buf_log_item_t      *bip;

      xfs_buftrace("XFS_RELSE", bp);
      bip = XFS_BUF_FSPRIVATE(bp, xfs_buf_log_item_t*);
      XFS_BUF_SET_FSPRIVATE(bp, bip->bli_item.li_bio_list);
      if ((XFS_BUF_FSPRIVATE(bp, void *) == NULL) &&
          (XFS_BUF_IODONE_FUNC(bp) != NULL)) {
            XFS_BUF_CLR_IODONE_FUNC(bp);
      }

#ifdef XFS_TRANS_DEBUG
      kmem_free(bip->bli_orig, XFS_BUF_COUNT(bp));
      bip->bli_orig = NULL;
      kmem_free(bip->bli_logged, XFS_BUF_COUNT(bp) / NBBY);
      bip->bli_logged = NULL;
#endif /* XFS_TRANS_DEBUG */

#ifdef XFS_BLI_TRACE
      ktrace_free(bip->bli_trace);
#endif
      kmem_zone_free(xfs_buf_item_zone, bip);
}


/*
 * Add the given log item with its callback to the list of callbacks
 * to be called when the buffer's I/O completes.  If it is not set
 * already, set the buffer's b_iodone() routine to be
 * xfs_buf_iodone_callbacks() and link the log item into the list of
 * items rooted at b_fsprivate.  Items are always added as the second
 * entry in the list if there is a first, because the buf item code
 * assumes that the buf log item is first.
 */
void
xfs_buf_attach_iodone(
      xfs_buf_t   *bp,
      void        (*cb)(xfs_buf_t *, xfs_log_item_t *),
      xfs_log_item_t    *lip)
{
      xfs_log_item_t    *head_lip;

      ASSERT(XFS_BUF_ISBUSY(bp));
      ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);

      lip->li_cb = cb;
      if (XFS_BUF_FSPRIVATE(bp, void *) != NULL) {
            head_lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
            lip->li_bio_list = head_lip->li_bio_list;
            head_lip->li_bio_list = lip;
      } else {
            XFS_BUF_SET_FSPRIVATE(bp, lip);
      }

      ASSERT((XFS_BUF_IODONE_FUNC(bp) == xfs_buf_iodone_callbacks) ||
             (XFS_BUF_IODONE_FUNC(bp) == NULL));
      XFS_BUF_SET_IODONE_FUNC(bp, xfs_buf_iodone_callbacks);
}

STATIC void
xfs_buf_do_callbacks(
      xfs_buf_t   *bp,
      xfs_log_item_t    *lip)
{
      xfs_log_item_t    *nlip;

      while (lip != NULL) {
            nlip = lip->li_bio_list;
            ASSERT(lip->li_cb != NULL);
            /*
             * Clear the next pointer so we don't have any
             * confusion if the item is added to another buf.
             * Don't touch the log item after calling its
             * callback, because it could have freed itself.
             */
            lip->li_bio_list = NULL;
            lip->li_cb(bp, lip);
            lip = nlip;
      }
}

/*
 * This is the iodone() function for buffers which have had callbacks
 * attached to them by xfs_buf_attach_iodone().  It should remove each
 * log item from the buffer's list and call the callback of each in turn.
 * When done, the buffer's fsprivate field is set to NULL and the buffer
 * is unlocked with a call to iodone().
 */
void
xfs_buf_iodone_callbacks(
      xfs_buf_t   *bp)
{
      xfs_log_item_t    *lip;
      static ulong      lasttime;
      static xfs_buftarg_t *lasttarg;
      xfs_mount_t *mp;

      ASSERT(XFS_BUF_FSPRIVATE(bp, void *) != NULL);
      lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);

      if (XFS_BUF_GETERROR(bp) != 0) {
            /*
             * If we've already decided to shutdown the filesystem
             * because of IO errors, there's no point in giving this
             * a retry.
             */
            mp = lip->li_mountp;
            if (XFS_FORCED_SHUTDOWN(mp)) {
                  ASSERT(XFS_BUF_TARGET(bp) == mp->m_ddev_targp);
                  XFS_BUF_SUPER_STALE(bp);
                  xfs_buftrace("BUF_IODONE_CB", bp);
                  xfs_buf_do_callbacks(bp, lip);
                  XFS_BUF_SET_FSPRIVATE(bp, NULL);
                  XFS_BUF_CLR_IODONE_FUNC(bp);

                  /*
                   * XFS_SHUT flag gets set when we go thru the
                   * entire buffer cache and deliberately start
                   * throwing away delayed write buffers.
                   * Since there's no biowait done on those,
                   * we should just brelse them.
                   */
                  if (XFS_BUF_ISSHUT(bp)) {
                      XFS_BUF_UNSHUT(bp);
                        xfs_buf_relse(bp);
                  } else {
                        xfs_biodone(bp);
                  }

                  return;
            }

            if ((XFS_BUF_TARGET(bp) != lasttarg) ||
                (time_after(jiffies, (lasttime + 5*HZ)))) {
                  lasttime = jiffies;
                  cmn_err(CE_ALERT, "Device %s, XFS metadata write error"
                              " block 0x%llx in %s",
                        XFS_BUFTARG_NAME(XFS_BUF_TARGET(bp)),
                        (__uint64_t)XFS_BUF_ADDR(bp), mp->m_fsname);
            }
            lasttarg = XFS_BUF_TARGET(bp);

            if (XFS_BUF_ISASYNC(bp)) {
                  /*
                   * If the write was asynchronous then noone will be
                   * looking for the error.  Clear the error state
                   * and write the buffer out again delayed write.
                   *
                   * XXXsup This is OK, so long as we catch these
                   * before we start the umount; we don't want these
                   * DELWRI metadata bufs to be hanging around.
                   */
                  XFS_BUF_ERROR(bp,0); /* errno of 0 unsets the flag */

                  if (!(XFS_BUF_ISSTALE(bp))) {
                        XFS_BUF_DELAYWRITE(bp);
                        XFS_BUF_DONE(bp);
                        XFS_BUF_SET_START(bp);
                  }
                  ASSERT(XFS_BUF_IODONE_FUNC(bp));
                  xfs_buftrace("BUF_IODONE ASYNC", bp);
                  xfs_buf_relse(bp);
            } else {
                  /*
                   * If the write of the buffer was not asynchronous,
                   * then we want to make sure to return the error
                   * to the caller of bwrite().  Because of this we
                   * cannot clear the B_ERROR state at this point.
                   * Instead we install a callback function that
                   * will be called when the buffer is released, and
                   * that routine will clear the error state and
                   * set the buffer to be written out again after
                   * some delay.
                   */
                  /* We actually overwrite the existing b-relse
                     function at times, but we're gonna be shutting down
                     anyway. */
                  XFS_BUF_SET_BRELSE_FUNC(bp,xfs_buf_error_relse);
                  XFS_BUF_DONE(bp);
                  XFS_BUF_V_IODONESEMA(bp);
            }
            return;
      }
#ifdef XFSERRORDEBUG
      xfs_buftrace("XFS BUFCB NOERR", bp);
#endif
      xfs_buf_do_callbacks(bp, lip);
      XFS_BUF_SET_FSPRIVATE(bp, NULL);
      XFS_BUF_CLR_IODONE_FUNC(bp);
      xfs_biodone(bp);
}

/*
 * This is a callback routine attached to a buffer which gets an error
 * when being written out synchronously.
 */
STATIC void
xfs_buf_error_relse(
      xfs_buf_t   *bp)
{
      xfs_log_item_t    *lip;
      xfs_mount_t *mp;

      lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
      mp = (xfs_mount_t *)lip->li_mountp;
      ASSERT(XFS_BUF_TARGET(bp) == mp->m_ddev_targp);

      XFS_BUF_STALE(bp);
      XFS_BUF_DONE(bp);
      XFS_BUF_UNDELAYWRITE(bp);
      XFS_BUF_ERROR(bp,0);
      xfs_buftrace("BUF_ERROR_RELSE", bp);
      if (! XFS_FORCED_SHUTDOWN(mp))
            xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
      /*
       * We have to unpin the pinned buffers so do the
       * callbacks.
       */
      xfs_buf_do_callbacks(bp, lip);
      XFS_BUF_SET_FSPRIVATE(bp, NULL);
      XFS_BUF_CLR_IODONE_FUNC(bp);
      XFS_BUF_SET_BRELSE_FUNC(bp,NULL);
      xfs_buf_relse(bp);
}


/*
 * This is the iodone() function for buffers which have been
 * logged.  It is called when they are eventually flushed out.
 * It should remove the buf item from the AIL, and free the buf item.
 * It is called by xfs_buf_iodone_callbacks() above which will take
 * care of cleaning up the buffer itself.
 */
/* ARGSUSED */
void
xfs_buf_iodone(
      xfs_buf_t         *bp,
      xfs_buf_log_item_t      *bip)
{
      struct xfs_mount  *mp;
      SPLDECL(s);

      ASSERT(bip->bli_buf == bp);

      mp = bip->bli_item.li_mountp;

      /*
       * If we are forcibly shutting down, this may well be
       * off the AIL already. That's because we simulate the
       * log-committed callbacks to unpin these buffers. Or we may never
       * have put this item on AIL because of the transaction was
       * aborted forcibly. xfs_trans_delete_ail() takes care of these.
       *
       * Either way, AIL is useless if we're forcing a shutdown.
       */
      AIL_LOCK(mp,s);
      /*
       * xfs_trans_delete_ail() drops the AIL lock.
       */
      xfs_trans_delete_ail(mp, (xfs_log_item_t *)bip, s);

#ifdef XFS_TRANS_DEBUG
      kmem_free(bip->bli_orig, XFS_BUF_COUNT(bp));
      bip->bli_orig = NULL;
      kmem_free(bip->bli_logged, XFS_BUF_COUNT(bp) / NBBY);
      bip->bli_logged = NULL;
#endif /* XFS_TRANS_DEBUG */

#ifdef XFS_BLI_TRACE
      ktrace_free(bip->bli_trace);
#endif
      kmem_zone_free(xfs_buf_item_zone, bip);
}

#if defined(XFS_BLI_TRACE)
void
xfs_buf_item_trace(
      char              *id,
      xfs_buf_log_item_t      *bip)
{
      xfs_buf_t         *bp;
      ASSERT(bip->bli_trace != NULL);

      bp = bip->bli_buf;
      ktrace_enter(bip->bli_trace,
                 (void *)id,
                 (void *)bip->bli_buf,
                 (void *)((unsigned long)bip->bli_flags),
                 (void *)((unsigned long)bip->bli_recur),
                 (void *)((unsigned long)atomic_read(&bip->bli_refcount)),
                 (void *)((unsigned long)
                        (0xFFFFFFFF & XFS_BUF_ADDR(bp) >> 32)),
                 (void *)((unsigned long)(0xFFFFFFFF & XFS_BUF_ADDR(bp))),
                 (void *)((unsigned long)XFS_BUF_COUNT(bp)),
                 (void *)((unsigned long)XFS_BUF_BFLAGS(bp)),
                 XFS_BUF_FSPRIVATE(bp, void *),
                 XFS_BUF_FSPRIVATE2(bp, void *),
                 (void *)(unsigned long)XFS_BUF_ISPINNED(bp),
                 (void *)XFS_BUF_IODONE_FUNC(bp),
                 (void *)((unsigned long)(XFS_BUF_VALUSEMA(bp))),
                 (void *)bip->bli_item.li_desc,
                 (void *)((unsigned long)bip->bli_item.li_flags));
}
#endif /* XFS_BLI_TRACE */

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