OSCL-LXR linux-6.0.1/​fs/​xfs/​xfs_buf_item.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  * All Rights Reserved.
  */
 #include "xfs.h"
 #include "xfs_fs.h"
 #include "xfs_shared.h"
 #include "xfs_format.h"
 #include "xfs_log_format.h"
 #include "xfs_trans_resv.h"
 #include "xfs_bit.h"
 #include "xfs_mount.h"
 #include "xfs_trans.h"
 #include "xfs_trans_priv.h"
 #include "xfs_buf_item.h"
 #include "xfs_inode.h"
 #include "xfs_inode_item.h"
 #include "xfs_quota.h"
 #include "xfs_dquot_item.h"
 #include "xfs_dquot.h"
 #include "xfs_trace.h"
 #include "xfs_log.h"
 #include "xfs_log_priv.h"
 
 
 struct kmem_cache   *xfs_buf_item_cache;
 
 static inline struct xfs_buf_log_item *BUF_ITEM(struct xfs_log_item *lip)
 {
     return container_of(lip, struct xfs_buf_log_item, bli_item);
 }
 
 /* Is this log iovec plausibly large enough to contain the buffer log format? */
 bool
 xfs_buf_log_check_iovec(
     struct xfs_log_iovec        *iovec)
 {
     struct xfs_buf_log_format   *blfp = iovec->i_addr;
     char                *bmp_end;
     char                *item_end;
 
     if (offsetof(struct xfs_buf_log_format, blf_data_map) > iovec->i_len)
         return false;
 
     item_end = (char *)iovec->i_addr + iovec->i_len;
     bmp_end = (char *)&blfp->blf_data_map[blfp->blf_map_size];
     return bmp_end <= item_end;
 }
 
 static inline int
 xfs_buf_log_format_size(
     struct xfs_buf_log_format *blfp)
 {
     return offsetof(struct xfs_buf_log_format, blf_data_map) +
             (blfp->blf_map_size * sizeof(blfp->blf_data_map[0]));
 }
 
 static inline bool
 xfs_buf_item_straddle(
     struct xfs_buf      *bp,
     uint            offset,
     int         first_bit,
     int         nbits)
 {
     void            *first, *last;
 
     first = xfs_buf_offset(bp, offset + (first_bit << XFS_BLF_SHIFT));
     last = xfs_buf_offset(bp,
             offset + ((first_bit + nbits) << XFS_BLF_SHIFT));
 
     if (last - first != nbits * XFS_BLF_CHUNK)
         return true;
     return false;
 }
 
 /*
  * Return the number of log iovecs and space needed to log the given buf log
  * item segment.
  *
  * 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.
  */
 STATIC void
 xfs_buf_item_size_segment(
     struct xfs_buf_log_item     *bip,
     struct xfs_buf_log_format   *blfp,
     uint                offset,
     int             *nvecs,
     int             *nbytes)
 {
     struct xfs_buf          *bp = bip->bli_buf;
     int             first_bit;
     int             nbits;
     int             next_bit;
     int             last_bit;
 
     first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size, 0);
     if (first_bit == -1)
         return;
 
     (*nvecs)++;
     *nbytes += xfs_buf_log_format_size(blfp);
 
     do {
         nbits = xfs_contig_bits(blfp->blf_data_map,
                     blfp->blf_map_size, first_bit);
         ASSERT(nbits > 0);
 
         /*
          * Straddling a page is rare because we don't log contiguous
          * chunks of unmapped buffers anywhere.
          */
         if (nbits > 1 &&
             xfs_buf_item_straddle(bp, offset, first_bit, nbits))
             goto slow_scan;
 
         (*nvecs)++;
         *nbytes += nbits * XFS_BLF_CHUNK;
 
         /*
          * 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.
          */
         first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size,
                     (uint)first_bit + nbits + 1);
     } while (first_bit != -1);
 
     return;
 
 slow_scan:
     /* Count the first bit we jumped out of the above loop from */
     (*nvecs)++;
     *nbytes += XFS_BLF_CHUNK;
     last_bit = first_bit;
     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(blfp->blf_data_map, blfp->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) {
             break;
         } else if (next_bit != last_bit + 1 ||
                    xfs_buf_item_straddle(bp, offset, first_bit, nbits)) {
             last_bit = next_bit;
             first_bit = next_bit;
             (*nvecs)++;
             nbits = 1;
         } else {
             last_bit++;
             nbits++;
         }
         *nbytes += XFS_BLF_CHUNK;
     }
 }
 
 /*
  * Return the number of log iovecs and space needed to log the given buf log
  * item.
  *
  * Discontiguous buffers need a format structure per region that is being
  * logged. This makes the changes in the buffer appear to log recovery as though
  * they came from separate buffers, just like would occur if multiple buffers
  * were used instead of a single discontiguous buffer. This enables
  * discontiguous buffers to be in-memory constructs, completely transparent to
  * what ends up on disk.
  *
  * If the XFS_BLI_STALE flag has been set, then log nothing but the buf log
  * format structures. If the item has previously been logged and has dirty
  * regions, we do not relog them in stale buffers. This has the effect of
  * reducing the size of the relogged item by the amount of dirty data tracked
  * by the log item. This can result in the committing transaction reducing the
  * amount of space being consumed by the CIL.
  */
 STATIC void
 xfs_buf_item_size(
     struct xfs_log_item *lip,
     int         *nvecs,
     int         *nbytes)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
     struct xfs_buf      *bp = bip->bli_buf;
     int         i;
     int         bytes;
     uint            offset = 0;
 
     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 as we are never
          * going to replay the changes tracked in the log item.
          */
         trace_xfs_buf_item_size_stale(bip);
         ASSERT(bip->__bli_format.blf_flags & XFS_BLF_CANCEL);
         *nvecs += bip->bli_format_count;
         for (i = 0; i < bip->bli_format_count; i++) {
             *nbytes += xfs_buf_log_format_size(&bip->bli_formats[i]);
         }
         return;
     }
 
     ASSERT(bip->bli_flags & XFS_BLI_LOGGED);
 
     if (bip->bli_flags & XFS_BLI_ORDERED) {
         /*
          * The buffer has been logged just to order it. It is not being
          * included in the transaction commit, so no vectors are used at
          * all.
          */
         trace_xfs_buf_item_size_ordered(bip);
         *nvecs = XFS_LOG_VEC_ORDERED;
         return;
     }
 
     /*
      * The vector count is based on the number of buffer vectors we have
      * dirty bits in. This will only be greater than one when we have a
      * compound buffer with more than one segment dirty. Hence for compound
      * buffers we need to track which segment the dirty bits correspond to,
      * and when we move from one segment to the next increment the vector
      * count for the extra buf log format structure that will need to be
      * written.
      */
     bytes = 0;
     for (i = 0; i < bip->bli_format_count; i++) {
         xfs_buf_item_size_segment(bip, &bip->bli_formats[i], offset,
                       nvecs, &bytes);
         offset += BBTOB(bp->b_maps[i].bm_len);
     }
 
     /*
      * Round up the buffer size required to minimise the number of memory
      * allocations that need to be done as this item grows when relogged by
      * repeated modifications.
      */
     *nbytes = round_up(bytes, 512);
     trace_xfs_buf_item_size(bip);
 }
 
 static inline void
 xfs_buf_item_copy_iovec(
     struct xfs_log_vec  *lv,
     struct xfs_log_iovec    **vecp,
     struct xfs_buf      *bp,
     uint            offset,
     int         first_bit,
     uint            nbits)
 {
     offset += first_bit * XFS_BLF_CHUNK;
     xlog_copy_iovec(lv, vecp, XLOG_REG_TYPE_BCHUNK,
             xfs_buf_offset(bp, offset),
             nbits * XFS_BLF_CHUNK);
 }
 
 static void
 xfs_buf_item_format_segment(
     struct xfs_buf_log_item *bip,
     struct xfs_log_vec  *lv,
     struct xfs_log_iovec    **vecp,
     uint            offset,
     struct xfs_buf_log_format *blfp)
 {
     struct xfs_buf      *bp = bip->bli_buf;
     uint            base_size;
     int         first_bit;
     int         last_bit;
     int         next_bit;
     uint            nbits;
 
     /* copy the flags across from the base format item */
     blfp->blf_flags = bip->__bli_format.blf_flags;
 
     /*
      * Base size is the actual size of the ondisk structure - it reflects
      * the actual size of the dirty bitmap rather than the size of the in
      * memory structure.
      */
     base_size = xfs_buf_log_format_size(blfp);
 
     first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size, 0);
     if (!(bip->bli_flags & XFS_BLI_STALE) && first_bit == -1) {
         /*
          * If the map is not be dirty in the transaction, mark
          * the size as zero and do not advance the vector pointer.
          */
         return;
     }
 
     blfp = xlog_copy_iovec(lv, vecp, XLOG_REG_TYPE_BFORMAT, blfp, base_size);
     blfp->blf_size = 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.
          */
         trace_xfs_buf_item_format_stale(bip);
         ASSERT(blfp->blf_flags & XFS_BLF_CANCEL);
         return;
     }
 
 
     /*
      * Fill in an iovec for each set of contiguous chunks.
      */
     do {
         ASSERT(first_bit >= 0);
         nbits = xfs_contig_bits(blfp->blf_data_map,
                     blfp->blf_map_size, first_bit);
         ASSERT(nbits > 0);
 
         /*
          * Straddling a page is rare because we don't log contiguous
          * chunks of unmapped buffers anywhere.
          */
         if (nbits > 1 &&
             xfs_buf_item_straddle(bp, offset, first_bit, nbits))
             goto slow_scan;
 
         xfs_buf_item_copy_iovec(lv, vecp, bp, offset,
                     first_bit, nbits);
         blfp->blf_size++;
 
         /*
          * 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.
          */
         first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size,
                     (uint)first_bit + nbits + 1);
     } while (first_bit != -1);
 
     return;
 
 slow_scan:
     ASSERT(bp->b_addr == NULL);
     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(blfp->blf_data_map, blfp->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) {
             xfs_buf_item_copy_iovec(lv, vecp, bp, offset,
                         first_bit, nbits);
             blfp->blf_size++;
             break;
         } else if (next_bit != last_bit + 1 ||
                    xfs_buf_item_straddle(bp, offset, first_bit, nbits)) {
             xfs_buf_item_copy_iovec(lv, vecp, bp, offset,
                         first_bit, nbits);
             blfp->blf_size++;
             first_bit = next_bit;
             last_bit = next_bit;
             nbits = 1;
         } else {
             last_bit++;
             nbits++;
         }
     }
 }
 
 /*
  * 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(
     struct xfs_log_item *lip,
     struct xfs_log_vec  *lv)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
     struct xfs_buf      *bp = bip->bli_buf;
     struct xfs_log_iovec    *vecp = NULL;
     uint            offset = 0;
     int         i;
 
     ASSERT(atomic_read(&bip->bli_refcount) > 0);
     ASSERT((bip->bli_flags & XFS_BLI_LOGGED) ||
            (bip->bli_flags & XFS_BLI_STALE));
     ASSERT((bip->bli_flags & XFS_BLI_STALE) ||
            (xfs_blft_from_flags(&bip->__bli_format) > XFS_BLFT_UNKNOWN_BUF
             && xfs_blft_from_flags(&bip->__bli_format) < XFS_BLFT_MAX_BUF));
     ASSERT(!(bip->bli_flags & XFS_BLI_ORDERED) ||
            (bip->bli_flags & XFS_BLI_STALE));
 
 
     /*
      * If it is an inode buffer, transfer the in-memory state to the
      * format flags and clear the in-memory state.
      *
      * For buffer based inode allocation, we do not transfer
      * this state if the inode buffer allocation has not yet been committed
      * to the log as setting the XFS_BLI_INODE_BUF flag will prevent
      * correct replay of the inode allocation.
      *
      * For icreate item based inode allocation, the buffers aren't written
      * to the journal during allocation, and hence we should always tag the
      * buffer as an inode buffer so that the correct unlinked list replay
      * occurs during recovery.
      */
     if (bip->bli_flags & XFS_BLI_INODE_BUF) {
         if (xfs_has_v3inodes(lip->li_log->l_mp) ||
             !((bip->bli_flags & XFS_BLI_INODE_ALLOC_BUF) &&
               xfs_log_item_in_current_chkpt(lip)))
             bip->__bli_format.blf_flags |= XFS_BLF_INODE_BUF;
         bip->bli_flags &= ~XFS_BLI_INODE_BUF;
     }
 
     for (i = 0; i < bip->bli_format_count; i++) {
         xfs_buf_item_format_segment(bip, lv, &vecp, offset,
                         &bip->bli_formats[i]);
         offset += BBTOB(bp->b_maps[i].bm_len);
     }
 
     /*
      * Check to make sure everything is consistent.
      */
     trace_xfs_buf_item_format(bip);
 }
 
 /*
  * This is called to pin the buffer associated with the buf log item in memory
  * so it cannot be written out.
  *
  * We also always take a reference to the buffer log item here so that the bli
  * is held while the item is pinned in memory. This means that we can
  * unconditionally drop the reference count a transaction holds when the
  * transaction is completed.
  */
 STATIC void
 xfs_buf_item_pin(
     struct xfs_log_item *lip)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
 
     ASSERT(atomic_read(&bip->bli_refcount) > 0);
     ASSERT((bip->bli_flags & XFS_BLI_LOGGED) ||
            (bip->bli_flags & XFS_BLI_ORDERED) ||
            (bip->bli_flags & XFS_BLI_STALE));
 
     trace_xfs_buf_item_pin(bip);
 
     atomic_inc(&bip->bli_refcount);
     atomic_inc(&bip->bli_buf->b_pin_count);
 }
 
 /*
  * 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().
  */
 STATIC void
 xfs_buf_item_unpin(
     struct xfs_log_item *lip,
     int         remove)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
     struct xfs_buf      *bp = bip->bli_buf;
     int         stale = bip->bli_flags & XFS_BLI_STALE;
     int         freed;
 
     ASSERT(bp->b_log_item == bip);
     ASSERT(atomic_read(&bip->bli_refcount) > 0);
 
     trace_xfs_buf_item_unpin(bip);
 
     /*
      * Drop the bli ref associated with the pin and grab the hold required
      * for the I/O simulation failure in the abort case. We have to do this
      * before the pin count drops because the AIL doesn't acquire a bli
      * reference. Therefore if the refcount drops to zero, the bli could
      * still be AIL resident and the buffer submitted for I/O (and freed on
      * completion) at any point before we return. This can be removed once
      * the AIL properly holds a reference on the bli.
      */
     freed = atomic_dec_and_test(&bip->bli_refcount);
     if (freed && !stale && remove)
         xfs_buf_hold(bp);
     if (atomic_dec_and_test(&bp->b_pin_count))
         wake_up_all(&bp->b_waiters);
 
      /* nothing to do but drop the pin count if the bli is active */
     if (!freed)
         return;
 
     if (stale) {
         ASSERT(bip->bli_flags & XFS_BLI_STALE);
         ASSERT(xfs_buf_islocked(bp));
         ASSERT(bp->b_flags & XBF_STALE);
         ASSERT(bip->__bli_format.blf_flags & XFS_BLF_CANCEL);
         ASSERT(list_empty(&lip->li_trans));
         ASSERT(!bp->b_transp);
 
         trace_xfs_buf_item_unpin_stale(bip);
 
         /*
          * If we get called here because of an IO error, we may or may
          * not have the item on the AIL. xfs_trans_ail_delete() will
          * take care of that situation. xfs_trans_ail_delete() drops
          * the AIL lock.
          */
         if (bip->bli_flags & XFS_BLI_STALE_INODE) {
             xfs_buf_item_done(bp);
             xfs_buf_inode_iodone(bp);
             ASSERT(list_empty(&bp->b_li_list));
         } else {
             xfs_trans_ail_delete(lip, SHUTDOWN_LOG_IO_ERROR);
             xfs_buf_item_relse(bp);
             ASSERT(bp->b_log_item == NULL);
         }
         xfs_buf_relse(bp);
     } else if (remove) {
         /*
          * The buffer must be locked and held by the caller to simulate
          * an async I/O failure. We acquired the hold for this case
          * before the buffer was unpinned.
          */
         xfs_buf_lock(bp);
         bp->b_flags |= XBF_ASYNC;
         xfs_buf_ioend_fail(bp);
     }
 }
 
 STATIC uint
 xfs_buf_item_push(
     struct xfs_log_item *lip,
     struct list_head    *buffer_list)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
     struct xfs_buf      *bp = bip->bli_buf;
     uint            rval = XFS_ITEM_SUCCESS;
 
     if (xfs_buf_ispinned(bp))
         return XFS_ITEM_PINNED;
     if (!xfs_buf_trylock(bp)) {
         /*
          * If we have just raced with a buffer being pinned and it has
          * been marked stale, we could end up stalling until someone else
          * issues a log force to unpin the stale buffer. Check for the
          * race condition here so xfsaild recognizes the buffer is pinned
          * and queues a log force to move it along.
          */
         if (xfs_buf_ispinned(bp))
             return XFS_ITEM_PINNED;
         return XFS_ITEM_LOCKED;
     }
 
     ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
 
     trace_xfs_buf_item_push(bip);
 
     /* has a previous flush failed due to IO errors? */
     if (bp->b_flags & XBF_WRITE_FAIL) {
         xfs_buf_alert_ratelimited(bp, "XFS: Failing async write",
         "Failing async write on buffer block 0x%llx. Retrying async write.",
                       (long long)xfs_buf_daddr(bp));
     }
 
     if (!xfs_buf_delwri_queue(bp, buffer_list))
         rval = XFS_ITEM_FLUSHING;
     xfs_buf_unlock(bp);
     return rval;
 }
 
 /*
  * Drop the buffer log item refcount and take appropriate action. This helper
  * determines whether the bli must be freed or not, since a decrement to zero
  * does not necessarily mean the bli is unused.
  *
  * Return true if the bli is freed, false otherwise.
  */
 bool
 xfs_buf_item_put(
     struct xfs_buf_log_item *bip)
 {
     struct xfs_log_item *lip = &bip->bli_item;
     bool            aborted;
     bool            dirty;
 
     /* drop the bli ref and return if it wasn't the last one */
     if (!atomic_dec_and_test(&bip->bli_refcount))
         return false;
 
     /*
      * We dropped the last ref and must free the item if clean or aborted.
      * If the bli is dirty and non-aborted, the buffer was clean in the
      * transaction but still awaiting writeback from previous changes. In
      * that case, the bli is freed on buffer writeback completion.
      */
     aborted = test_bit(XFS_LI_ABORTED, &lip->li_flags) ||
             xlog_is_shutdown(lip->li_log);
     dirty = bip->bli_flags & XFS_BLI_DIRTY;
     if (dirty && !aborted)
         return false;
 
     /*
      * The bli is aborted or clean. An aborted item may be in the AIL
      * regardless of dirty state.  For example, consider an aborted
      * transaction that invalidated a dirty bli and cleared the dirty
      * state.
      */
     if (aborted)
         xfs_trans_ail_delete(lip, 0);
     xfs_buf_item_relse(bip->bli_buf);
     return true;
 }
 
 /*
  * 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.
  *
  * We unconditionally drop the transaction's reference to the log item. If the
  * item was logged, then another reference was taken when it was pinned, so we
  * can safely drop the transaction reference now.  This also allows us to avoid
  * potential races with the unpin code freeing the bli by not referencing the
  * bli after we've dropped the reference 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_release(
     struct xfs_log_item *lip)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
     struct xfs_buf      *bp = bip->bli_buf;
     bool            released;
     bool            hold = bip->bli_flags & XFS_BLI_HOLD;
     bool            stale = bip->bli_flags & XFS_BLI_STALE;
 #if defined(DEBUG) || defined(XFS_WARN)
     bool            ordered = bip->bli_flags & XFS_BLI_ORDERED;
     bool            dirty = bip->bli_flags & XFS_BLI_DIRTY;
     bool            aborted = test_bit(XFS_LI_ABORTED,
                            &lip->li_flags);
 #endif
 
     trace_xfs_buf_item_release(bip);
 
     /*
      * The bli dirty state should match whether the blf has logged segments
      * except for ordered buffers, where only the bli should be dirty.
      */
     ASSERT((!ordered && dirty == xfs_buf_item_dirty_format(bip)) ||
            (ordered && dirty && !xfs_buf_item_dirty_format(bip)));
     ASSERT(!stale || (bip->__bli_format.blf_flags & XFS_BLF_CANCEL));
 
     /*
      * Clear the buffer's association with this transaction and
      * per-transaction state from the bli, which has been copied above.
      */
     bp->b_transp = NULL;
     bip->bli_flags &= ~(XFS_BLI_LOGGED | XFS_BLI_HOLD | XFS_BLI_ORDERED);
 
     /*
      * Unref the item and unlock the buffer unless held or stale. Stale
      * buffers remain locked until final unpin unless the bli is freed by
      * the unref call. The latter implies shutdown because buffer
      * invalidation dirties the bli and transaction.
      */
     released = xfs_buf_item_put(bip);
     if (hold || (stale && !released))
         return;
     ASSERT(!stale || aborted);
     xfs_buf_relse(bp);
 }
 
 STATIC void
 xfs_buf_item_committing(
     struct xfs_log_item *lip,
     xfs_csn_t       seq)
 {
     return xfs_buf_item_release(lip);
 }
 
 /*
  * 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(
     struct xfs_log_item *lip,
     xfs_lsn_t       lsn)
 {
     struct xfs_buf_log_item *bip = BUF_ITEM(lip);
 
     trace_xfs_buf_item_committed(bip);
 
     if ((bip->bli_flags & XFS_BLI_INODE_ALLOC_BUF) && lip->li_lsn != 0)
         return lip->li_lsn;
     return lsn;
 }
 
 static const struct xfs_item_ops xfs_buf_item_ops = {
     .iop_size   = xfs_buf_item_size,
     .iop_format = xfs_buf_item_format,
     .iop_pin    = xfs_buf_item_pin,
     .iop_unpin  = xfs_buf_item_unpin,
     .iop_release    = xfs_buf_item_release,
     .iop_committing = xfs_buf_item_committing,
     .iop_committed  = xfs_buf_item_committed,
     .iop_push   = xfs_buf_item_push,
 };
 
 STATIC void
 xfs_buf_item_get_format(
     struct xfs_buf_log_item *bip,
     int         count)
 {
     ASSERT(bip->bli_formats == NULL);
     bip->bli_format_count = count;
 
     if (count == 1) {
         bip->bli_formats = &bip->__bli_format;
         return;
     }
 
     bip->bli_formats = kmem_zalloc(count * sizeof(struct xfs_buf_log_format),
                 0);
 }
 
 STATIC void
 xfs_buf_item_free_format(
     struct xfs_buf_log_item *bip)
 {
     if (bip->bli_formats != &bip->__bli_format) {
         kmem_free(bip->bli_formats);
         bip->bli_formats = NULL;
     }
 }
 
 /*
  * Allocate a new buf log item to go with the given buffer.
  * Set the buffer's b_log_item field to point to the new
  * buf log item.
  */
 int
 xfs_buf_item_init(
     struct xfs_buf  *bp,
     struct xfs_mount *mp)
 {
     struct xfs_buf_log_item *bip = bp->b_log_item;
     int         chunks;
     int         map_size;
     int         i;
 
     /*
      * Check to see if there is already a buf log item for
      * this buffer. If we do already have one, there is
      * nothing to do here so return.
      */
     ASSERT(bp->b_mount == mp);
     if (bip) {
         ASSERT(bip->bli_item.li_type == XFS_LI_BUF);
         ASSERT(!bp->b_transp);
         ASSERT(bip->bli_buf == bp);
         return 0;
     }
 
     bip = kmem_cache_zalloc(xfs_buf_item_cache, GFP_KERNEL | __GFP_NOFAIL);
     xfs_log_item_init(mp, &bip->bli_item, XFS_LI_BUF, &xfs_buf_item_ops);
     bip->bli_buf = bp;
 
     /*
      * chunks is the number of XFS_BLF_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.
      *
      * Discontiguous buffer support follows the layout of the underlying
      * buffer. This makes the implementation as simple as possible.
      */
     xfs_buf_item_get_format(bip, bp->b_map_count);
 
     for (i = 0; i < bip->bli_format_count; i++) {
         chunks = DIV_ROUND_UP(BBTOB(bp->b_maps[i].bm_len),
                       XFS_BLF_CHUNK);
         map_size = DIV_ROUND_UP(chunks, NBWORD);
 
         if (map_size > XFS_BLF_DATAMAP_SIZE) {
             kmem_cache_free(xfs_buf_item_cache, bip);
             xfs_err(mp,
     "buffer item dirty bitmap (%u uints) too small to reflect %u bytes!",
                     map_size,
                     BBTOB(bp->b_maps[i].bm_len));
             return -EFSCORRUPTED;
         }
 
         bip->bli_formats[i].blf_type = XFS_LI_BUF;
         bip->bli_formats[i].blf_blkno = bp->b_maps[i].bm_bn;
         bip->bli_formats[i].blf_len = bp->b_maps[i].bm_len;
         bip->bli_formats[i].blf_map_size = map_size;
     }
 
     bp->b_log_item = bip;
     xfs_buf_hold(bp);
     return 0;
 }
 
 
 /*
  * Mark bytes first through last inclusive as dirty in the buf
  * item's bitmap.
  */
 static void
 xfs_buf_item_log_segment(
     uint            first,
     uint            last,
     uint            *map)
 {
     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;
 
     ASSERT(first < XFS_BLF_DATAMAP_SIZE * XFS_BLF_CHUNK * NBWORD);
     ASSERT(last < XFS_BLF_DATAMAP_SIZE * XFS_BLF_CHUNK * NBWORD);
 
     /*
      * Convert byte offsets to bit numbers.
      */
     first_bit = first >> XFS_BLF_SHIFT;
     last_bit = last >> XFS_BLF_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 = &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 = ((1U << (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 = (1U << end_bit) - 1;
         *wordp |= mask;
     }
 }
 
 /*
  * Mark bytes first through last inclusive as dirty in the buf
  * item's bitmap.
  */
 void
 xfs_buf_item_log(
     struct xfs_buf_log_item *bip,
     uint            first,
     uint            last)
 {
     int         i;
     uint            start;
     uint            end;
     struct xfs_buf      *bp = bip->bli_buf;
 
     /*
      * walk each buffer segment and mark them dirty appropriately.
      */
     start = 0;
     for (i = 0; i < bip->bli_format_count; i++) {
         if (start > last)
             break;
         end = start + BBTOB(bp->b_maps[i].bm_len) - 1;
 
         /* skip to the map that includes the first byte to log */
         if (first > end) {
             start += BBTOB(bp->b_maps[i].bm_len);
             continue;
         }
 
         /*
          * Trim the range to this segment and mark it in the bitmap.
          * Note that we must convert buffer offsets to segment relative
          * offsets (e.g., the first byte of each segment is byte 0 of
          * that segment).
          */
         if (first < start)
             first = start;
         if (end > last)
             end = last;
         xfs_buf_item_log_segment(first - start, end - start,
                      &bip->bli_formats[i].blf_data_map[0]);
 
         start += BBTOB(bp->b_maps[i].bm_len);
     }
 }
 
 
 /*
  * Return true if the buffer has any ranges logged/dirtied by a transaction,
  * false otherwise.
  */
 bool
 xfs_buf_item_dirty_format(
     struct xfs_buf_log_item *bip)
 {
     int         i;
 
     for (i = 0; i < bip->bli_format_count; i++) {
         if (!xfs_bitmap_empty(bip->bli_formats[i].blf_data_map,
                  bip->bli_formats[i].blf_map_size))
             return true;
     }
 
     return false;
 }
 
 STATIC void
 xfs_buf_item_free(
     struct xfs_buf_log_item *bip)
 {
     xfs_buf_item_free_format(bip);
     kmem_free(bip->bli_item.li_lv_shadow);
     kmem_cache_free(xfs_buf_item_cache, bip);
 }
 
 /*
  * xfs_buf_item_relse() is called when the buf log item is no longer needed.
  */
 void
 xfs_buf_item_relse(
     struct xfs_buf  *bp)
 {
     struct xfs_buf_log_item *bip = bp->b_log_item;
 
     trace_xfs_buf_item_relse(bp, _RET_IP_);
     ASSERT(!test_bit(XFS_LI_IN_AIL, &bip->bli_item.li_flags));
 
     bp->b_log_item = NULL;
     xfs_buf_rele(bp);
     xfs_buf_item_free(bip);
 }
 
 void
 xfs_buf_item_done(
     struct xfs_buf      *bp)
 {
     /*
      * 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_ail_delete() takes care of these.
      *
      * Either way, AIL is useless if we're forcing a shutdown.
      *
      * Note that log recovery writes might have buffer items that are not on
      * the AIL even when the file system is not shut down.
      */
     xfs_trans_ail_delete(&bp->b_log_item->bli_item,
                  (bp->b_flags & _XBF_LOGRECOVERY) ? 0 :
                  SHUTDOWN_CORRUPT_INCORE);
     xfs_buf_item_relse(bp);
 }

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