Initial file dump from open source releaseHEADmaster

1 files changed, 1100 insertions, 0 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
new file mode 100644
index 00000000..4ec43177
--- /dev/null
+++ b/fs/xfs/xfs_buf_item.c
@@ -0,0 +1,1100 @@
+/*
+ * 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_trans.h"
+#include "xfs_sb.h"
+#include "xfs_ag.h"
+#include "xfs_mount.h"
+#include "xfs_buf_item.h"
+#include "xfs_trans_priv.h"
+#include "xfs_error.h"
+#include "xfs_trace.h"
+
+
+kmem_zone_t	*xfs_buf_item_zone;
+
+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);
+}
+
+STATIC void	xfs_buf_do_callbacks(struct xfs_buf *bp);
+
+/*
+ * 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_segment(
+	struct xfs_buf_log_item	*bip,
+	struct xfs_buf_log_format *blfp)
+{
+	struct xfs_buf		*bp = bip->bli_buf;
+	uint			nvecs;
+	int			next_bit;
+	int			last_bit;
+
+	last_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size, 0);
+	if (last_bit == -1)
+		return 0;
+
+	/*
+	 * initial count for a dirty buffer is 2 vectors - the format structure
+	 * and the first dirty region.
+	 */
+	nvecs = 2;
+
+	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) {
+			last_bit = next_bit;
+			nvecs++;
+		} else if (xfs_buf_offset(bp, next_bit * XFS_BLF_CHUNK) !=
+			   (xfs_buf_offset(bp, last_bit * XFS_BLF_CHUNK) +
+			    XFS_BLF_CHUNK)) {
+			last_bit = next_bit;
+			nvecs++;
+		} else {
+			last_bit++;
+		}
+	}
+
+	return nvecs;
+}
+
+/*
+ * 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.
+ *
+ * Discontiguous buffers need a format structure per region that 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.
+ */
+STATIC uint
+xfs_buf_item_size(
+	struct xfs_log_item	*lip)
+{
+	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
+	uint			nvecs;
+	int			i;
+
+	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.
+		 */
+		trace_xfs_buf_item_size_stale(bip);
+		ASSERT(bip->__bli_format.blf_flags & XFS_BLF_CANCEL);
+		return bip->bli_format_count;
+	}
+
+	ASSERT(bip->bli_flags & XFS_BLI_LOGGED);
+
+	/*
+	 * 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.
+	 */
+	nvecs = 0;
+	for (i = 0; i < bip->bli_format_count; i++) {
+		nvecs += xfs_buf_item_size_segment(bip, &bip->bli_formats[i]);
+	}
+
+	trace_xfs_buf_item_size(bip);
+	return nvecs;
+}
+
+static struct xfs_log_iovec *
+xfs_buf_item_format_segment(
+	struct xfs_buf_log_item	*bip,
+	struct xfs_log_iovec	*vecp,
+	uint			offset,
+	struct xfs_buf_log_format *blfp)
+{
+	struct xfs_buf	*bp = bip->bli_buf;
+	uint		base_size;
+	uint		nvecs;
+	int		first_bit;
+	int		last_bit;
+	int		next_bit;
+	uint		nbits;
+	uint		buffer_offset;
+
+	/* 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 = offsetof(struct xfs_buf_log_format, blf_data_map) +
+			(blfp->blf_map_size * sizeof(blfp->blf_data_map[0]));
+
+	nvecs = 0;
+	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.
+		 */
+		goto out;
+	}
+
+	vecp->i_addr = blfp;
+	vecp->i_len = base_size;
+	vecp->i_type = 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.
+		 */
+		trace_xfs_buf_item_format_stale(bip);
+		ASSERT(blfp->blf_flags & XFS_BLF_CANCEL);
+		goto out;
+	}
+
+	/*
+	 * Fill in an iovec for each set of contiguous chunks.
+	 */
+
+	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) {
+			buffer_offset = offset + first_bit * XFS_BLF_CHUNK;
+			vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
+			vecp->i_len = nbits * XFS_BLF_CHUNK;
+			vecp->i_type = XLOG_REG_TYPE_BCHUNK;
+			nvecs++;
+			break;
+		} else if (next_bit != last_bit + 1) {
+			buffer_offset = offset + first_bit * XFS_BLF_CHUNK;
+			vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
+			vecp->i_len = nbits * XFS_BLF_CHUNK;
+			vecp->i_type = XLOG_REG_TYPE_BCHUNK;
+			nvecs++;
+			vecp++;
+			first_bit = next_bit;
+			last_bit = next_bit;
+			nbits = 1;
+		} else if (xfs_buf_offset(bp, offset +
+					      (next_bit << XFS_BLF_SHIFT)) !=
+			   (xfs_buf_offset(bp, offset +
+					       (last_bit << XFS_BLF_SHIFT)) +
+			    XFS_BLF_CHUNK)) {
+			buffer_offset = offset + first_bit * XFS_BLF_CHUNK;
+			vecp->i_addr = xfs_buf_offset(bp, buffer_offset);
+			vecp->i_len = nbits * XFS_BLF_CHUNK;
+			vecp->i_type = XLOG_REG_TYPE_BCHUNK;
+			nvecs++;
+			vecp++;
+			first_bit = next_bit;
+			last_bit = next_bit;
+			nbits = 1;
+		} else {
+			last_bit++;
+			nbits++;
+		}
+	}
+out:
+	blfp->blf_size = nvecs;
+	return vecp;
+}
+
+/*
+ * 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_iovec	*vecp)
+{
+	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
+	struct xfs_buf		*bp = bip->bli_buf;
+	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));
+
+	/*
+	 * If it is an inode buffer, transfer the in-memory state to the
+	 * format flags and clear the in-memory state. 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.
+	 */
+	if (bip->bli_flags & XFS_BLI_INODE_BUF) {
+		if (!((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++) {
+		vecp = xfs_buf_item_format_segment(bip, vecp, offset,
+						&bip->bli_formats[i]);
+		offset += 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_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().
+ *
+ * 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.
+ *
+ * If the remove flag is set we are called from uncommit in the
+ * forced-shutdown path.  If that is true and the reference count on
+ * the log item is going to drop to zero we need to free the item's
+ * descriptor in the transaction.
+ */
+STATIC void
+xfs_buf_item_unpin(
+	struct xfs_log_item	*lip,
+	int			remove)
+{
+	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
+	xfs_buf_t	*bp = bip->bli_buf;
+	struct xfs_ail	*ailp = lip->li_ailp;
+	int		stale = bip->bli_flags & XFS_BLI_STALE;
+	int		freed;
+
+	ASSERT(bp->b_fspriv == bip);
+	ASSERT(atomic_read(&bip->bli_refcount) > 0);
+
+	trace_xfs_buf_item_unpin(bip);
+
+	freed = atomic_dec_and_test(&bip->bli_refcount);
+
+	if (atomic_dec_and_test(&bp->b_pin_count))
+		wake_up_all(&bp->b_waiters);
+
+	if (freed && stale) {
+		ASSERT(bip->bli_flags & XFS_BLI_STALE);
+		ASSERT(xfs_buf_islocked(bp));
+		ASSERT(XFS_BUF_ISSTALE(bp));
+		ASSERT(bip->__bli_format.blf_flags & XFS_BLF_CANCEL);
+
+		trace_xfs_buf_item_unpin_stale(bip);
+
+		if (remove) {
+			/*
+			 * If we are in a transaction context, we have to
+			 * remove the log item from the transaction as we are
+			 * about to release our reference to the buffer.  If we
+			 * don't, the unlock that occurs later in
+			 * xfs_trans_uncommit() will try to reference the
+			 * buffer which we no longer have a hold on.
+			 */
+			if (lip->li_desc)
+				xfs_trans_del_item(lip);
+
+			/*
+			 * Since the transaction no longer refers to the buffer,
+			 * the buffer should no longer refer to the transaction.
+			 */
+			bp->b_transp = NULL;
+		}
+
+		/*
+		 * 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_do_callbacks(bp);
+			bp->b_fspriv = NULL;
+			bp->b_iodone = NULL;
+		} else {
+			spin_lock(&ailp->xa_lock);
+			xfs_trans_ail_delete(ailp, lip, SHUTDOWN_LOG_IO_ERROR);
+			xfs_buf_item_relse(bp);
+			ASSERT(bp->b_fspriv == NULL);
+		}
+		xfs_buf_relse(bp);
+	} else if (freed && remove) {
+		/*
+		 * There are currently two references to the buffer - the active
+		 * LRU reference and the buf log item. What we are about to do
+		 * here - simulate a failed IO completion - requires 3
+		 * references.
+		 *
+		 * The LRU reference is removed by the xfs_buf_stale() call. The
+		 * buf item reference is removed by the xfs_buf_iodone()
+		 * callback that is run by xfs_buf_do_callbacks() during ioend
+		 * processing (via the bp->b_iodone callback), and then finally
+		 * the ioend processing will drop the IO reference if the buffer
+		 * is marked XBF_ASYNC.
+		 *
+		 * Hence we need to take an additional reference here so that IO
+		 * completion processing doesn't free the buffer prematurely.
+		 */
+		xfs_buf_lock(bp);
+		xfs_buf_hold(bp);
+		bp->b_flags |= XBF_ASYNC;
+		xfs_buf_ioerror(bp, EIO);
+		XFS_BUF_UNDONE(bp);
+		xfs_buf_stale(bp);
+		xfs_buf_ioend(bp, 0);
+	}
+}
+
+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);
+
+	if (!xfs_buf_delwri_queue(bp, buffer_list))
+		rval = XFS_ITEM_FLUSHING;
+	xfs_buf_unlock(bp);
+	return rval;
+}
+
+/*
+ * 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_unlock(
+	struct xfs_log_item	*lip)
+{
+	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
+	struct xfs_buf		*bp = bip->bli_buf;
+	int			aborted, clean, i;
+	uint			hold;
+
+	/* Clear the buffer's association with this transaction. */
+	bp->b_transp = 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 = (lip->li_flags & XFS_LI_ABORTED) != 0;
+
+	/*
+	 * 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;
+
+	/* Clear the per transaction state. */
+	bip->bli_flags &= ~(XFS_BLI_LOGGED | XFS_BLI_HOLD);
+
+	/*
+	 * 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) {
+		trace_xfs_buf_item_unlock_stale(bip);
+		ASSERT(bip->__bli_format.blf_flags & XFS_BLF_CANCEL);
+		if (!aborted) {
+			atomic_dec(&bip->bli_refcount);
+			return;
+		}
+	}
+
+	trace_xfs_buf_item_unlock(bip);
+
+	/*
+	 * If the buf item isn't tracking any data, free it, otherwise drop the
+	 * reference we hold to it. If we are aborting the transaction, this may
+	 * be the only reference to the buf item, so we free it anyway
+	 * regardless of whether it is dirty or not. A dirty abort implies a
+	 * shutdown, anyway.
+	 */
+	clean = 1;
+	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)) {
+			clean = 0;
+			break;
+		}
+	}
+	if (clean)
+		xfs_buf_item_relse(bp);
+	else if (aborted) {
+		if (atomic_dec_and_test(&bip->bli_refcount)) {
+			ASSERT(XFS_FORCED_SHUTDOWN(lip->li_mountp));
+			xfs_buf_item_relse(bp);
+		}
+	} else
+		atomic_dec(&bip->bli_refcount);
+
+	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(
+	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 void
+xfs_buf_item_committing(
+	struct xfs_log_item	*lip,
+	xfs_lsn_t		commit_lsn)
+{
+}
+
+/*
+ * This is the ops vector shared by all buf log items.
+ */
+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_unlock	= xfs_buf_item_unlock,
+	.iop_committed	= xfs_buf_item_committed,
+	.iop_push	= xfs_buf_item_push,
+	.iop_committing = xfs_buf_item_committing
+};
+
+STATIC int
+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 0;
+	}
+
+	bip->bli_formats = kmem_zalloc(count * sizeof(struct xfs_buf_log_format),
+				KM_SLEEP);
+	if (!bip->bli_formats)
+		return ENOMEM;
+	return 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_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 = bp->b_fspriv;
+	xfs_buf_log_item_t	*bip;
+	int			chunks;
+	int			map_size;
+	int			error;
+	int			i;
+
+	/*
+	 * 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.
+	 */
+	ASSERT(bp->b_target->bt_mount == mp);
+	if (lip != NULL && lip->li_type == XFS_LI_BUF)
+		return;
+
+	bip = kmem_zone_zalloc(xfs_buf_item_zone, KM_SLEEP);
+	xfs_log_item_init(mp, &bip->bli_item, XFS_LI_BUF, &xfs_buf_item_ops);
+	bip->bli_buf = bp;
+	xfs_buf_hold(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.
+	 */
+	error = xfs_buf_item_get_format(bip, bp->b_map_count);
+	ASSERT(error == 0);
+
+	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);
+
+		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;
+	}
+
+#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 = kmem_alloc(BBTOB(bp->b_length), KM_SLEEP);
+	memcpy(bip->bli_orig, bp->b_addr, BBTOB(bp->b_length));
+	bip->bli_logged = kmem_zalloc(BBTOB(bp->b_length) / NBBY, KM_SLEEP);
+#endif
+
+	/*
+	 * Put the buf item into the list of items attached to the
+	 * buffer at the front.
+	 */
+	if (bp->b_fspriv)
+		bip->bli_item.li_bio_list = bp->b_fspriv;
+	bp->b_fspriv = bip;
+}
+
+
+/*
+ * Mark bytes first through last inclusive as dirty in the buf
+ * item's bitmap.
+ */
+void
+xfs_buf_item_log_segment(
+	struct xfs_buf_log_item	*bip,
+	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;
+
+	/*
+	 * 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 = ((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;
+	}
+}
+
+/*
+ * 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)
+{
+	int			i;
+	uint			start;
+	uint			end;
+	struct xfs_buf		*bp = bip->bli_buf;
+
+	/*
+	 * Mark the item as having some dirty data for
+	 * quick reference in xfs_buf_item_dirty.
+	 */
+	bip->bli_flags |= XFS_BLI_DIRTY;
+
+	/*
+	 * 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);
+		if (first > end) {
+			start += BBTOB(bp->b_maps[i].bm_len);
+			continue;
+		}
+		if (first < start)
+			first = start;
+		if (end > last)
+			end = last;
+
+		xfs_buf_item_log_segment(bip, first, end,
+					 &bip->bli_formats[i].blf_data_map[0]);
+
+		start += bp->b_maps[i].bm_len;
+	}
+}
+
+
+/*
+ * 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);
+}
+
+STATIC void
+xfs_buf_item_free(
+	xfs_buf_log_item_t	*bip)
+{
+#ifdef XFS_TRANS_DEBUG
+	kmem_free(bip->bli_orig);
+	kmem_free(bip->bli_logged);
+#endif /* XFS_TRANS_DEBUG */
+
+	xfs_buf_item_free_format(bip);
+	kmem_zone_free(xfs_buf_item_zone, bip);
+}
+
+/*
+ * 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;
+
+	trace_xfs_buf_item_relse(bp, _RET_IP_);
+
+	bip = bp->b_fspriv;
+	bp->b_fspriv = bip->bli_item.li_bio_list;
+	if (bp->b_fspriv == NULL)
+		bp->b_iodone = NULL;
+
+	xfs_buf_rele(bp);
+	xfs_buf_item_free(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_islocked(bp));
+
+	lip->li_cb = cb;
+	head_lip = bp->b_fspriv;
+	if (head_lip) {
+		lip->li_bio_list = head_lip->li_bio_list;
+		head_lip->li_bio_list = lip;
+	} else {
+		bp->b_fspriv = lip;
+	}
+
+	ASSERT(bp->b_iodone == NULL ||
+	       bp->b_iodone == xfs_buf_iodone_callbacks);
+	bp->b_iodone = xfs_buf_iodone_callbacks;
+}
+
+/*
+ * We can have many callbacks on a buffer. Running the callbacks individually
+ * can cause a lot of contention on the AIL lock, so we allow for a single
+ * callback to be able to scan the remaining lip->li_bio_list for other items
+ * of the same type and callback to be processed in the first call.
+ *
+ * As a result, the loop walking the callback list below will also modify the
+ * list. it removes the first item from the list and then runs the callback.
+ * The loop then restarts from the new head of the list. This allows the
+ * callback to scan and modify the list attached to the buffer and we don't
+ * have to care about maintaining a next item pointer.
+ */
+STATIC void
+xfs_buf_do_callbacks(
+	struct xfs_buf		*bp)
+{
+	struct xfs_log_item	*lip;
+
+	while ((lip = bp->b_fspriv) != NULL) {
+		bp->b_fspriv = 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);
+	}
+}
+
+/*
+ * 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(
+	struct xfs_buf		*bp)
+{
+	struct xfs_log_item	*lip = bp->b_fspriv;
+	struct xfs_mount	*mp = lip->li_mountp;
+	static ulong		lasttime;
+	static xfs_buftarg_t	*lasttarg;
+
+	if (likely(!xfs_buf_geterror(bp)))
+		goto do_callbacks;
+
+	/*
+	 * If we've already decided to shutdown the filesystem because of
+	 * I/O errors, there's no point in giving this a retry.
+	 */
+	if (XFS_FORCED_SHUTDOWN(mp)) {
+		xfs_buf_stale(bp);
+		XFS_BUF_DONE(bp);
+		trace_xfs_buf_item_iodone(bp, _RET_IP_);
+		goto do_callbacks;
+	}
+
+	if (bp->b_target != lasttarg ||
+	    time_after(jiffies, (lasttime + 5*HZ))) {
+		lasttime = jiffies;
+		xfs_buf_ioerror_alert(bp, __func__);
+	}
+	lasttarg = bp->b_target;
+
+	/*
+	 * If the write was asynchronous then no one will be looking for the
+	 * error.  Clear the error state and write the buffer out again.
+	 *
+	 * XXX: This helps against transient write errors, but we need to find
+	 * a way to shut the filesystem down if the writes keep failing.
+	 *
+	 * In practice we'll shut the filesystem down soon as non-transient
+	 * erorrs tend to affect the whole device and a failing log write
+	 * will make us give up.  But we really ought to do better here.
+	 */
+	if (XFS_BUF_ISASYNC(bp)) {
+		ASSERT(bp->b_iodone != NULL);
+
+		trace_xfs_buf_item_iodone_async(bp, _RET_IP_);
+
+		xfs_buf_ioerror(bp, 0); /* errno of 0 unsets the flag */
+
+		if (!XFS_BUF_ISSTALE(bp)) {
+			bp->b_flags |= XBF_WRITE | XBF_ASYNC | XBF_DONE;
+			xfs_buf_iorequest(bp);
+		} else {
+			xfs_buf_relse(bp);
+		}
+
+		return;
+	}
+
+	/*
+	 * If the write of the buffer was synchronous, we want to make
+	 * sure to return the error to the caller of xfs_bwrite().
+	 */
+	xfs_buf_stale(bp);
+	XFS_BUF_DONE(bp);
+
+	trace_xfs_buf_error_relse(bp, _RET_IP_);
+
+do_callbacks:
+	xfs_buf_do_callbacks(bp);
+	bp->b_fspriv = NULL;
+	bp->b_iodone = NULL;
+	xfs_buf_ioend(bp, 0);
+}
+
+/*
+ * 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.
+ */
+void
+xfs_buf_iodone(
+	struct xfs_buf		*bp,
+	struct xfs_log_item	*lip)
+{
+	struct xfs_ail		*ailp = lip->li_ailp;
+
+	ASSERT(BUF_ITEM(lip)->bli_buf == bp);
+
+	xfs_buf_rele(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.
+	 */
+	spin_lock(&ailp->xa_lock);
+	xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
+	xfs_buf_item_free(BUF_ITEM(lip));
+}