/*

   * 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_format.h"

  #include "xfs_log_format.h"
  #include "xfs_trans_resv.h"

  #include "xfs_bit.h"

  #include "xfs_sb.h"

  #include "xfs_mount.h"

  #include "xfs_trans.h"

  #include "xfs_buf_item.h"

  #include "xfs_trans_priv.h"

  #include "xfs_error.h"

  #include "xfs_trace.h"

  #include "xfs_log.h"

  #include "xfs_inode.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);

  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]));
  }

  /*
   * 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 void

  xfs_buf_item_size_segment(
  	struct xfs_buf_log_item	*bip,

  	struct xfs_buf_log_format *blfp,
  	int			*nvecs,
  	int			*nbytes)

  {

  	struct xfs_buf		*bp = bip->bli_buf;

  	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;

  
  	/*
  	 * initial count for a dirty buffer is 2 vectors - the format structure
  	 * and the first dirty region.
  	 */

  	*nvecs += 2;
  	*nbytes += xfs_buf_log_format_size(blfp) + XFS_BLF_CHUNK;

  	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++;
  		}

  		*nbytes += XFS_BLF_CHUNK;

  	}

  }
  
  /*

   * 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 void

  xfs_buf_item_size(

  	struct xfs_log_item	*lip,
  	int			*nvecs,
  	int			*nbytes)

  {

  	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);

  	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);

  		*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.
  	 */

  	for (i = 0; i < bip->bli_format_count; i++) {

  		xfs_buf_item_size_segment(bip, &bip->bli_formats[i],
  					  nvecs, nbytes);

  	}

  	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 inline bool
  xfs_buf_item_straddle(
  	struct xfs_buf		*bp,
  	uint			offset,
  	int			next_bit,
  	int			last_bit)
  {
  	return xfs_buf_offset(bp, offset + (next_bit << XFS_BLF_SHIFT)) !=
  		(xfs_buf_offset(bp, offset + (last_bit << XFS_BLF_SHIFT)) +
  		 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.
  	 */

  	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, next_bit, last_bit)) {

  			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_sb_version_hascrc(&lip->li_mountp->m_sb) ||
  		    !((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().

   *
   * 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(bp->b_flags & XBF_STALE);

  		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);

  		bp->b_flags &= ~XBF_DONE;

  		xfs_buf_stale(bp);

  		xfs_buf_ioend(bp);

  	}
  }

  /*
   * Buffer IO error rate limiting. Limit it to no more than 10 messages per 30
   * seconds so as to not spam logs too much on repeated detection of the same
   * buffer being bad..
   */

  static DEFINE_RATELIMIT_STATE(xfs_buf_write_fail_rl_state, 30 * HZ, 10);

  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) &&

  	    ___ratelimit(&xfs_buf_write_fail_rl_state, "XFS: Failing async write")) {

  		xfs_warn(bp->b_target->bt_mount,

  "Failing async write on buffer block 0x%llx. Retrying async write.",

  			 (long long)bp->b_bn);
  	}

  	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;

  	bool			aborted = !!(lip->li_flags & XFS_LI_ABORTED);
  	bool			hold = !!(bip->bli_flags & XFS_BLI_HOLD);
  	bool			dirty = !!(bip->bli_flags & XFS_BLI_DIRTY);

  #if defined(DEBUG) || defined(XFS_WARN)

  	bool			ordered = !!(bip->bli_flags & XFS_BLI_ORDERED);

  #endif

  	/* Clear the buffer's association with this transaction. */

  	bp->b_transp = NULL;

  
  	/*

  	 * The per-transaction state has been copied above so clear it from the
  	 * bli.

  	 */

  	bip->bli_flags &= ~(XFS_BLI_LOGGED | XFS_BLI_HOLD | XFS_BLI_ORDERED);

  
  	/*
  	 * 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.

  	 *

  	 * 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)));

  
  	/*
  	 * Clean buffers, by definition, cannot be in the AIL. However, aborted

  	 * buffers may be in the AIL regardless of dirty state. An aborted
  	 * transaction that invalidates a buffer already in the AIL may have
  	 * marked it stale and cleared the dirty state, for example.
  	 *
  	 * Therefore if we are aborting a buffer and we've just taken the last
  	 * reference away, we have to check if it is in the AIL before freeing
  	 * it. We need to free it in this case, because an aborted transaction
  	 * has already shut the filesystem down and this is the last chance we
  	 * will have to do so.

  	 */
  	if (atomic_dec_and_test(&bip->bli_refcount)) {

  		if (aborted) {

  			ASSERT(XFS_FORCED_SHUTDOWN(lip->li_mountp));

  			xfs_trans_ail_remove(lip, SHUTDOWN_LOG_IO_ERROR);

  			xfs_buf_item_relse(bp);

  		} else if (!dirty)

  			xfs_buf_item_relse(bp);

  	}

  	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.
   */

  int

  xfs_buf_item_init(

  	struct xfs_buf	*bp,
  	struct xfs_mount *mp)

  {

  	struct xfs_log_item	*lip = bp->b_fspriv;
  	struct xfs_buf_log_item	*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 0;

  	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;

  
  	/*
  	 * 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);

  	if (error) {	/* to stop gcc throwing set-but-unused warnings */
  		kmem_zone_free(xfs_buf_item_zone, bip);
  		return error;
  	}

  
  	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;
  	}

  	/*
  	 * 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;

  	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;
  
  	/*

  	 * 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(
  	xfs_buf_log_item_t	*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(
  	xfs_buf_log_item_t	*bip)
  {

  	xfs_buf_item_free_format(bip);

  	kmem_free(bip->bli_item.li_lv_shadow);

  	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 = bp->b_fspriv;

  	trace_xfs_buf_item_relse(bp, _RET_IP_);

  	ASSERT(!(bip->bli_item.li_flags & XFS_LI_IN_AIL));

  	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);

  	}
  }

  /*
   * Invoke the error state callback for each log item affected by the failed I/O.
   *
   * If a metadata buffer write fails with a non-permanent error, the buffer is
   * eventually resubmitted and so the completion callbacks are not run. The error
   * state may need to be propagated to the log items attached to the buffer,
   * however, so the next AIL push of the item knows hot to handle it correctly.
   */
  STATIC void
  xfs_buf_do_callbacks_fail(
  	struct xfs_buf		*bp)
  {
  	struct xfs_log_item	*next;
  	struct xfs_log_item	*lip = bp->b_fspriv;
  	struct xfs_ail		*ailp = lip->li_ailp;
  
  	spin_lock(&ailp->xa_lock);
  	for (; lip; lip = next) {
  		next = lip->li_bio_list;
  		if (lip->li_ops->iop_error)
  			lip->li_ops->iop_error(lip, bp);
  	}
  	spin_unlock(&ailp->xa_lock);
  }

  static bool
  xfs_buf_iodone_callback_error(

  	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;

  	struct xfs_error_cfg	*cfg;

  	/*
  	 * 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))
  		goto out_stale;

  	if (bp->b_target != lasttarg ||

  	    time_after(jiffies, (lasttime + 5*HZ))) {
  		lasttime = jiffies;

  		xfs_buf_ioerror_alert(bp, __func__);

  	}

  	lasttarg = bp->b_target;

  	/* synchronous writes will have callers process the error */
  	if (!(bp->b_flags & XBF_ASYNC))
  		goto out_stale;
  
  	trace_xfs_buf_item_iodone_async(bp, _RET_IP_);
  	ASSERT(bp->b_iodone != NULL);

  	cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);

  	/*

  	 * If the write was asynchronous then no one will be looking for the

  	 * error.  If this is the first failure of this type, clear the error
  	 * state and write the buffer out again. This means we always retry an
  	 * async write failure at least once, but we also need to set the buffer
  	 * up to behave correctly now for repeated failures.

  	 */

  	if (!(bp->b_flags & (XBF_STALE | XBF_WRITE_FAIL)) ||

  	     bp->b_last_error != bp->b_error) {

  		bp->b_flags |= (XBF_WRITE | XBF_DONE | XBF_WRITE_FAIL);

  		bp->b_last_error = bp->b_error;

  		if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&
  		    !bp->b_first_retry_time)

  			bp->b_first_retry_time = jiffies;

  		xfs_buf_ioerror(bp, 0);
  		xfs_buf_submit(bp);
  		return true;
  	}

  	/*
  	 * Repeated failure on an async write. Take action according to the
  	 * error configuration we have been set up to use.
  	 */

  
  	if (cfg->max_retries != XFS_ERR_RETRY_FOREVER &&
  	    ++bp->b_retries > cfg->max_retries)
  			goto permanent_error;

  	if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&

  	    time_after(jiffies, cfg->retry_timeout + bp->b_first_retry_time))
  			goto permanent_error;

  	/* At unmount we may treat errors differently */
  	if ((mp->m_flags & XFS_MOUNT_UNMOUNTING) && mp->m_fail_unmount)
  		goto permanent_error;

  	/*
  	 * Still a transient error, run IO completion failure callbacks and let
  	 * the higher layers retry the buffer.
  	 */
  	xfs_buf_do_callbacks_fail(bp);

  	xfs_buf_ioerror(bp, 0);
  	xfs_buf_relse(bp);
  	return true;

  	/*

  	 * Permanent error - we need to trigger a shutdown if we haven't already
  	 * to indicate that inconsistency will result from this action.

  	 */

  permanent_error:
  	xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
  out_stale:

  	xfs_buf_stale(bp);

  	bp->b_flags |= XBF_DONE;

  	trace_xfs_buf_error_relse(bp, _RET_IP_);

  	return false;
  }
  
  /*
   * This is the iodone() function for buffers which have had callbacks attached
   * to them by xfs_buf_attach_iodone(). We need to iterate the items on the
   * callback list, mark the buffer as having no more callbacks and then push the
   * buffer through IO completion processing.
   */
  void
  xfs_buf_iodone_callbacks(
  	struct xfs_buf		*bp)
  {
  	/*
  	 * If there is an error, process it. Some errors require us
  	 * to run callbacks after failure processing is done so we
  	 * detect that and take appropriate action.
  	 */
  	if (bp->b_error && xfs_buf_iodone_callback_error(bp))
  		return;
  
  	/*
  	 * Successful IO or permanent error. Either way, we can clear the
  	 * retry state here in preparation for the next error that may occur.
  	 */
  	bp->b_last_error = 0;

  	bp->b_retries = 0;

  	bp->b_first_retry_time = 0;

  	xfs_buf_do_callbacks(bp);

  	bp->b_fspriv = NULL;

  	bp->b_iodone = NULL;

  	xfs_buf_ioend(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.
   */

  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));

  }

  
  /*
   * Requeue a failed buffer for writeback
   *
   * Return true if the buffer has been re-queued properly, false otherwise
   */
  bool
  xfs_buf_resubmit_failed_buffers(
  	struct xfs_buf		*bp,
  	struct xfs_log_item	*lip,
  	struct list_head	*buffer_list)
  {
  	struct xfs_log_item	*next;
  
  	/*
  	 * Clear XFS_LI_FAILED flag from all items before resubmit
  	 *
  	 * XFS_LI_FAILED set/clear is protected by xa_lock, caller  this
  	 * function already have it acquired
  	 */
  	for (; lip; lip = next) {
  		next = lip->li_bio_list;
  		xfs_clear_li_failed(lip);
  	}
  
  	/* Add this buffer back to the delayed write list */
  	return xfs_buf_delwri_queue(bp, buffer_list);
  }