init android origin source code

1 files changed, 3844 insertions, 0 deletions

diff --git a/ANDROID_3.4.5/fs/xfs/xfs_log_recover.c b/ANDROID_3.4.5/fs/xfs/xfs_log_recover.c
new file mode 100644
index 00000000..8ecad5ba
--- /dev/null
+++ b/ANDROID_3.4.5/fs/xfs/xfs_log_recover.c
@@ -0,0 +1,3844 @@
+/*
+ * Copyright (c) 2000-2006 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_types.h"
+#include "xfs_bit.h"
+#include "xfs_log.h"
+#include "xfs_inum.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_ag.h"
+#include "xfs_mount.h"
+#include "xfs_error.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_dinode.h"
+#include "xfs_inode.h"
+#include "xfs_inode_item.h"
+#include "xfs_alloc.h"
+#include "xfs_ialloc.h"
+#include "xfs_log_priv.h"
+#include "xfs_buf_item.h"
+#include "xfs_log_recover.h"
+#include "xfs_extfree_item.h"
+#include "xfs_trans_priv.h"
+#include "xfs_quota.h"
+#include "xfs_rw.h"
+#include "xfs_utils.h"
+#include "xfs_trace.h"
+
+STATIC int	xlog_find_zeroed(xlog_t *, xfs_daddr_t *);
+STATIC int	xlog_clear_stale_blocks(xlog_t *, xfs_lsn_t);
+#if defined(DEBUG)
+STATIC void	xlog_recover_check_summary(xlog_t *);
+#else
+#define	xlog_recover_check_summary(log)
+#endif
+
+/*
+ * This structure is used during recovery to record the buf log items which
+ * have been canceled and should not be replayed.
+ */
+struct xfs_buf_cancel {
+	xfs_daddr_t		bc_blkno;
+	uint			bc_len;
+	int			bc_refcount;
+	struct list_head	bc_list;
+};
+
+/*
+ * Sector aligned buffer routines for buffer create/read/write/access
+ */
+
+/*
+ * Verify the given count of basic blocks is valid number of blocks
+ * to specify for an operation involving the given XFS log buffer.
+ * Returns nonzero if the count is valid, 0 otherwise.
+ */
+
+static inline int
+xlog_buf_bbcount_valid(
+	xlog_t		*log,
+	int		bbcount)
+{
+	return bbcount > 0 && bbcount <= log->l_logBBsize;
+}
+
+/*
+ * Allocate a buffer to hold log data.  The buffer needs to be able
+ * to map to a range of nbblks basic blocks at any valid (basic
+ * block) offset within the log.
+ */
+STATIC xfs_buf_t *
+xlog_get_bp(
+	xlog_t		*log,
+	int		nbblks)
+{
+	struct xfs_buf	*bp;
+
+	if (!xlog_buf_bbcount_valid(log, nbblks)) {
+		xfs_warn(log->l_mp, "Invalid block length (0x%x) for buffer",
+			nbblks);
+		XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_HIGH, log->l_mp);
+		return NULL;
+	}
+
+	/*
+	 * We do log I/O in units of log sectors (a power-of-2
+	 * multiple of the basic block size), so we round up the
+	 * requested size to accommodate the basic blocks required
+	 * for complete log sectors.
+	 *
+	 * In addition, the buffer may be used for a non-sector-
+	 * aligned block offset, in which case an I/O of the
+	 * requested size could extend beyond the end of the
+	 * buffer.  If the requested size is only 1 basic block it
+	 * will never straddle a sector boundary, so this won't be
+	 * an issue.  Nor will this be a problem if the log I/O is
+	 * done in basic blocks (sector size 1).  But otherwise we
+	 * extend the buffer by one extra log sector to ensure
+	 * there's space to accommodate this possibility.
+	 */
+	if (nbblks > 1 && log->l_sectBBsize > 1)
+		nbblks += log->l_sectBBsize;
+	nbblks = round_up(nbblks, log->l_sectBBsize);
+
+	bp = xfs_buf_get_uncached(log->l_mp->m_logdev_targp, BBTOB(nbblks), 0);
+	if (bp)
+		xfs_buf_unlock(bp);
+	return bp;
+}
+
+STATIC void
+xlog_put_bp(
+	xfs_buf_t	*bp)
+{
+	xfs_buf_free(bp);
+}
+
+/*
+ * Return the address of the start of the given block number's data
+ * in a log buffer.  The buffer covers a log sector-aligned region.
+ */
+STATIC xfs_caddr_t
+xlog_align(
+	xlog_t		*log,
+	xfs_daddr_t	blk_no,
+	int		nbblks,
+	xfs_buf_t	*bp)
+{
+	xfs_daddr_t	offset = blk_no & ((xfs_daddr_t)log->l_sectBBsize - 1);
+
+	ASSERT(BBTOB(offset + nbblks) <= XFS_BUF_SIZE(bp));
+	return bp->b_addr + BBTOB(offset);
+}
+
+
+/*
+ * nbblks should be uint, but oh well.  Just want to catch that 32-bit length.
+ */
+STATIC int
+xlog_bread_noalign(
+	xlog_t		*log,
+	xfs_daddr_t	blk_no,
+	int		nbblks,
+	xfs_buf_t	*bp)
+{
+	int		error;
+
+	if (!xlog_buf_bbcount_valid(log, nbblks)) {
+		xfs_warn(log->l_mp, "Invalid block length (0x%x) for buffer",
+			nbblks);
+		XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_HIGH, log->l_mp);
+		return EFSCORRUPTED;
+	}
+
+	blk_no = round_down(blk_no, log->l_sectBBsize);
+	nbblks = round_up(nbblks, log->l_sectBBsize);
+
+	ASSERT(nbblks > 0);
+	ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));
+
+	XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
+	XFS_BUF_READ(bp);
+	XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+
+	xfsbdstrat(log->l_mp, bp);
+	error = xfs_buf_iowait(bp);
+	if (error)
+		xfs_buf_ioerror_alert(bp, __func__);
+	return error;
+}
+
+STATIC int
+xlog_bread(
+	xlog_t		*log,
+	xfs_daddr_t	blk_no,
+	int		nbblks,
+	xfs_buf_t	*bp,
+	xfs_caddr_t	*offset)
+{
+	int		error;
+
+	error = xlog_bread_noalign(log, blk_no, nbblks, bp);
+	if (error)
+		return error;
+
+	*offset = xlog_align(log, blk_no, nbblks, bp);
+	return 0;
+}
+
+/*
+ * Read at an offset into the buffer. Returns with the buffer in it's original
+ * state regardless of the result of the read.
+ */
+STATIC int
+xlog_bread_offset(
+	xlog_t		*log,
+	xfs_daddr_t	blk_no,		/* block to read from */
+	int		nbblks,		/* blocks to read */
+	xfs_buf_t	*bp,
+	xfs_caddr_t	offset)
+{
+	xfs_caddr_t	orig_offset = bp->b_addr;
+	int		orig_len = bp->b_buffer_length;
+	int		error, error2;
+
+	error = xfs_buf_associate_memory(bp, offset, BBTOB(nbblks));
+	if (error)
+		return error;
+
+	error = xlog_bread_noalign(log, blk_no, nbblks, bp);
+
+	/* must reset buffer pointer even on error */
+	error2 = xfs_buf_associate_memory(bp, orig_offset, orig_len);
+	if (error)
+		return error;
+	return error2;
+}
+
+/*
+ * Write out the buffer at the given block for the given number of blocks.
+ * The buffer is kept locked across the write and is returned locked.
+ * This can only be used for synchronous log writes.
+ */
+STATIC int
+xlog_bwrite(
+	xlog_t		*log,
+	xfs_daddr_t	blk_no,
+	int		nbblks,
+	xfs_buf_t	*bp)
+{
+	int		error;
+
+	if (!xlog_buf_bbcount_valid(log, nbblks)) {
+		xfs_warn(log->l_mp, "Invalid block length (0x%x) for buffer",
+			nbblks);
+		XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_HIGH, log->l_mp);
+		return EFSCORRUPTED;
+	}
+
+	blk_no = round_down(blk_no, log->l_sectBBsize);
+	nbblks = round_up(nbblks, log->l_sectBBsize);
+
+	ASSERT(nbblks > 0);
+	ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));
+
+	XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
+	XFS_BUF_ZEROFLAGS(bp);
+	xfs_buf_hold(bp);
+	xfs_buf_lock(bp);
+	XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+
+	error = xfs_bwrite(bp);
+	if (error)
+		xfs_buf_ioerror_alert(bp, __func__);
+	xfs_buf_relse(bp);
+	return error;
+}
+
+#ifdef DEBUG
+/*
+ * dump debug superblock and log record information
+ */
+STATIC void
+xlog_header_check_dump(
+	xfs_mount_t		*mp,
+	xlog_rec_header_t	*head)
+{
+	xfs_debug(mp, "%s:  SB : uuid = %pU, fmt = %d\n",
+		__func__, &mp->m_sb.sb_uuid, XLOG_FMT);
+	xfs_debug(mp, "    log : uuid = %pU, fmt = %d\n",
+		&head->h_fs_uuid, be32_to_cpu(head->h_fmt));
+}
+#else
+#define xlog_header_check_dump(mp, head)
+#endif
+
+/*
+ * check log record header for recovery
+ */
+STATIC int
+xlog_header_check_recover(
+	xfs_mount_t		*mp,
+	xlog_rec_header_t	*head)
+{
+	ASSERT(head->h_magicno == cpu_to_be32(XLOG_HEADER_MAGIC_NUM));
+
+	/*
+	 * IRIX doesn't write the h_fmt field and leaves it zeroed
+	 * (XLOG_FMT_UNKNOWN). This stops us from trying to recover
+	 * a dirty log created in IRIX.
+	 */
+	if (unlikely(head->h_fmt != cpu_to_be32(XLOG_FMT))) {
+		xfs_warn(mp,
+	"dirty log written in incompatible format - can't recover");
+		xlog_header_check_dump(mp, head);
+		XFS_ERROR_REPORT("xlog_header_check_recover(1)",
+				 XFS_ERRLEVEL_HIGH, mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	} else if (unlikely(!uuid_equal(&mp->m_sb.sb_uuid, &head->h_fs_uuid))) {
+		xfs_warn(mp,
+	"dirty log entry has mismatched uuid - can't recover");
+		xlog_header_check_dump(mp, head);
+		XFS_ERROR_REPORT("xlog_header_check_recover(2)",
+				 XFS_ERRLEVEL_HIGH, mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	return 0;
+}
+
+/*
+ * read the head block of the log and check the header
+ */
+STATIC int
+xlog_header_check_mount(
+	xfs_mount_t		*mp,
+	xlog_rec_header_t	*head)
+{
+	ASSERT(head->h_magicno == cpu_to_be32(XLOG_HEADER_MAGIC_NUM));
+
+	if (uuid_is_nil(&head->h_fs_uuid)) {
+		/*
+		 * IRIX doesn't write the h_fs_uuid or h_fmt fields. If
+		 * h_fs_uuid is nil, we assume this log was last mounted
+		 * by IRIX and continue.
+		 */
+		xfs_warn(mp, "nil uuid in log - IRIX style log");
+	} else if (unlikely(!uuid_equal(&mp->m_sb.sb_uuid, &head->h_fs_uuid))) {
+		xfs_warn(mp, "log has mismatched uuid - can't recover");
+		xlog_header_check_dump(mp, head);
+		XFS_ERROR_REPORT("xlog_header_check_mount",
+				 XFS_ERRLEVEL_HIGH, mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	return 0;
+}
+
+STATIC void
+xlog_recover_iodone(
+	struct xfs_buf	*bp)
+{
+	if (bp->b_error) {
+		/*
+		 * We're not going to bother about retrying
+		 * this during recovery. One strike!
+		 */
+		xfs_buf_ioerror_alert(bp, __func__);
+		xfs_force_shutdown(bp->b_target->bt_mount,
+					SHUTDOWN_META_IO_ERROR);
+	}
+	bp->b_iodone = NULL;
+	xfs_buf_ioend(bp, 0);
+}
+
+/*
+ * This routine finds (to an approximation) the first block in the physical
+ * log which contains the given cycle.  It uses a binary search algorithm.
+ * Note that the algorithm can not be perfect because the disk will not
+ * necessarily be perfect.
+ */
+STATIC int
+xlog_find_cycle_start(
+	xlog_t		*log,
+	xfs_buf_t	*bp,
+	xfs_daddr_t	first_blk,
+	xfs_daddr_t	*last_blk,
+	uint		cycle)
+{
+	xfs_caddr_t	offset;
+	xfs_daddr_t	mid_blk;
+	xfs_daddr_t	end_blk;
+	uint		mid_cycle;
+	int		error;
+
+	end_blk = *last_blk;
+	mid_blk = BLK_AVG(first_blk, end_blk);
+	while (mid_blk != first_blk && mid_blk != end_blk) {
+		error = xlog_bread(log, mid_blk, 1, bp, &offset);
+		if (error)
+			return error;
+		mid_cycle = xlog_get_cycle(offset);
+		if (mid_cycle == cycle)
+			end_blk = mid_blk;   /* last_half_cycle == mid_cycle */
+		else
+			first_blk = mid_blk; /* first_half_cycle == mid_cycle */
+		mid_blk = BLK_AVG(first_blk, end_blk);
+	}
+	ASSERT((mid_blk == first_blk && mid_blk+1 == end_blk) ||
+	       (mid_blk == end_blk && mid_blk-1 == first_blk));
+
+	*last_blk = end_blk;
+
+	return 0;
+}
+
+/*
+ * Check that a range of blocks does not contain stop_on_cycle_no.
+ * Fill in *new_blk with the block offset where such a block is
+ * found, or with -1 (an invalid block number) if there is no such
+ * block in the range.  The scan needs to occur from front to back
+ * and the pointer into the region must be updated since a later
+ * routine will need to perform another test.
+ */
+STATIC int
+xlog_find_verify_cycle(
+	xlog_t		*log,
+	xfs_daddr_t	start_blk,
+	int		nbblks,
+	uint		stop_on_cycle_no,
+	xfs_daddr_t	*new_blk)
+{
+	xfs_daddr_t	i, j;
+	uint		cycle;
+	xfs_buf_t	*bp;
+	xfs_daddr_t	bufblks;
+	xfs_caddr_t	buf = NULL;
+	int		error = 0;
+
+	/*
+	 * Greedily allocate a buffer big enough to handle the full
+	 * range of basic blocks we'll be examining.  If that fails,
+	 * try a smaller size.  We need to be able to read at least
+	 * a log sector, or we're out of luck.
+	 */
+	bufblks = 1 << ffs(nbblks);
+	while (!(bp = xlog_get_bp(log, bufblks))) {
+		bufblks >>= 1;
+		if (bufblks < log->l_sectBBsize)
+			return ENOMEM;
+	}
+
+	for (i = start_blk; i < start_blk + nbblks; i += bufblks) {
+		int	bcount;
+
+		bcount = min(bufblks, (start_blk + nbblks - i));
+
+		error = xlog_bread(log, i, bcount, bp, &buf);
+		if (error)
+			goto out;
+
+		for (j = 0; j < bcount; j++) {
+			cycle = xlog_get_cycle(buf);
+			if (cycle == stop_on_cycle_no) {
+				*new_blk = i+j;
+				goto out;
+			}
+
+			buf += BBSIZE;
+		}
+	}
+
+	*new_blk = -1;
+
+out:
+	xlog_put_bp(bp);
+	return error;
+}
+
+/*
+ * Potentially backup over partial log record write.
+ *
+ * In the typical case, last_blk is the number of the block directly after
+ * a good log record.  Therefore, we subtract one to get the block number
+ * of the last block in the given buffer.  extra_bblks contains the number
+ * of blocks we would have read on a previous read.  This happens when the
+ * last log record is split over the end of the physical log.
+ *
+ * extra_bblks is the number of blocks potentially verified on a previous
+ * call to this routine.
+ */
+STATIC int
+xlog_find_verify_log_record(
+	xlog_t			*log,
+	xfs_daddr_t		start_blk,
+	xfs_daddr_t		*last_blk,
+	int			extra_bblks)
+{
+	xfs_daddr_t		i;
+	xfs_buf_t		*bp;
+	xfs_caddr_t		offset = NULL;
+	xlog_rec_header_t	*head = NULL;
+	int			error = 0;
+	int			smallmem = 0;
+	int			num_blks = *last_blk - start_blk;
+	int			xhdrs;
+
+	ASSERT(start_blk != 0 || *last_blk != start_blk);
+
+	if (!(bp = xlog_get_bp(log, num_blks))) {
+		if (!(bp = xlog_get_bp(log, 1)))
+			return ENOMEM;
+		smallmem = 1;
+	} else {
+		error = xlog_bread(log, start_blk, num_blks, bp, &offset);
+		if (error)
+			goto out;
+		offset += ((num_blks - 1) << BBSHIFT);
+	}
+
+	for (i = (*last_blk) - 1; i >= 0; i--) {
+		if (i < start_blk) {
+			/* valid log record not found */
+			xfs_warn(log->l_mp,
+		"Log inconsistent (didn't find previous header)");
+			ASSERT(0);
+			error = XFS_ERROR(EIO);
+			goto out;
+		}
+
+		if (smallmem) {
+			error = xlog_bread(log, i, 1, bp, &offset);
+			if (error)
+				goto out;
+		}
+
+		head = (xlog_rec_header_t *)offset;
+
+		if (head->h_magicno == cpu_to_be32(XLOG_HEADER_MAGIC_NUM))
+			break;
+
+		if (!smallmem)
+			offset -= BBSIZE;
+	}
+
+	/*
+	 * We hit the beginning of the physical log & still no header.  Return
+	 * to caller.  If caller can handle a return of -1, then this routine
+	 * will be called again for the end of the physical log.
+	 */
+	if (i == -1) {
+		error = -1;
+		goto out;
+	}
+
+	/*
+	 * We have the final block of the good log (the first block
+	 * of the log record _before_ the head. So we check the uuid.
+	 */
+	if ((error = xlog_header_check_mount(log->l_mp, head)))
+		goto out;
+
+	/*
+	 * We may have found a log record header before we expected one.
+	 * last_blk will be the 1st block # with a given cycle #.  We may end
+	 * up reading an entire log record.  In this case, we don't want to
+	 * reset last_blk.  Only when last_blk points in the middle of a log
+	 * record do we update last_blk.
+	 */
+	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
+		uint	h_size = be32_to_cpu(head->h_size);
+
+		xhdrs = h_size / XLOG_HEADER_CYCLE_SIZE;
+		if (h_size % XLOG_HEADER_CYCLE_SIZE)
+			xhdrs++;
+	} else {
+		xhdrs = 1;
+	}
+
+	if (*last_blk - i + extra_bblks !=
+	    BTOBB(be32_to_cpu(head->h_len)) + xhdrs)
+		*last_blk = i;
+
+out:
+	xlog_put_bp(bp);
+	return error;
+}
+
+/*
+ * Head is defined to be the point of the log where the next log write
+ * write could go.  This means that incomplete LR writes at the end are
+ * eliminated when calculating the head.  We aren't guaranteed that previous
+ * LR have complete transactions.  We only know that a cycle number of
+ * current cycle number -1 won't be present in the log if we start writing
+ * from our current block number.
+ *
+ * last_blk contains the block number of the first block with a given
+ * cycle number.
+ *
+ * Return: zero if normal, non-zero if error.
+ */
+STATIC int
+xlog_find_head(
+	xlog_t 		*log,
+	xfs_daddr_t	*return_head_blk)
+{
+	xfs_buf_t	*bp;
+	xfs_caddr_t	offset;
+	xfs_daddr_t	new_blk, first_blk, start_blk, last_blk, head_blk;
+	int		num_scan_bblks;
+	uint		first_half_cycle, last_half_cycle;
+	uint		stop_on_cycle;
+	int		error, log_bbnum = log->l_logBBsize;
+
+	/* Is the end of the log device zeroed? */
+	if ((error = xlog_find_zeroed(log, &first_blk)) == -1) {
+		*return_head_blk = first_blk;
+
+		/* Is the whole lot zeroed? */
+		if (!first_blk) {
+			/* Linux XFS shouldn't generate totally zeroed logs -
+			 * mkfs etc write a dummy unmount record to a fresh
+			 * log so we can store the uuid in there
+			 */
+			xfs_warn(log->l_mp, "totally zeroed log");
+		}
+
+		return 0;
+	} else if (error) {
+		xfs_warn(log->l_mp, "empty log check failed");
+		return error;
+	}
+
+	first_blk = 0;			/* get cycle # of 1st block */
+	bp = xlog_get_bp(log, 1);
+	if (!bp)
+		return ENOMEM;
+
+	error = xlog_bread(log, 0, 1, bp, &offset);
+	if (error)
+		goto bp_err;
+
+	first_half_cycle = xlog_get_cycle(offset);
+
+	last_blk = head_blk = log_bbnum - 1;	/* get cycle # of last block */
+	error = xlog_bread(log, last_blk, 1, bp, &offset);
+	if (error)
+		goto bp_err;
+
+	last_half_cycle = xlog_get_cycle(offset);
+	ASSERT(last_half_cycle != 0);
+
+	/*
+	 * If the 1st half cycle number is equal to the last half cycle number,
+	 * then the entire log is stamped with the same cycle number.  In this
+	 * case, head_blk can't be set to zero (which makes sense).  The below
+	 * math doesn't work out properly with head_blk equal to zero.  Instead,
+	 * we set it to log_bbnum which is an invalid block number, but this
+	 * value makes the math correct.  If head_blk doesn't changed through
+	 * all the tests below, *head_blk is set to zero at the very end rather
+	 * than log_bbnum.  In a sense, log_bbnum and zero are the same block
+	 * in a circular file.
+	 */
+	if (first_half_cycle == last_half_cycle) {
+		/*
+		 * In this case we believe that the entire log should have
+		 * cycle number last_half_cycle.  We need to scan backwards
+		 * from the end verifying that there are no holes still
+		 * containing last_half_cycle - 1.  If we find such a hole,
+		 * then the start of that hole will be the new head.  The
+		 * simple case looks like
+		 *        x | x ... | x - 1 | x
+		 * Another case that fits this picture would be
+		 *        x | x + 1 | x ... | x
+		 * In this case the head really is somewhere at the end of the
+		 * log, as one of the latest writes at the beginning was
+		 * incomplete.
+		 * One more case is
+		 *        x | x + 1 | x ... | x - 1 | x
+		 * This is really the combination of the above two cases, and
+		 * the head has to end up at the start of the x-1 hole at the
+		 * end of the log.
+		 *
+		 * In the 256k log case, we will read from the beginning to the
+		 * end of the log and search for cycle numbers equal to x-1.
+		 * We don't worry about the x+1 blocks that we encounter,
+		 * because we know that they cannot be the head since the log
+		 * started with x.
+		 */
+		head_blk = log_bbnum;
+		stop_on_cycle = last_half_cycle - 1;
+	} else {
+		/*
+		 * In this case we want to find the first block with cycle
+		 * number matching last_half_cycle.  We expect the log to be
+		 * some variation on
+		 *        x + 1 ... | x ... | x
+		 * The first block with cycle number x (last_half_cycle) will
+		 * be where the new head belongs.  First we do a binary search
+		 * for the first occurrence of last_half_cycle.  The binary
+		 * search may not be totally accurate, so then we scan back
+		 * from there looking for occurrences of last_half_cycle before
+		 * us.  If that backwards scan wraps around the beginning of
+		 * the log, then we look for occurrences of last_half_cycle - 1
+		 * at the end of the log.  The cases we're looking for look
+		 * like
+		 *                               v binary search stopped here
+		 *        x + 1 ... | x | x + 1 | x ... | x
+		 *                   ^ but we want to locate this spot
+		 * or
+		 *        <---------> less than scan distance
+		 *        x + 1 ... | x ... | x - 1 | x
+		 *                           ^ we want to locate this spot
+		 */
+		stop_on_cycle = last_half_cycle;
+		if ((error = xlog_find_cycle_start(log, bp, first_blk,
+						&head_blk, last_half_cycle)))
+			goto bp_err;
+	}
+
+	/*
+	 * Now validate the answer.  Scan back some number of maximum possible
+	 * blocks and make sure each one has the expected cycle number.  The
+	 * maximum is determined by the total possible amount of buffering
+	 * in the in-core log.  The following number can be made tighter if
+	 * we actually look at the block size of the filesystem.
+	 */
+	num_scan_bblks = XLOG_TOTAL_REC_SHIFT(log);
+	if (head_blk >= num_scan_bblks) {
+		/*
+		 * We are guaranteed that the entire check can be performed
+		 * in one buffer.
+		 */
+		start_blk = head_blk - num_scan_bblks;
+		if ((error = xlog_find_verify_cycle(log,
+						start_blk, num_scan_bblks,
+						stop_on_cycle, &new_blk)))
+			goto bp_err;
+		if (new_blk != -1)
+			head_blk = new_blk;
+	} else {		/* need to read 2 parts of log */
+		/*
+		 * We are going to scan backwards in the log in two parts.
+		 * First we scan the physical end of the log.  In this part
+		 * of the log, we are looking for blocks with cycle number
+		 * last_half_cycle - 1.
+		 * If we find one, then we know that the log starts there, as
+		 * we've found a hole that didn't get written in going around
+		 * the end of the physical log.  The simple case for this is
+		 *        x + 1 ... | x ... | x - 1 | x
+		 *        <---------> less than scan distance
+		 * If all of the blocks at the end of the log have cycle number
+		 * last_half_cycle, then we check the blocks at the start of
+		 * the log looking for occurrences of last_half_cycle.  If we
+		 * find one, then our current estimate for the location of the
+		 * first occurrence of last_half_cycle is wrong and we move
+		 * back to the hole we've found.  This case looks like
+		 *        x + 1 ... | x | x + 1 | x ...
+		 *                               ^ binary search stopped here
+		 * Another case we need to handle that only occurs in 256k
+		 * logs is
+		 *        x + 1 ... | x ... | x+1 | x ...
+		 *                   ^ binary search stops here
+		 * In a 256k log, the scan at the end of the log will see the
+		 * x + 1 blocks.  We need to skip past those since that is
+		 * certainly not the head of the log.  By searching for
+		 * last_half_cycle-1 we accomplish that.
+		 */
+		ASSERT(head_blk <= INT_MAX &&
+			(xfs_daddr_t) num_scan_bblks >= head_blk);
+		start_blk = log_bbnum - (num_scan_bblks - head_blk);
+		if ((error = xlog_find_verify_cycle(log, start_blk,
+					num_scan_bblks - (int)head_blk,
+					(stop_on_cycle - 1), &new_blk)))
+			goto bp_err;
+		if (new_blk != -1) {
+			head_blk = new_blk;
+			goto validate_head;
+		}
+
+		/*
+		 * Scan beginning of log now.  The last part of the physical
+		 * log is good.  This scan needs to verify that it doesn't find
+		 * the last_half_cycle.
+		 */
+		start_blk = 0;
+		ASSERT(head_blk <= INT_MAX);
+		if ((error = xlog_find_verify_cycle(log,
+					start_blk, (int)head_blk,
+					stop_on_cycle, &new_blk)))
+			goto bp_err;
+		if (new_blk != -1)
+			head_blk = new_blk;
+	}
+
+validate_head:
+	/*
+	 * Now we need to make sure head_blk is not pointing to a block in
+	 * the middle of a log record.
+	 */
+	num_scan_bblks = XLOG_REC_SHIFT(log);
+	if (head_blk >= num_scan_bblks) {
+		start_blk = head_blk - num_scan_bblks; /* don't read head_blk */
+
+		/* start ptr at last block ptr before head_blk */
+		if ((error = xlog_find_verify_log_record(log, start_blk,
+							&head_blk, 0)) == -1) {
+			error = XFS_ERROR(EIO);
+			goto bp_err;
+		} else if (error)
+			goto bp_err;
+	} else {
+		start_blk = 0;
+		ASSERT(head_blk <= INT_MAX);
+		if ((error = xlog_find_verify_log_record(log, start_blk,
+							&head_blk, 0)) == -1) {
+			/* We hit the beginning of the log during our search */
+			start_blk = log_bbnum - (num_scan_bblks - head_blk);
+			new_blk = log_bbnum;
+			ASSERT(start_blk <= INT_MAX &&
+				(xfs_daddr_t) log_bbnum-start_blk >= 0);
+			ASSERT(head_blk <= INT_MAX);
+			if ((error = xlog_find_verify_log_record(log,
+							start_blk, &new_blk,
+							(int)head_blk)) == -1) {
+				error = XFS_ERROR(EIO);
+				goto bp_err;
+			} else if (error)
+				goto bp_err;
+			if (new_blk != log_bbnum)
+				head_blk = new_blk;
+		} else if (error)
+			goto bp_err;
+	}
+
+	xlog_put_bp(bp);
+	if (head_blk == log_bbnum)
+		*return_head_blk = 0;
+	else
+		*return_head_blk = head_blk;
+	/*
+	 * When returning here, we have a good block number.  Bad block
+	 * means that during a previous crash, we didn't have a clean break
+	 * from cycle number N to cycle number N-1.  In this case, we need
+	 * to find the first block with cycle number N-1.
+	 */
+	return 0;
+
+ bp_err:
+	xlog_put_bp(bp);
+
+	if (error)
+		xfs_warn(log->l_mp, "failed to find log head");
+	return error;
+}
+
+/*
+ * Find the sync block number or the tail of the log.
+ *
+ * This will be the block number of the last record to have its
+ * associated buffers synced to disk.  Every log record header has
+ * a sync lsn embedded in it.  LSNs hold block numbers, so it is easy
+ * to get a sync block number.  The only concern is to figure out which
+ * log record header to believe.
+ *
+ * The following algorithm uses the log record header with the largest
+ * lsn.  The entire log record does not need to be valid.  We only care
+ * that the header is valid.
+ *
+ * We could speed up search by using current head_blk buffer, but it is not
+ * available.
+ */
+STATIC int
+xlog_find_tail(
+	xlog_t			*log,
+	xfs_daddr_t		*head_blk,
+	xfs_daddr_t		*tail_blk)
+{
+	xlog_rec_header_t	*rhead;
+	xlog_op_header_t	*op_head;
+	xfs_caddr_t		offset = NULL;
+	xfs_buf_t		*bp;
+	int			error, i, found;
+	xfs_daddr_t		umount_data_blk;
+	xfs_daddr_t		after_umount_blk;
+	xfs_lsn_t		tail_lsn;
+	int			hblks;
+
+	found = 0;
+
+	/*
+	 * Find previous log record
+	 */
+	if ((error = xlog_find_head(log, head_blk)))
+		return error;
+
+	bp = xlog_get_bp(log, 1);
+	if (!bp)
+		return ENOMEM;
+	if (*head_blk == 0) {				/* special case */
+		error = xlog_bread(log, 0, 1, bp, &offset);
+		if (error)
+			goto done;
+
+		if (xlog_get_cycle(offset) == 0) {
+			*tail_blk = 0;
+			/* leave all other log inited values alone */
+			goto done;
+		}
+	}
+
+	/*
+	 * Search backwards looking for log record header block
+	 */
+	ASSERT(*head_blk < INT_MAX);
+	for (i = (int)(*head_blk) - 1; i >= 0; i--) {
+		error = xlog_bread(log, i, 1, bp, &offset);
+		if (error)
+			goto done;
+
+		if (*(__be32 *)offset == cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
+			found = 1;
+			break;
+		}
+	}
+	/*
+	 * If we haven't found the log record header block, start looking
+	 * again from the end of the physical log.  XXXmiken: There should be
+	 * a check here to make sure we didn't search more than N blocks in
+	 * the previous code.
+	 */
+	if (!found) {
+		for (i = log->l_logBBsize - 1; i >= (int)(*head_blk); i--) {
+			error = xlog_bread(log, i, 1, bp, &offset);
+			if (error)
+				goto done;
+
+			if (*(__be32 *)offset ==
+			    cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
+				found = 2;
+				break;
+			}
+		}
+	}
+	if (!found) {
+		xfs_warn(log->l_mp, "%s: couldn't find sync record", __func__);
+		ASSERT(0);
+		return XFS_ERROR(EIO);
+	}
+
+	/* find blk_no of tail of log */
+	rhead = (xlog_rec_header_t *)offset;
+	*tail_blk = BLOCK_LSN(be64_to_cpu(rhead->h_tail_lsn));
+
+	/*
+	 * Reset log values according to the state of the log when we
+	 * crashed.  In the case where head_blk == 0, we bump curr_cycle
+	 * one because the next write starts a new cycle rather than
+	 * continuing the cycle of the last good log record.  At this
+	 * point we have guaranteed that all partial log records have been
+	 * accounted for.  Therefore, we know that the last good log record
+	 * written was complete and ended exactly on the end boundary
+	 * of the physical log.
+	 */
+	log->l_prev_block = i;
+	log->l_curr_block = (int)*head_blk;
+	log->l_curr_cycle = be32_to_cpu(rhead->h_cycle);
+	if (found == 2)
+		log->l_curr_cycle++;
+	atomic64_set(&log->l_tail_lsn, be64_to_cpu(rhead->h_tail_lsn));
+	atomic64_set(&log->l_last_sync_lsn, be64_to_cpu(rhead->h_lsn));
+	xlog_assign_grant_head(&log->l_reserve_head.grant, log->l_curr_cycle,
+					BBTOB(log->l_curr_block));
+	xlog_assign_grant_head(&log->l_write_head.grant, log->l_curr_cycle,
+					BBTOB(log->l_curr_block));
+
+	/*
+	 * Look for unmount record.  If we find it, then we know there
+	 * was a clean unmount.  Since 'i' could be the last block in
+	 * the physical log, we convert to a log block before comparing
+	 * to the head_blk.
+	 *
+	 * Save the current tail lsn to use to pass to
+	 * xlog_clear_stale_blocks() below.  We won't want to clear the
+	 * unmount record if there is one, so we pass the lsn of the
+	 * unmount record rather than the block after it.
+	 */
+	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
+		int	h_size = be32_to_cpu(rhead->h_size);
+		int	h_version = be32_to_cpu(rhead->h_version);
+
+		if ((h_version & XLOG_VERSION_2) &&
+		    (h_size > XLOG_HEADER_CYCLE_SIZE)) {
+			hblks = h_size / XLOG_HEADER_CYCLE_SIZE;
+			if (h_size % XLOG_HEADER_CYCLE_SIZE)
+				hblks++;
+		} else {
+			hblks = 1;
+		}
+	} else {
+		hblks = 1;
+	}
+	after_umount_blk = (i + hblks + (int)
+		BTOBB(be32_to_cpu(rhead->h_len))) % log->l_logBBsize;
+	tail_lsn = atomic64_read(&log->l_tail_lsn);
+	if (*head_blk == after_umount_blk &&
+	    be32_to_cpu(rhead->h_num_logops) == 1) {
+		umount_data_blk = (i + hblks) % log->l_logBBsize;
+		error = xlog_bread(log, umount_data_blk, 1, bp, &offset);
+		if (error)
+			goto done;
+
+		op_head = (xlog_op_header_t *)offset;
+		if (op_head->oh_flags & XLOG_UNMOUNT_TRANS) {
+			/*
+			 * Set tail and last sync so that newly written
+			 * log records will point recovery to after the
+			 * current unmount record.
+			 */
+			xlog_assign_atomic_lsn(&log->l_tail_lsn,
+					log->l_curr_cycle, after_umount_blk);
+			xlog_assign_atomic_lsn(&log->l_last_sync_lsn,
+					log->l_curr_cycle, after_umount_blk);
+			*tail_blk = after_umount_blk;
+
+			/*
+			 * Note that the unmount was clean. If the unmount
+			 * was not clean, we need to know this to rebuild the
+			 * superblock counters from the perag headers if we
+			 * have a filesystem using non-persistent counters.
+			 */
+			log->l_mp->m_flags |= XFS_MOUNT_WAS_CLEAN;
+		}
+	}
+
+	/*
+	 * Make sure that there are no blocks in front of the head
+	 * with the same cycle number as the head.  This can happen
+	 * because we allow multiple outstanding log writes concurrently,
+	 * and the later writes might make it out before earlier ones.
+	 *
+	 * We use the lsn from before modifying it so that we'll never
+	 * overwrite the unmount record after a clean unmount.
+	 *
+	 * Do this only if we are going to recover the filesystem
+	 *
+	 * NOTE: This used to say "if (!readonly)"
+	 * However on Linux, we can & do recover a read-only filesystem.
+	 * We only skip recovery if NORECOVERY is specified on mount,
+	 * in which case we would not be here.
+	 *
+	 * But... if the -device- itself is readonly, just skip this.
+	 * We can't recover this device anyway, so it won't matter.
+	 */
+	if (!xfs_readonly_buftarg(log->l_mp->m_logdev_targp))
+		error = xlog_clear_stale_blocks(log, tail_lsn);
+
+done:
+	xlog_put_bp(bp);
+
+	if (error)
+		xfs_warn(log->l_mp, "failed to locate log tail");
+	return error;
+}
+
+/*
+ * Is the log zeroed at all?
+ *
+ * The last binary search should be changed to perform an X block read
+ * once X becomes small enough.  You can then search linearly through
+ * the X blocks.  This will cut down on the number of reads we need to do.
+ *
+ * If the log is partially zeroed, this routine will pass back the blkno
+ * of the first block with cycle number 0.  It won't have a complete LR
+ * preceding it.
+ *
+ * Return:
+ *	0  => the log is completely written to
+ *	-1 => use *blk_no as the first block of the log
+ *	>0 => error has occurred
+ */
+STATIC int
+xlog_find_zeroed(
+	xlog_t		*log,
+	xfs_daddr_t	*blk_no)
+{
+	xfs_buf_t	*bp;
+	xfs_caddr_t	offset;
+	uint	        first_cycle, last_cycle;
+	xfs_daddr_t	new_blk, last_blk, start_blk;
+	xfs_daddr_t     num_scan_bblks;
+	int	        error, log_bbnum = log->l_logBBsize;
+
+	*blk_no = 0;
+
+	/* check totally zeroed log */
+	bp = xlog_get_bp(log, 1);
+	if (!bp)
+		return ENOMEM;
+	error = xlog_bread(log, 0, 1, bp, &offset);
+	if (error)
+		goto bp_err;
+
+	first_cycle = xlog_get_cycle(offset);
+	if (first_cycle == 0) {		/* completely zeroed log */
+		*blk_no = 0;
+		xlog_put_bp(bp);
+		return -1;
+	}
+
+	/* check partially zeroed log */
+	error = xlog_bread(log, log_bbnum-1, 1, bp, &offset);
+	if (error)
+		goto bp_err;
+
+	last_cycle = xlog_get_cycle(offset);
+	if (last_cycle != 0) {		/* log completely written to */
+		xlog_put_bp(bp);
+		return 0;
+	} else if (first_cycle != 1) {
+		/*
+		 * If the cycle of the last block is zero, the cycle of
+		 * the first block must be 1. If it's not, maybe we're
+		 * not looking at a log... Bail out.
+		 */
+		xfs_warn(log->l_mp,
+			"Log inconsistent or not a log (last==0, first!=1)");
+		return XFS_ERROR(EINVAL);
+	}
+
+	/* we have a partially zeroed log */
+	last_blk = log_bbnum-1;
+	if ((error = xlog_find_cycle_start(log, bp, 0, &last_blk, 0)))
+		goto bp_err;
+
+	/*
+	 * Validate the answer.  Because there is no way to guarantee that
+	 * the entire log is made up of log records which are the same size,
+	 * we scan over the defined maximum blocks.  At this point, the maximum
+	 * is not chosen to mean anything special.   XXXmiken
+	 */
+	num_scan_bblks = XLOG_TOTAL_REC_SHIFT(log);
+	ASSERT(num_scan_bblks <= INT_MAX);
+
+	if (last_blk < num_scan_bblks)
+		num_scan_bblks = last_blk;
+	start_blk = last_blk - num_scan_bblks;
+
+	/*
+	 * We search for any instances of cycle number 0 that occur before
+	 * our current estimate of the head.  What we're trying to detect is
+	 *        1 ... | 0 | 1 | 0...
+	 *                       ^ binary search ends here
+	 */
+	if ((error = xlog_find_verify_cycle(log, start_blk,
+					 (int)num_scan_bblks, 0, &new_blk)))
+		goto bp_err;
+	if (new_blk != -1)
+		last_blk = new_blk;
+
+	/*
+	 * Potentially backup over partial log record write.  We don't need
+	 * to search the end of the log because we know it is zero.
+	 */
+	if ((error = xlog_find_verify_log_record(log, start_blk,
+				&last_blk, 0)) == -1) {
+	    error = XFS_ERROR(EIO);
+	    goto bp_err;
+	} else if (error)
+	    goto bp_err;
+
+	*blk_no = last_blk;
+bp_err:
+	xlog_put_bp(bp);
+	if (error)
+		return error;
+	return -1;
+}
+
+/*
+ * These are simple subroutines used by xlog_clear_stale_blocks() below
+ * to initialize a buffer full of empty log record headers and write
+ * them into the log.
+ */
+STATIC void
+xlog_add_record(
+	xlog_t			*log,
+	xfs_caddr_t		buf,
+	int			cycle,
+	int			block,
+	int			tail_cycle,
+	int			tail_block)
+{
+	xlog_rec_header_t	*recp = (xlog_rec_header_t *)buf;
+
+	memset(buf, 0, BBSIZE);
+	recp->h_magicno = cpu_to_be32(XLOG_HEADER_MAGIC_NUM);
+	recp->h_cycle = cpu_to_be32(cycle);
+	recp->h_version = cpu_to_be32(
+			xfs_sb_version_haslogv2(&log->l_mp->m_sb) ? 2 : 1);
+	recp->h_lsn = cpu_to_be64(xlog_assign_lsn(cycle, block));
+	recp->h_tail_lsn = cpu_to_be64(xlog_assign_lsn(tail_cycle, tail_block));
+	recp->h_fmt = cpu_to_be32(XLOG_FMT);
+	memcpy(&recp->h_fs_uuid, &log->l_mp->m_sb.sb_uuid, sizeof(uuid_t));
+}
+
+STATIC int
+xlog_write_log_records(
+	xlog_t		*log,
+	int		cycle,
+	int		start_block,
+	int		blocks,
+	int		tail_cycle,
+	int		tail_block)
+{
+	xfs_caddr_t	offset;
+	xfs_buf_t	*bp;
+	int		balign, ealign;
+	int		sectbb = log->l_sectBBsize;
+	int		end_block = start_block + blocks;
+	int		bufblks;
+	int		error = 0;
+	int		i, j = 0;
+
+	/*
+	 * Greedily allocate a buffer big enough to handle the full
+	 * range of basic blocks to be written.  If that fails, try
+	 * a smaller size.  We need to be able to write at least a
+	 * log sector, or we're out of luck.
+	 */
+	bufblks = 1 << ffs(blocks);
+	while (!(bp = xlog_get_bp(log, bufblks))) {
+		bufblks >>= 1;
+		if (bufblks < sectbb)
+			return ENOMEM;
+	}
+
+	/* We may need to do a read at the start to fill in part of
+	 * the buffer in the starting sector not covered by the first
+	 * write below.
+	 */
+	balign = round_down(start_block, sectbb);
+	if (balign != start_block) {
+		error = xlog_bread_noalign(log, start_block, 1, bp);
+		if (error)
+			goto out_put_bp;
+
+		j = start_block - balign;
+	}
+
+	for (i = start_block; i < end_block; i += bufblks) {
+		int		bcount, endcount;
+
+		bcount = min(bufblks, end_block - start_block);
+		endcount = bcount - j;
+
+		/* We may need to do a read at the end to fill in part of
+		 * the buffer in the final sector not covered by the write.
+		 * If this is the same sector as the above read, skip it.
+		 */
+		ealign = round_down(end_block, sectbb);
+		if (j == 0 && (start_block + endcount > ealign)) {
+			offset = bp->b_addr + BBTOB(ealign - start_block);
+			error = xlog_bread_offset(log, ealign, sectbb,
+							bp, offset);
+			if (error)
+				break;
+
+		}
+
+		offset = xlog_align(log, start_block, endcount, bp);
+		for (; j < endcount; j++) {
+			xlog_add_record(log, offset, cycle, i+j,
+					tail_cycle, tail_block);
+			offset += BBSIZE;
+		}
+		error = xlog_bwrite(log, start_block, endcount, bp);
+		if (error)
+			break;
+		start_block += endcount;
+		j = 0;
+	}
+
+ out_put_bp:
+	xlog_put_bp(bp);
+	return error;
+}
+
+/*
+ * This routine is called to blow away any incomplete log writes out
+ * in front of the log head.  We do this so that we won't become confused
+ * if we come up, write only a little bit more, and then crash again.
+ * If we leave the partial log records out there, this situation could
+ * cause us to think those partial writes are valid blocks since they
+ * have the current cycle number.  We get rid of them by overwriting them
+ * with empty log records with the old cycle number rather than the
+ * current one.
+ *
+ * The tail lsn is passed in rather than taken from
+ * the log so that we will not write over the unmount record after a
+ * clean unmount in a 512 block log.  Doing so would leave the log without
+ * any valid log records in it until a new one was written.  If we crashed
+ * during that time we would not be able to recover.
+ */
+STATIC int
+xlog_clear_stale_blocks(
+	xlog_t		*log,
+	xfs_lsn_t	tail_lsn)
+{
+	int		tail_cycle, head_cycle;
+	int		tail_block, head_block;
+	int		tail_distance, max_distance;
+	int		distance;
+	int		error;
+
+	tail_cycle = CYCLE_LSN(tail_lsn);
+	tail_block = BLOCK_LSN(tail_lsn);
+	head_cycle = log->l_curr_cycle;
+	head_block = log->l_curr_block;
+
+	/*
+	 * Figure out the distance between the new head of the log
+	 * and the tail.  We want to write over any blocks beyond the
+	 * head that we may have written just before the crash, but
+	 * we don't want to overwrite the tail of the log.
+	 */
+	if (head_cycle == tail_cycle) {
+		/*
+		 * The tail is behind the head in the physical log,
+		 * so the distance from the head to the tail is the
+		 * distance from the head to the end of the log plus
+		 * the distance from the beginning of the log to the
+		 * tail.
+		 */
+		if (unlikely(head_block < tail_block || head_block >= log->l_logBBsize)) {
+			XFS_ERROR_REPORT("xlog_clear_stale_blocks(1)",
+					 XFS_ERRLEVEL_LOW, log->l_mp);
+			return XFS_ERROR(EFSCORRUPTED);
+		}
+		tail_distance = tail_block + (log->l_logBBsize - head_block);
+	} else {
+		/*
+		 * The head is behind the tail in the physical log,
+		 * so the distance from the head to the tail is just
+		 * the tail block minus the head block.
+		 */
+		if (unlikely(head_block >= tail_block || head_cycle != (tail_cycle + 1))){
+			XFS_ERROR_REPORT("xlog_clear_stale_blocks(2)",
+					 XFS_ERRLEVEL_LOW, log->l_mp);
+			return XFS_ERROR(EFSCORRUPTED);
+		}
+		tail_distance = tail_block - head_block;
+	}
+
+	/*
+	 * If the head is right up against the tail, we can't clear
+	 * anything.
+	 */
+	if (tail_distance <= 0) {
+		ASSERT(tail_distance == 0);
+		return 0;
+	}
+
+	max_distance = XLOG_TOTAL_REC_SHIFT(log);
+	/*
+	 * Take the smaller of the maximum amount of outstanding I/O
+	 * we could have and the distance to the tail to clear out.
+	 * We take the smaller so that we don't overwrite the tail and
+	 * we don't waste all day writing from the head to the tail
+	 * for no reason.
+	 */
+	max_distance = MIN(max_distance, tail_distance);
+
+	if ((head_block + max_distance) <= log->l_logBBsize) {
+		/*
+		 * We can stomp all the blocks we need to without
+		 * wrapping around the end of the log.  Just do it
+		 * in a single write.  Use the cycle number of the
+		 * current cycle minus one so that the log will look like:
+		 *     n ... | n - 1 ...
+		 */
+		error = xlog_write_log_records(log, (head_cycle - 1),
+				head_block, max_distance, tail_cycle,
+				tail_block);
+		if (error)
+			return error;
+	} else {
+		/*
+		 * We need to wrap around the end of the physical log in
+		 * order to clear all the blocks.  Do it in two separate
+		 * I/Os.  The first write should be from the head to the
+		 * end of the physical log, and it should use the current
+		 * cycle number minus one just like above.
+		 */
+		distance = log->l_logBBsize - head_block;
+		error = xlog_write_log_records(log, (head_cycle - 1),
+				head_block, distance, tail_cycle,
+				tail_block);
+
+		if (error)
+			return error;
+
+		/*
+		 * Now write the blocks at the start of the physical log.
+		 * This writes the remainder of the blocks we want to clear.
+		 * It uses the current cycle number since we're now on the
+		 * same cycle as the head so that we get:
+		 *    n ... n ... | n - 1 ...
+		 *    ^^^^^ blocks we're writing
+		 */
+		distance = max_distance - (log->l_logBBsize - head_block);
+		error = xlog_write_log_records(log, head_cycle, 0, distance,
+				tail_cycle, tail_block);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/******************************************************************************
+ *
+ *		Log recover routines
+ *
+ ******************************************************************************
+ */
+
+STATIC xlog_recover_t *
+xlog_recover_find_tid(
+	struct hlist_head	*head,
+	xlog_tid_t		tid)
+{
+	xlog_recover_t		*trans;
+	struct hlist_node	*n;
+
+	hlist_for_each_entry(trans, n, head, r_list) {
+		if (trans->r_log_tid == tid)
+			return trans;
+	}
+	return NULL;
+}
+
+STATIC void
+xlog_recover_new_tid(
+	struct hlist_head	*head,
+	xlog_tid_t		tid,
+	xfs_lsn_t		lsn)
+{
+	xlog_recover_t		*trans;
+
+	trans = kmem_zalloc(sizeof(xlog_recover_t), KM_SLEEP);
+	trans->r_log_tid   = tid;
+	trans->r_lsn	   = lsn;
+	INIT_LIST_HEAD(&trans->r_itemq);
+
+	INIT_HLIST_NODE(&trans->r_list);
+	hlist_add_head(&trans->r_list, head);
+}
+
+STATIC void
+xlog_recover_add_item(
+	struct list_head	*head)
+{
+	xlog_recover_item_t	*item;
+
+	item = kmem_zalloc(sizeof(xlog_recover_item_t), KM_SLEEP);
+	INIT_LIST_HEAD(&item->ri_list);
+	list_add_tail(&item->ri_list, head);
+}
+
+STATIC int
+xlog_recover_add_to_cont_trans(
+	struct log		*log,
+	xlog_recover_t		*trans,
+	xfs_caddr_t		dp,
+	int			len)
+{
+	xlog_recover_item_t	*item;
+	xfs_caddr_t		ptr, old_ptr;
+	int			old_len;
+
+	if (list_empty(&trans->r_itemq)) {
+		/* finish copying rest of trans header */
+		xlog_recover_add_item(&trans->r_itemq);
+		ptr = (xfs_caddr_t) &trans->r_theader +
+				sizeof(xfs_trans_header_t) - len;
+		memcpy(ptr, dp, len); /* d, s, l */
+		return 0;
+	}
+	/* take the tail entry */
+	item = list_entry(trans->r_itemq.prev, xlog_recover_item_t, ri_list);
+
+	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
+	old_len = item->ri_buf[item->ri_cnt-1].i_len;
+
+	ptr = kmem_realloc(old_ptr, len+old_len, old_len, KM_SLEEP);
+	memcpy(&ptr[old_len], dp, len); /* d, s, l */
+	item->ri_buf[item->ri_cnt-1].i_len += len;
+	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
+	trace_xfs_log_recover_item_add_cont(log, trans, item, 0);
+	return 0;
+}
+
+/*
+ * The next region to add is the start of a new region.  It could be
+ * a whole region or it could be the first part of a new region.  Because
+ * of this, the assumption here is that the type and size fields of all
+ * format structures fit into the first 32 bits of the structure.
+ *
+ * This works because all regions must be 32 bit aligned.  Therefore, we
+ * either have both fields or we have neither field.  In the case we have
+ * neither field, the data part of the region is zero length.  We only have
+ * a log_op_header and can throw away the header since a new one will appear
+ * later.  If we have at least 4 bytes, then we can determine how many regions
+ * will appear in the current log item.
+ */
+STATIC int
+xlog_recover_add_to_trans(
+	struct log		*log,
+	xlog_recover_t		*trans,
+	xfs_caddr_t		dp,
+	int			len)
+{
+	xfs_inode_log_format_t	*in_f;			/* any will do */
+	xlog_recover_item_t	*item;
+	xfs_caddr_t		ptr;
+
+	if (!len)
+		return 0;
+	if (list_empty(&trans->r_itemq)) {
+		/* we need to catch log corruptions here */
+		if (*(uint *)dp != XFS_TRANS_HEADER_MAGIC) {
+			xfs_warn(log->l_mp, "%s: bad header magic number",
+				__func__);
+			ASSERT(0);
+			return XFS_ERROR(EIO);
+		}
+		if (len == sizeof(xfs_trans_header_t))
+			xlog_recover_add_item(&trans->r_itemq);
+		memcpy(&trans->r_theader, dp, len); /* d, s, l */
+		return 0;
+	}
+
+	ptr = kmem_alloc(len, KM_SLEEP);
+	memcpy(ptr, dp, len);
+	in_f = (xfs_inode_log_format_t *)ptr;
+
+	/* take the tail entry */
+	item = list_entry(trans->r_itemq.prev, xlog_recover_item_t, ri_list);
+	if (item->ri_total != 0 &&
+	     item->ri_total == item->ri_cnt) {
+		/* tail item is in use, get a new one */
+		xlog_recover_add_item(&trans->r_itemq);
+		item = list_entry(trans->r_itemq.prev,
+					xlog_recover_item_t, ri_list);
+	}
+
+	if (item->ri_total == 0) {		/* first region to be added */
+		if (in_f->ilf_size == 0 ||
+		    in_f->ilf_size > XLOG_MAX_REGIONS_IN_ITEM) {
+			xfs_warn(log->l_mp,
+		"bad number of regions (%d) in inode log format",
+				  in_f->ilf_size);
+			ASSERT(0);
+			return XFS_ERROR(EIO);
+		}
+
+		item->ri_total = in_f->ilf_size;
+		item->ri_buf =
+			kmem_zalloc(item->ri_total * sizeof(xfs_log_iovec_t),
+				    KM_SLEEP);
+	}
+	ASSERT(item->ri_total > item->ri_cnt);
+	/* Description region is ri_buf[0] */
+	item->ri_buf[item->ri_cnt].i_addr = ptr;
+	item->ri_buf[item->ri_cnt].i_len  = len;
+	item->ri_cnt++;
+	trace_xfs_log_recover_item_add(log, trans, item, 0);
+	return 0;
+}
+
+/*
+ * Sort the log items in the transaction. Cancelled buffers need
+ * to be put first so they are processed before any items that might
+ * modify the buffers. If they are cancelled, then the modifications
+ * don't need to be replayed.
+ */
+STATIC int
+xlog_recover_reorder_trans(
+	struct log		*log,
+	xlog_recover_t		*trans,
+	int			pass)
+{
+	xlog_recover_item_t	*item, *n;
+	LIST_HEAD(sort_list);
+
+	list_splice_init(&trans->r_itemq, &sort_list);
+	list_for_each_entry_safe(item, n, &sort_list, ri_list) {
+		xfs_buf_log_format_t	*buf_f = item->ri_buf[0].i_addr;
+
+		switch (ITEM_TYPE(item)) {
+		case XFS_LI_BUF:
+			if (!(buf_f->blf_flags & XFS_BLF_CANCEL)) {
+				trace_xfs_log_recover_item_reorder_head(log,
+							trans, item, pass);
+				list_move(&item->ri_list, &trans->r_itemq);
+				break;
+			}
+		case XFS_LI_INODE:
+		case XFS_LI_DQUOT:
+		case XFS_LI_QUOTAOFF:
+		case XFS_LI_EFD:
+		case XFS_LI_EFI:
+			trace_xfs_log_recover_item_reorder_tail(log,
+							trans, item, pass);
+			list_move_tail(&item->ri_list, &trans->r_itemq);
+			break;
+		default:
+			xfs_warn(log->l_mp,
+				"%s: unrecognized type of log operation",
+				__func__);
+			ASSERT(0);
+			return XFS_ERROR(EIO);
+		}
+	}
+	ASSERT(list_empty(&sort_list));
+	return 0;
+}
+
+/*
+ * Build up the table of buf cancel records so that we don't replay
+ * cancelled data in the second pass.  For buffer records that are
+ * not cancel records, there is nothing to do here so we just return.
+ *
+ * If we get a cancel record which is already in the table, this indicates
+ * that the buffer was cancelled multiple times.  In order to ensure
+ * that during pass 2 we keep the record in the table until we reach its
+ * last occurrence in the log, we keep a reference count in the cancel
+ * record in the table to tell us how many times we expect to see this
+ * record during the second pass.
+ */
+STATIC int
+xlog_recover_buffer_pass1(
+	struct log		*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_buf_log_format_t	*buf_f = item->ri_buf[0].i_addr;
+	struct list_head	*bucket;
+	struct xfs_buf_cancel	*bcp;
+
+	/*
+	 * If this isn't a cancel buffer item, then just return.
+	 */
+	if (!(buf_f->blf_flags & XFS_BLF_CANCEL)) {
+		trace_xfs_log_recover_buf_not_cancel(log, buf_f);
+		return 0;
+	}
+
+	/*
+	 * Insert an xfs_buf_cancel record into the hash table of them.
+	 * If there is already an identical record, bump its reference count.
+	 */
+	bucket = XLOG_BUF_CANCEL_BUCKET(log, buf_f->blf_blkno);
+	list_for_each_entry(bcp, bucket, bc_list) {
+		if (bcp->bc_blkno == buf_f->blf_blkno &&
+		    bcp->bc_len == buf_f->blf_len) {
+			bcp->bc_refcount++;
+			trace_xfs_log_recover_buf_cancel_ref_inc(log, buf_f);
+			return 0;
+		}
+	}
+
+	bcp = kmem_alloc(sizeof(struct xfs_buf_cancel), KM_SLEEP);
+	bcp->bc_blkno = buf_f->blf_blkno;
+	bcp->bc_len = buf_f->blf_len;
+	bcp->bc_refcount = 1;
+	list_add_tail(&bcp->bc_list, bucket);
+
+	trace_xfs_log_recover_buf_cancel_add(log, buf_f);
+	return 0;
+}
+
+/*
+ * Check to see whether the buffer being recovered has a corresponding
+ * entry in the buffer cancel record table.  If it does then return 1
+ * so that it will be cancelled, otherwise return 0.  If the buffer is
+ * actually a buffer cancel item (XFS_BLF_CANCEL is set), then decrement
+ * the refcount on the entry in the table and remove it from the table
+ * if this is the last reference.
+ *
+ * We remove the cancel record from the table when we encounter its
+ * last occurrence in the log so that if the same buffer is re-used
+ * again after its last cancellation we actually replay the changes
+ * made at that point.
+ */
+STATIC int
+xlog_check_buffer_cancelled(
+	struct log		*log,
+	xfs_daddr_t		blkno,
+	uint			len,
+	ushort			flags)
+{
+	struct list_head	*bucket;
+	struct xfs_buf_cancel	*bcp;
+
+	if (log->l_buf_cancel_table == NULL) {
+		/*
+		 * There is nothing in the table built in pass one,
+		 * so this buffer must not be cancelled.
+		 */
+		ASSERT(!(flags & XFS_BLF_CANCEL));
+		return 0;
+	}
+
+	/*
+	 * Search for an entry in the  cancel table that matches our buffer.
+	 */
+	bucket = XLOG_BUF_CANCEL_BUCKET(log, blkno);
+	list_for_each_entry(bcp, bucket, bc_list) {
+		if (bcp->bc_blkno == blkno && bcp->bc_len == len)
+			goto found;
+	}
+
+	/*
+	 * We didn't find a corresponding entry in the table, so return 0 so
+	 * that the buffer is NOT cancelled.
+	 */
+	ASSERT(!(flags & XFS_BLF_CANCEL));
+	return 0;
+
+found:
+	/*
+	 * We've go a match, so return 1 so that the recovery of this buffer
+	 * is cancelled.  If this buffer is actually a buffer cancel log
+	 * item, then decrement the refcount on the one in the table and
+	 * remove it if this is the last reference.
+	 */
+	if (flags & XFS_BLF_CANCEL) {
+		if (--bcp->bc_refcount == 0) {
+			list_del(&bcp->bc_list);
+			kmem_free(bcp);
+		}
+	}
+	return 1;
+}
+
+/*
+ * Perform recovery for a buffer full of inodes.  In these buffers, the only
+ * data which should be recovered is that which corresponds to the
+ * di_next_unlinked pointers in the on disk inode structures.  The rest of the
+ * data for the inodes is always logged through the inodes themselves rather
+ * than the inode buffer and is recovered in xlog_recover_inode_pass2().
+ *
+ * The only time when buffers full of inodes are fully recovered is when the
+ * buffer is full of newly allocated inodes.  In this case the buffer will
+ * not be marked as an inode buffer and so will be sent to
+ * xlog_recover_do_reg_buffer() below during recovery.
+ */
+STATIC int
+xlog_recover_do_inode_buffer(
+	struct xfs_mount	*mp,
+	xlog_recover_item_t	*item,
+	struct xfs_buf		*bp,
+	xfs_buf_log_format_t	*buf_f)
+{
+	int			i;
+	int			item_index = 0;
+	int			bit = 0;
+	int			nbits = 0;
+	int			reg_buf_offset = 0;
+	int			reg_buf_bytes = 0;
+	int			next_unlinked_offset;
+	int			inodes_per_buf;
+	xfs_agino_t		*logged_nextp;
+	xfs_agino_t		*buffer_nextp;
+
+	trace_xfs_log_recover_buf_inode_buf(mp->m_log, buf_f);
+
+	inodes_per_buf = XFS_BUF_COUNT(bp) >> mp->m_sb.sb_inodelog;
+	for (i = 0; i < inodes_per_buf; i++) {
+		next_unlinked_offset = (i * mp->m_sb.sb_inodesize) +
+			offsetof(xfs_dinode_t, di_next_unlinked);
+
+		while (next_unlinked_offset >=
+		       (reg_buf_offset + reg_buf_bytes)) {
+			/*
+			 * The next di_next_unlinked field is beyond
+			 * the current logged region.  Find the next
+			 * logged region that contains or is beyond
+			 * the current di_next_unlinked field.
+			 */
+			bit += nbits;
+			bit = xfs_next_bit(buf_f->blf_data_map,
+					   buf_f->blf_map_size, bit);
+
+			/*
+			 * If there are no more logged regions in the
+			 * buffer, then we're done.
+			 */
+			if (bit == -1)
+				return 0;
+
+			nbits = xfs_contig_bits(buf_f->blf_data_map,
+						buf_f->blf_map_size, bit);
+			ASSERT(nbits > 0);
+			reg_buf_offset = bit << XFS_BLF_SHIFT;
+			reg_buf_bytes = nbits << XFS_BLF_SHIFT;
+			item_index++;
+		}
+
+		/*
+		 * If the current logged region starts after the current
+		 * di_next_unlinked field, then move on to the next
+		 * di_next_unlinked field.
+		 */
+		if (next_unlinked_offset < reg_buf_offset)
+			continue;
+
+		ASSERT(item->ri_buf[item_index].i_addr != NULL);
+		ASSERT((item->ri_buf[item_index].i_len % XFS_BLF_CHUNK) == 0);
+		ASSERT((reg_buf_offset + reg_buf_bytes) <= XFS_BUF_COUNT(bp));
+
+		/*
+		 * The current logged region contains a copy of the
+		 * current di_next_unlinked field.  Extract its value
+		 * and copy it to the buffer copy.
+		 */
+		logged_nextp = item->ri_buf[item_index].i_addr +
+				next_unlinked_offset - reg_buf_offset;
+		if (unlikely(*logged_nextp == 0)) {
+			xfs_alert(mp,
+		"Bad inode buffer log record (ptr = 0x%p, bp = 0x%p). "
+		"Trying to replay bad (0) inode di_next_unlinked field.",
+				item, bp);
+			XFS_ERROR_REPORT("xlog_recover_do_inode_buf",
+					 XFS_ERRLEVEL_LOW, mp);
+			return XFS_ERROR(EFSCORRUPTED);
+		}
+
+		buffer_nextp = (xfs_agino_t *)xfs_buf_offset(bp,
+					      next_unlinked_offset);
+		*buffer_nextp = *logged_nextp;
+	}
+
+	return 0;
+}
+
+/*
+ * Perform a 'normal' buffer recovery.  Each logged region of the
+ * buffer should be copied over the corresponding region in the
+ * given buffer.  The bitmap in the buf log format structure indicates
+ * where to place the logged data.
+ */
+STATIC void
+xlog_recover_do_reg_buffer(
+	struct xfs_mount	*mp,
+	xlog_recover_item_t	*item,
+	struct xfs_buf		*bp,
+	xfs_buf_log_format_t	*buf_f)
+{
+	int			i;
+	int			bit;
+	int			nbits;
+	int                     error;
+
+	trace_xfs_log_recover_buf_reg_buf(mp->m_log, buf_f);
+
+	bit = 0;
+	i = 1;  /* 0 is the buf format structure */
+	while (1) {
+		bit = xfs_next_bit(buf_f->blf_data_map,
+				   buf_f->blf_map_size, bit);
+		if (bit == -1)
+			break;
+		nbits = xfs_contig_bits(buf_f->blf_data_map,
+					buf_f->blf_map_size, bit);
+		ASSERT(nbits > 0);
+		ASSERT(item->ri_buf[i].i_addr != NULL);
+		ASSERT(item->ri_buf[i].i_len % XFS_BLF_CHUNK == 0);
+		ASSERT(XFS_BUF_COUNT(bp) >=
+		       ((uint)bit << XFS_BLF_SHIFT)+(nbits<<XFS_BLF_SHIFT));
+
+		/*
+		 * Do a sanity check if this is a dquot buffer. Just checking
+		 * the first dquot in the buffer should do. XXXThis is
+		 * probably a good thing to do for other buf types also.
+		 */
+		error = 0;
+		if (buf_f->blf_flags &
+		   (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
+			if (item->ri_buf[i].i_addr == NULL) {
+				xfs_alert(mp,
+					"XFS: NULL dquot in %s.", __func__);
+				goto next;
+			}
+			if (item->ri_buf[i].i_len < sizeof(xfs_disk_dquot_t)) {
+				xfs_alert(mp,
+					"XFS: dquot too small (%d) in %s.",
+					item->ri_buf[i].i_len, __func__);
+				goto next;
+			}
+			error = xfs_qm_dqcheck(mp, item->ri_buf[i].i_addr,
+					       -1, 0, XFS_QMOPT_DOWARN,
+					       "dquot_buf_recover");
+			if (error)
+				goto next;
+		}
+
+		memcpy(xfs_buf_offset(bp,
+			(uint)bit << XFS_BLF_SHIFT),	/* dest */
+			item->ri_buf[i].i_addr,		/* source */
+			nbits<<XFS_BLF_SHIFT);		/* length */
+ next:
+		i++;
+		bit += nbits;
+	}
+
+	/* Shouldn't be any more regions */
+	ASSERT(i == item->ri_total);
+}
+
+/*
+ * Do some primitive error checking on ondisk dquot data structures.
+ */
+int
+xfs_qm_dqcheck(
+	struct xfs_mount *mp,
+	xfs_disk_dquot_t *ddq,
+	xfs_dqid_t	 id,
+	uint		 type,	  /* used only when IO_dorepair is true */
+	uint		 flags,
+	char		 *str)
+{
+	xfs_dqblk_t	 *d = (xfs_dqblk_t *)ddq;
+	int		errs = 0;
+
+	/*
+	 * We can encounter an uninitialized dquot buffer for 2 reasons:
+	 * 1. If we crash while deleting the quotainode(s), and those blks got
+	 *    used for user data. This is because we take the path of regular
+	 *    file deletion; however, the size field of quotainodes is never
+	 *    updated, so all the tricks that we play in itruncate_finish
+	 *    don't quite matter.
+	 *
+	 * 2. We don't play the quota buffers when there's a quotaoff logitem.
+	 *    But the allocation will be replayed so we'll end up with an
+	 *    uninitialized quota block.
+	 *
+	 * This is all fine; things are still consistent, and we haven't lost
+	 * any quota information. Just don't complain about bad dquot blks.
+	 */
+	if (ddq->d_magic != cpu_to_be16(XFS_DQUOT_MAGIC)) {
+		if (flags & XFS_QMOPT_DOWARN)
+			xfs_alert(mp,
+			"%s : XFS dquot ID 0x%x, magic 0x%x != 0x%x",
+			str, id, be16_to_cpu(ddq->d_magic), XFS_DQUOT_MAGIC);
+		errs++;
+	}
+	if (ddq->d_version != XFS_DQUOT_VERSION) {
+		if (flags & XFS_QMOPT_DOWARN)
+			xfs_alert(mp,
+			"%s : XFS dquot ID 0x%x, version 0x%x != 0x%x",
+			str, id, ddq->d_version, XFS_DQUOT_VERSION);
+		errs++;
+	}
+
+	if (ddq->d_flags != XFS_DQ_USER &&
+	    ddq->d_flags != XFS_DQ_PROJ &&
+	    ddq->d_flags != XFS_DQ_GROUP) {
+		if (flags & XFS_QMOPT_DOWARN)
+			xfs_alert(mp,
+			"%s : XFS dquot ID 0x%x, unknown flags 0x%x",
+			str, id, ddq->d_flags);
+		errs++;
+	}
+
+	if (id != -1 && id != be32_to_cpu(ddq->d_id)) {
+		if (flags & XFS_QMOPT_DOWARN)
+			xfs_alert(mp,
+			"%s : ondisk-dquot 0x%p, ID mismatch: "
+			"0x%x expected, found id 0x%x",
+			str, ddq, id, be32_to_cpu(ddq->d_id));
+		errs++;
+	}
+
+	if (!errs && ddq->d_id) {
+		if (ddq->d_blk_softlimit &&
+		    be64_to_cpu(ddq->d_bcount) >
+				be64_to_cpu(ddq->d_blk_softlimit)) {
+			if (!ddq->d_btimer) {
+				if (flags & XFS_QMOPT_DOWARN)
+					xfs_alert(mp,
+			"%s : Dquot ID 0x%x (0x%p) BLK TIMER NOT STARTED",
+					str, (int)be32_to_cpu(ddq->d_id), ddq);
+				errs++;
+			}
+		}
+		if (ddq->d_ino_softlimit &&
+		    be64_to_cpu(ddq->d_icount) >
+				be64_to_cpu(ddq->d_ino_softlimit)) {
+			if (!ddq->d_itimer) {
+				if (flags & XFS_QMOPT_DOWARN)
+					xfs_alert(mp,
+			"%s : Dquot ID 0x%x (0x%p) INODE TIMER NOT STARTED",
+					str, (int)be32_to_cpu(ddq->d_id), ddq);
+				errs++;
+			}
+		}
+		if (ddq->d_rtb_softlimit &&
+		    be64_to_cpu(ddq->d_rtbcount) >
+				be64_to_cpu(ddq->d_rtb_softlimit)) {
+			if (!ddq->d_rtbtimer) {
+				if (flags & XFS_QMOPT_DOWARN)
+					xfs_alert(mp,
+			"%s : Dquot ID 0x%x (0x%p) RTBLK TIMER NOT STARTED",
+					str, (int)be32_to_cpu(ddq->d_id), ddq);
+				errs++;
+			}
+		}
+	}
+
+	if (!errs || !(flags & XFS_QMOPT_DQREPAIR))
+		return errs;
+
+	if (flags & XFS_QMOPT_DOWARN)
+		xfs_notice(mp, "Re-initializing dquot ID 0x%x", id);
+
+	/*
+	 * Typically, a repair is only requested by quotacheck.
+	 */
+	ASSERT(id != -1);
+	ASSERT(flags & XFS_QMOPT_DQREPAIR);
+	memset(d, 0, sizeof(xfs_dqblk_t));
+
+	d->dd_diskdq.d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
+	d->dd_diskdq.d_version = XFS_DQUOT_VERSION;
+	d->dd_diskdq.d_flags = type;
+	d->dd_diskdq.d_id = cpu_to_be32(id);
+
+	return errs;
+}
+
+/*
+ * Perform a dquot buffer recovery.
+ * Simple algorithm: if we have found a QUOTAOFF logitem of the same type
+ * (ie. USR or GRP), then just toss this buffer away; don't recover it.
+ * Else, treat it as a regular buffer and do recovery.
+ */
+STATIC void
+xlog_recover_do_dquot_buffer(
+	xfs_mount_t		*mp,
+	xlog_t			*log,
+	xlog_recover_item_t	*item,
+	xfs_buf_t		*bp,
+	xfs_buf_log_format_t	*buf_f)
+{
+	uint			type;
+
+	trace_xfs_log_recover_buf_dquot_buf(log, buf_f);
+
+	/*
+	 * Filesystems are required to send in quota flags at mount time.
+	 */
+	if (mp->m_qflags == 0) {
+		return;
+	}
+
+	type = 0;
+	if (buf_f->blf_flags & XFS_BLF_UDQUOT_BUF)
+		type |= XFS_DQ_USER;
+	if (buf_f->blf_flags & XFS_BLF_PDQUOT_BUF)
+		type |= XFS_DQ_PROJ;
+	if (buf_f->blf_flags & XFS_BLF_GDQUOT_BUF)
+		type |= XFS_DQ_GROUP;
+	/*
+	 * This type of quotas was turned off, so ignore this buffer
+	 */
+	if (log->l_quotaoffs_flag & type)
+		return;
+
+	xlog_recover_do_reg_buffer(mp, item, bp, buf_f);
+}
+
+/*
+ * This routine replays a modification made to a buffer at runtime.
+ * There are actually two types of buffer, regular and inode, which
+ * are handled differently.  Inode buffers are handled differently
+ * in that we only recover a specific set of data from them, namely
+ * the inode di_next_unlinked fields.  This is because all other inode
+ * data is actually logged via inode records and any data we replay
+ * here which overlaps that may be stale.
+ *
+ * When meta-data buffers are freed at run time we log a buffer item
+ * with the XFS_BLF_CANCEL bit set to indicate that previous copies
+ * of the buffer in the log should not be replayed at recovery time.
+ * This is so that if the blocks covered by the buffer are reused for
+ * file data before we crash we don't end up replaying old, freed
+ * meta-data into a user's file.
+ *
+ * To handle the cancellation of buffer log items, we make two passes
+ * over the log during recovery.  During the first we build a table of
+ * those buffers which have been cancelled, and during the second we
+ * only replay those buffers which do not have corresponding cancel
+ * records in the table.  See xlog_recover_do_buffer_pass[1,2] above
+ * for more details on the implementation of the table of cancel records.
+ */
+STATIC int
+xlog_recover_buffer_pass2(
+	xlog_t			*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_buf_log_format_t	*buf_f = item->ri_buf[0].i_addr;
+	xfs_mount_t		*mp = log->l_mp;
+	xfs_buf_t		*bp;
+	int			error;
+	uint			buf_flags;
+
+	/*
+	 * In this pass we only want to recover all the buffers which have
+	 * not been cancelled and are not cancellation buffers themselves.
+	 */
+	if (xlog_check_buffer_cancelled(log, buf_f->blf_blkno,
+			buf_f->blf_len, buf_f->blf_flags)) {
+		trace_xfs_log_recover_buf_cancel(log, buf_f);
+		return 0;
+	}
+
+	trace_xfs_log_recover_buf_recover(log, buf_f);
+
+	buf_flags = XBF_LOCK;
+	if (!(buf_f->blf_flags & XFS_BLF_INODE_BUF))
+		buf_flags |= XBF_MAPPED;
+
+	bp = xfs_buf_read(mp->m_ddev_targp, buf_f->blf_blkno, buf_f->blf_len,
+			  buf_flags);
+	if (!bp)
+		return XFS_ERROR(ENOMEM);
+	error = bp->b_error;
+	if (error) {
+		xfs_buf_ioerror_alert(bp, "xlog_recover_do..(read#1)");
+		xfs_buf_relse(bp);
+		return error;
+	}
+
+	if (buf_f->blf_flags & XFS_BLF_INODE_BUF) {
+		error = xlog_recover_do_inode_buffer(mp, item, bp, buf_f);
+	} else if (buf_f->blf_flags &
+		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
+		xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+	} else {
+		xlog_recover_do_reg_buffer(mp, item, bp, buf_f);
+	}
+	if (error)
+		return XFS_ERROR(error);
+
+	/*
+	 * Perform delayed write on the buffer.  Asynchronous writes will be
+	 * slower when taking into account all the buffers to be flushed.
+	 *
+	 * Also make sure that only inode buffers with good sizes stay in
+	 * the buffer cache.  The kernel moves inodes in buffers of 1 block
+	 * or XFS_INODE_CLUSTER_SIZE bytes, whichever is bigger.  The inode
+	 * buffers in the log can be a different size if the log was generated
+	 * by an older kernel using unclustered inode buffers or a newer kernel
+	 * running with a different inode cluster size.  Regardless, if the
+	 * the inode buffer size isn't MAX(blocksize, XFS_INODE_CLUSTER_SIZE)
+	 * for *our* value of XFS_INODE_CLUSTER_SIZE, then we need to keep
+	 * the buffer out of the buffer cache so that the buffer won't
+	 * overlap with future reads of those inodes.
+	 */
+	if (XFS_DINODE_MAGIC ==
+	    be16_to_cpu(*((__be16 *)xfs_buf_offset(bp, 0))) &&
+	    (XFS_BUF_COUNT(bp) != MAX(log->l_mp->m_sb.sb_blocksize,
+			(__uint32_t)XFS_INODE_CLUSTER_SIZE(log->l_mp)))) {
+		xfs_buf_stale(bp);
+		error = xfs_bwrite(bp);
+	} else {
+		ASSERT(bp->b_target->bt_mount == mp);
+		bp->b_iodone = xlog_recover_iodone;
+		xfs_buf_delwri_queue(bp);
+	}
+
+	xfs_buf_relse(bp);
+	return error;
+}
+
+STATIC int
+xlog_recover_inode_pass2(
+	xlog_t			*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_inode_log_format_t	*in_f;
+	xfs_mount_t		*mp = log->l_mp;
+	xfs_buf_t		*bp;
+	xfs_dinode_t		*dip;
+	int			len;
+	xfs_caddr_t		src;
+	xfs_caddr_t		dest;
+	int			error;
+	int			attr_index;
+	uint			fields;
+	xfs_icdinode_t		*dicp;
+	int			need_free = 0;
+
+	if (item->ri_buf[0].i_len == sizeof(xfs_inode_log_format_t)) {
+		in_f = item->ri_buf[0].i_addr;
+	} else {
+		in_f = kmem_alloc(sizeof(xfs_inode_log_format_t), KM_SLEEP);
+		need_free = 1;
+		error = xfs_inode_item_format_convert(&item->ri_buf[0], in_f);
+		if (error)
+			goto error;
+	}
+
+	/*
+	 * Inode buffers can be freed, look out for it,
+	 * and do not replay the inode.
+	 */
+	if (xlog_check_buffer_cancelled(log, in_f->ilf_blkno,
+					in_f->ilf_len, 0)) {
+		error = 0;
+		trace_xfs_log_recover_inode_cancel(log, in_f);
+		goto error;
+	}
+	trace_xfs_log_recover_inode_recover(log, in_f);
+
+	bp = xfs_buf_read(mp->m_ddev_targp, in_f->ilf_blkno, in_f->ilf_len,
+			  XBF_LOCK);
+	if (!bp) {
+		error = ENOMEM;
+		goto error;
+	}
+	error = bp->b_error;
+	if (error) {
+		xfs_buf_ioerror_alert(bp, "xlog_recover_do..(read#2)");
+		xfs_buf_relse(bp);
+		goto error;
+	}
+	ASSERT(in_f->ilf_fields & XFS_ILOG_CORE);
+	dip = (xfs_dinode_t *)xfs_buf_offset(bp, in_f->ilf_boffset);
+
+	/*
+	 * Make sure the place we're flushing out to really looks
+	 * like an inode!
+	 */
+	if (unlikely(dip->di_magic != cpu_to_be16(XFS_DINODE_MAGIC))) {
+		xfs_buf_relse(bp);
+		xfs_alert(mp,
+	"%s: Bad inode magic number, dip = 0x%p, dino bp = 0x%p, ino = %Ld",
+			__func__, dip, bp, in_f->ilf_ino);
+		XFS_ERROR_REPORT("xlog_recover_inode_pass2(1)",
+				 XFS_ERRLEVEL_LOW, mp);
+		error = EFSCORRUPTED;
+		goto error;
+	}
+	dicp = item->ri_buf[1].i_addr;
+	if (unlikely(dicp->di_magic != XFS_DINODE_MAGIC)) {
+		xfs_buf_relse(bp);
+		xfs_alert(mp,
+			"%s: Bad inode log record, rec ptr 0x%p, ino %Ld",
+			__func__, item, in_f->ilf_ino);
+		XFS_ERROR_REPORT("xlog_recover_inode_pass2(2)",
+				 XFS_ERRLEVEL_LOW, mp);
+		error = EFSCORRUPTED;
+		goto error;
+	}
+
+	/* Skip replay when the on disk inode is newer than the log one */
+	if (dicp->di_flushiter < be16_to_cpu(dip->di_flushiter)) {
+		/*
+		 * Deal with the wrap case, DI_MAX_FLUSH is less
+		 * than smaller numbers
+		 */
+		if (be16_to_cpu(dip->di_flushiter) == DI_MAX_FLUSH &&
+		    dicp->di_flushiter < (DI_MAX_FLUSH >> 1)) {
+			/* do nothing */
+		} else {
+			xfs_buf_relse(bp);
+			trace_xfs_log_recover_inode_skip(log, in_f);
+			error = 0;
+			goto error;
+		}
+	}
+	/* Take the opportunity to reset the flush iteration count */
+	dicp->di_flushiter = 0;
+
+	if (unlikely(S_ISREG(dicp->di_mode))) {
+		if ((dicp->di_format != XFS_DINODE_FMT_EXTENTS) &&
+		    (dicp->di_format != XFS_DINODE_FMT_BTREE)) {
+			XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(3)",
+					 XFS_ERRLEVEL_LOW, mp, dicp);
+			xfs_buf_relse(bp);
+			xfs_alert(mp,
+		"%s: Bad regular inode log record, rec ptr 0x%p, "
+		"ino ptr = 0x%p, ino bp = 0x%p, ino %Ld",
+				__func__, item, dip, bp, in_f->ilf_ino);
+			error = EFSCORRUPTED;
+			goto error;
+		}
+	} else if (unlikely(S_ISDIR(dicp->di_mode))) {
+		if ((dicp->di_format != XFS_DINODE_FMT_EXTENTS) &&
+		    (dicp->di_format != XFS_DINODE_FMT_BTREE) &&
+		    (dicp->di_format != XFS_DINODE_FMT_LOCAL)) {
+			XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(4)",
+					     XFS_ERRLEVEL_LOW, mp, dicp);
+			xfs_buf_relse(bp);
+			xfs_alert(mp,
+		"%s: Bad dir inode log record, rec ptr 0x%p, "
+		"ino ptr = 0x%p, ino bp = 0x%p, ino %Ld",
+				__func__, item, dip, bp, in_f->ilf_ino);
+			error = EFSCORRUPTED;
+			goto error;
+		}
+	}
+	if (unlikely(dicp->di_nextents + dicp->di_anextents > dicp->di_nblocks)){
+		XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(5)",
+				     XFS_ERRLEVEL_LOW, mp, dicp);
+		xfs_buf_relse(bp);
+		xfs_alert(mp,
+	"%s: Bad inode log record, rec ptr 0x%p, dino ptr 0x%p, "
+	"dino bp 0x%p, ino %Ld, total extents = %d, nblocks = %Ld",
+			__func__, item, dip, bp, in_f->ilf_ino,
+			dicp->di_nextents + dicp->di_anextents,
+			dicp->di_nblocks);
+		error = EFSCORRUPTED;
+		goto error;
+	}
+	if (unlikely(dicp->di_forkoff > mp->m_sb.sb_inodesize)) {
+		XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(6)",
+				     XFS_ERRLEVEL_LOW, mp, dicp);
+		xfs_buf_relse(bp);
+		xfs_alert(mp,
+	"%s: Bad inode log record, rec ptr 0x%p, dino ptr 0x%p, "
+	"dino bp 0x%p, ino %Ld, forkoff 0x%x", __func__,
+			item, dip, bp, in_f->ilf_ino, dicp->di_forkoff);
+		error = EFSCORRUPTED;
+		goto error;
+	}
+	if (unlikely(item->ri_buf[1].i_len > sizeof(struct xfs_icdinode))) {
+		XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(7)",
+				     XFS_ERRLEVEL_LOW, mp, dicp);
+		xfs_buf_relse(bp);
+		xfs_alert(mp,
+			"%s: Bad inode log record length %d, rec ptr 0x%p",
+			__func__, item->ri_buf[1].i_len, item);
+		error = EFSCORRUPTED;
+		goto error;
+	}
+
+	/* The core is in in-core format */
+	xfs_dinode_to_disk(dip, item->ri_buf[1].i_addr);
+
+	/* the rest is in on-disk format */
+	if (item->ri_buf[1].i_len > sizeof(struct xfs_icdinode)) {
+		memcpy((xfs_caddr_t) dip + sizeof(struct xfs_icdinode),
+			item->ri_buf[1].i_addr + sizeof(struct xfs_icdinode),
+			item->ri_buf[1].i_len  - sizeof(struct xfs_icdinode));
+	}
+
+	fields = in_f->ilf_fields;
+	switch (fields & (XFS_ILOG_DEV | XFS_ILOG_UUID)) {
+	case XFS_ILOG_DEV:
+		xfs_dinode_put_rdev(dip, in_f->ilf_u.ilfu_rdev);
+		break;
+	case XFS_ILOG_UUID:
+		memcpy(XFS_DFORK_DPTR(dip),
+		       &in_f->ilf_u.ilfu_uuid,
+		       sizeof(uuid_t));
+		break;
+	}
+
+	if (in_f->ilf_size == 2)
+		goto write_inode_buffer;
+	len = item->ri_buf[2].i_len;
+	src = item->ri_buf[2].i_addr;
+	ASSERT(in_f->ilf_size <= 4);
+	ASSERT((in_f->ilf_size == 3) || (fields & XFS_ILOG_AFORK));
+	ASSERT(!(fields & XFS_ILOG_DFORK) ||
+	       (len == in_f->ilf_dsize));
+
+	switch (fields & XFS_ILOG_DFORK) {
+	case XFS_ILOG_DDATA:
+	case XFS_ILOG_DEXT:
+		memcpy(XFS_DFORK_DPTR(dip), src, len);
+		break;
+
+	case XFS_ILOG_DBROOT:
+		xfs_bmbt_to_bmdr(mp, (struct xfs_btree_block *)src, len,
+				 (xfs_bmdr_block_t *)XFS_DFORK_DPTR(dip),
+				 XFS_DFORK_DSIZE(dip, mp));
+		break;
+
+	default:
+		/*
+		 * There are no data fork flags set.
+		 */
+		ASSERT((fields & XFS_ILOG_DFORK) == 0);
+		break;
+	}
+
+	/*
+	 * If we logged any attribute data, recover it.  There may or
+	 * may not have been any other non-core data logged in this
+	 * transaction.
+	 */
+	if (in_f->ilf_fields & XFS_ILOG_AFORK) {
+		if (in_f->ilf_fields & XFS_ILOG_DFORK) {
+			attr_index = 3;
+		} else {
+			attr_index = 2;
+		}
+		len = item->ri_buf[attr_index].i_len;
+		src = item->ri_buf[attr_index].i_addr;
+		ASSERT(len == in_f->ilf_asize);
+
+		switch (in_f->ilf_fields & XFS_ILOG_AFORK) {
+		case XFS_ILOG_ADATA:
+		case XFS_ILOG_AEXT:
+			dest = XFS_DFORK_APTR(dip);
+			ASSERT(len <= XFS_DFORK_ASIZE(dip, mp));
+			memcpy(dest, src, len);
+			break;
+
+		case XFS_ILOG_ABROOT:
+			dest = XFS_DFORK_APTR(dip);
+			xfs_bmbt_to_bmdr(mp, (struct xfs_btree_block *)src,
+					 len, (xfs_bmdr_block_t*)dest,
+					 XFS_DFORK_ASIZE(dip, mp));
+			break;
+
+		default:
+			xfs_warn(log->l_mp, "%s: Invalid flag", __func__);
+			ASSERT(0);
+			xfs_buf_relse(bp);
+			error = EIO;
+			goto error;
+		}
+	}
+
+write_inode_buffer:
+	ASSERT(bp->b_target->bt_mount == mp);
+	bp->b_iodone = xlog_recover_iodone;
+	xfs_buf_delwri_queue(bp);
+	xfs_buf_relse(bp);
+error:
+	if (need_free)
+		kmem_free(in_f);
+	return XFS_ERROR(error);
+}
+
+/*
+ * Recover QUOTAOFF records. We simply make a note of it in the xlog_t
+ * structure, so that we know not to do any dquot item or dquot buffer recovery,
+ * of that type.
+ */
+STATIC int
+xlog_recover_quotaoff_pass1(
+	xlog_t			*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_qoff_logformat_t	*qoff_f = item->ri_buf[0].i_addr;
+	ASSERT(qoff_f);
+
+	/*
+	 * The logitem format's flag tells us if this was user quotaoff,
+	 * group/project quotaoff or both.
+	 */
+	if (qoff_f->qf_flags & XFS_UQUOTA_ACCT)
+		log->l_quotaoffs_flag |= XFS_DQ_USER;
+	if (qoff_f->qf_flags & XFS_PQUOTA_ACCT)
+		log->l_quotaoffs_flag |= XFS_DQ_PROJ;
+	if (qoff_f->qf_flags & XFS_GQUOTA_ACCT)
+		log->l_quotaoffs_flag |= XFS_DQ_GROUP;
+
+	return (0);
+}
+
+/*
+ * Recover a dquot record
+ */
+STATIC int
+xlog_recover_dquot_pass2(
+	xlog_t			*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_mount_t		*mp = log->l_mp;
+	xfs_buf_t		*bp;
+	struct xfs_disk_dquot	*ddq, *recddq;
+	int			error;
+	xfs_dq_logformat_t	*dq_f;
+	uint			type;
+
+
+	/*
+	 * Filesystems are required to send in quota flags at mount time.
+	 */
+	if (mp->m_qflags == 0)
+		return (0);
+
+	recddq = item->ri_buf[1].i_addr;
+	if (recddq == NULL) {
+		xfs_alert(log->l_mp, "NULL dquot in %s.", __func__);
+		return XFS_ERROR(EIO);
+	}
+	if (item->ri_buf[1].i_len < sizeof(xfs_disk_dquot_t)) {
+		xfs_alert(log->l_mp, "dquot too small (%d) in %s.",
+			item->ri_buf[1].i_len, __func__);
+		return XFS_ERROR(EIO);
+	}
+
+	/*
+	 * This type of quotas was turned off, so ignore this record.
+	 */
+	type = recddq->d_flags & (XFS_DQ_USER | XFS_DQ_PROJ | XFS_DQ_GROUP);
+	ASSERT(type);
+	if (log->l_quotaoffs_flag & type)
+		return (0);
+
+	/*
+	 * At this point we know that quota was _not_ turned off.
+	 * Since the mount flags are not indicating to us otherwise, this
+	 * must mean that quota is on, and the dquot needs to be replayed.
+	 * Remember that we may not have fully recovered the superblock yet,
+	 * so we can't do the usual trick of looking at the SB quota bits.
+	 *
+	 * The other possibility, of course, is that the quota subsystem was
+	 * removed since the last mount - ENOSYS.
+	 */
+	dq_f = item->ri_buf[0].i_addr;
+	ASSERT(dq_f);
+	error = xfs_qm_dqcheck(mp, recddq, dq_f->qlf_id, 0, XFS_QMOPT_DOWARN,
+			   "xlog_recover_dquot_pass2 (log copy)");
+	if (error)
+		return XFS_ERROR(EIO);
+	ASSERT(dq_f->qlf_len == 1);
+
+	error = xfs_read_buf(mp, mp->m_ddev_targp,
+			     dq_f->qlf_blkno,
+			     XFS_FSB_TO_BB(mp, dq_f->qlf_len),
+			     0, &bp);
+	if (error) {
+		xfs_buf_ioerror_alert(bp, "xlog_recover_do..(read#3)");
+		return error;
+	}
+	ASSERT(bp);
+	ddq = (xfs_disk_dquot_t *)xfs_buf_offset(bp, dq_f->qlf_boffset);
+
+	/*
+	 * At least the magic num portion should be on disk because this
+	 * was among a chunk of dquots created earlier, and we did some
+	 * minimal initialization then.
+	 */
+	error = xfs_qm_dqcheck(mp, ddq, dq_f->qlf_id, 0, XFS_QMOPT_DOWARN,
+			   "xlog_recover_dquot_pass2");
+	if (error) {
+		xfs_buf_relse(bp);
+		return XFS_ERROR(EIO);
+	}
+
+	memcpy(ddq, recddq, item->ri_buf[1].i_len);
+
+	ASSERT(dq_f->qlf_size == 2);
+	ASSERT(bp->b_target->bt_mount == mp);
+	bp->b_iodone = xlog_recover_iodone;
+	xfs_buf_delwri_queue(bp);
+	xfs_buf_relse(bp);
+
+	return (0);
+}
+
+/*
+ * This routine is called to create an in-core extent free intent
+ * item from the efi format structure which was logged on disk.
+ * It allocates an in-core efi, copies the extents from the format
+ * structure into it, and adds the efi to the AIL with the given
+ * LSN.
+ */
+STATIC int
+xlog_recover_efi_pass2(
+	xlog_t			*log,
+	xlog_recover_item_t	*item,
+	xfs_lsn_t		lsn)
+{
+	int			error;
+	xfs_mount_t		*mp = log->l_mp;
+	xfs_efi_log_item_t	*efip;
+	xfs_efi_log_format_t	*efi_formatp;
+
+	efi_formatp = item->ri_buf[0].i_addr;
+
+	efip = xfs_efi_init(mp, efi_formatp->efi_nextents);
+	if ((error = xfs_efi_copy_format(&(item->ri_buf[0]),
+					 &(efip->efi_format)))) {
+		xfs_efi_item_free(efip);
+		return error;
+	}
+	atomic_set(&efip->efi_next_extent, efi_formatp->efi_nextents);
+
+	spin_lock(&log->l_ailp->xa_lock);
+	/*
+	 * xfs_trans_ail_update() drops the AIL lock.
+	 */
+	xfs_trans_ail_update(log->l_ailp, &efip->efi_item, lsn);
+	return 0;
+}
+
+
+/*
+ * This routine is called when an efd format structure is found in
+ * a committed transaction in the log.  It's purpose is to cancel
+ * the corresponding efi if it was still in the log.  To do this
+ * it searches the AIL for the efi with an id equal to that in the
+ * efd format structure.  If we find it, we remove the efi from the
+ * AIL and free it.
+ */
+STATIC int
+xlog_recover_efd_pass2(
+	xlog_t			*log,
+	xlog_recover_item_t	*item)
+{
+	xfs_efd_log_format_t	*efd_formatp;
+	xfs_efi_log_item_t	*efip = NULL;
+	xfs_log_item_t		*lip;
+	__uint64_t		efi_id;
+	struct xfs_ail_cursor	cur;
+	struct xfs_ail		*ailp = log->l_ailp;
+
+	efd_formatp = item->ri_buf[0].i_addr;
+	ASSERT((item->ri_buf[0].i_len == (sizeof(xfs_efd_log_format_32_t) +
+		((efd_formatp->efd_nextents - 1) * sizeof(xfs_extent_32_t)))) ||
+	       (item->ri_buf[0].i_len == (sizeof(xfs_efd_log_format_64_t) +
+		((efd_formatp->efd_nextents - 1) * sizeof(xfs_extent_64_t)))));
+	efi_id = efd_formatp->efd_efi_id;
+
+	/*
+	 * Search for the efi with the id in the efd format structure
+	 * in the AIL.
+	 */
+	spin_lock(&ailp->xa_lock);
+	lip = xfs_trans_ail_cursor_first(ailp, &cur, 0);
+	while (lip != NULL) {
+		if (lip->li_type == XFS_LI_EFI) {
+			efip = (xfs_efi_log_item_t *)lip;
+			if (efip->efi_format.efi_id == efi_id) {
+				/*
+				 * xfs_trans_ail_delete() drops the
+				 * AIL lock.
+				 */
+				xfs_trans_ail_delete(ailp, lip);
+				xfs_efi_item_free(efip);
+				spin_lock(&ailp->xa_lock);
+				break;
+			}
+		}
+		lip = xfs_trans_ail_cursor_next(ailp, &cur);
+	}
+	xfs_trans_ail_cursor_done(ailp, &cur);
+	spin_unlock(&ailp->xa_lock);
+
+	return 0;
+}
+
+/*
+ * Free up any resources allocated by the transaction
+ *
+ * Remember that EFIs, EFDs, and IUNLINKs are handled later.
+ */
+STATIC void
+xlog_recover_free_trans(
+	struct xlog_recover	*trans)
+{
+	xlog_recover_item_t	*item, *n;
+	int			i;
+
+	list_for_each_entry_safe(item, n, &trans->r_itemq, ri_list) {
+		/* Free the regions in the item. */
+		list_del(&item->ri_list);
+		for (i = 0; i < item->ri_cnt; i++)
+			kmem_free(item->ri_buf[i].i_addr);
+		/* Free the item itself */
+		kmem_free(item->ri_buf);
+		kmem_free(item);
+	}
+	/* Free the transaction recover structure */
+	kmem_free(trans);
+}
+
+STATIC int
+xlog_recover_commit_pass1(
+	struct log		*log,
+	struct xlog_recover	*trans,
+	xlog_recover_item_t	*item)
+{
+	trace_xfs_log_recover_item_recover(log, trans, item, XLOG_RECOVER_PASS1);
+
+	switch (ITEM_TYPE(item)) {
+	case XFS_LI_BUF:
+		return xlog_recover_buffer_pass1(log, item);
+	case XFS_LI_QUOTAOFF:
+		return xlog_recover_quotaoff_pass1(log, item);
+	case XFS_LI_INODE:
+	case XFS_LI_EFI:
+	case XFS_LI_EFD:
+	case XFS_LI_DQUOT:
+		/* nothing to do in pass 1 */
+		return 0;
+	default:
+		xfs_warn(log->l_mp, "%s: invalid item type (%d)",
+			__func__, ITEM_TYPE(item));
+		ASSERT(0);
+		return XFS_ERROR(EIO);
+	}
+}
+
+STATIC int
+xlog_recover_commit_pass2(
+	struct log		*log,
+	struct xlog_recover	*trans,
+	xlog_recover_item_t	*item)
+{
+	trace_xfs_log_recover_item_recover(log, trans, item, XLOG_RECOVER_PASS2);
+
+	switch (ITEM_TYPE(item)) {
+	case XFS_LI_BUF:
+		return xlog_recover_buffer_pass2(log, item);
+	case XFS_LI_INODE:
+		return xlog_recover_inode_pass2(log, item);
+	case XFS_LI_EFI:
+		return xlog_recover_efi_pass2(log, item, trans->r_lsn);
+	case XFS_LI_EFD:
+		return xlog_recover_efd_pass2(log, item);
+	case XFS_LI_DQUOT:
+		return xlog_recover_dquot_pass2(log, item);
+	case XFS_LI_QUOTAOFF:
+		/* nothing to do in pass2 */
+		return 0;
+	default:
+		xfs_warn(log->l_mp, "%s: invalid item type (%d)",
+			__func__, ITEM_TYPE(item));
+		ASSERT(0);
+		return XFS_ERROR(EIO);
+	}
+}
+
+/*
+ * Perform the transaction.
+ *
+ * If the transaction modifies a buffer or inode, do it now.  Otherwise,
+ * EFIs and EFDs get queued up by adding entries into the AIL for them.
+ */
+STATIC int
+xlog_recover_commit_trans(
+	struct log		*log,
+	struct xlog_recover	*trans,
+	int			pass)
+{
+	int			error = 0;
+	xlog_recover_item_t	*item;
+
+	hlist_del(&trans->r_list);
+
+	error = xlog_recover_reorder_trans(log, trans, pass);
+	if (error)
+		return error;
+
+	list_for_each_entry(item, &trans->r_itemq, ri_list) {
+		if (pass == XLOG_RECOVER_PASS1)
+			error = xlog_recover_commit_pass1(log, trans, item);
+		else
+			error = xlog_recover_commit_pass2(log, trans, item);
+		if (error)
+			return error;
+	}
+
+	xlog_recover_free_trans(trans);
+	return 0;
+}
+
+STATIC int
+xlog_recover_unmount_trans(
+	struct log		*log,
+	xlog_recover_t		*trans)
+{
+	/* Do nothing now */
+	xfs_warn(log->l_mp, "%s: Unmount LR", __func__);
+	return 0;
+}
+
+/*
+ * There are two valid states of the r_state field.  0 indicates that the
+ * transaction structure is in a normal state.  We have either seen the
+ * start of the transaction or the last operation we added was not a partial
+ * operation.  If the last operation we added to the transaction was a
+ * partial operation, we need to mark r_state with XLOG_WAS_CONT_TRANS.
+ *
+ * NOTE: skip LRs with 0 data length.
+ */
+STATIC int
+xlog_recover_process_data(
+	xlog_t			*log,
+	struct hlist_head	rhash[],
+	xlog_rec_header_t	*rhead,
+	xfs_caddr_t		dp,
+	int			pass)
+{
+	xfs_caddr_t		lp;
+	int			num_logops;
+	xlog_op_header_t	*ohead;
+	xlog_recover_t		*trans;
+	xlog_tid_t		tid;
+	int			error;
+	unsigned long		hash;
+	uint			flags;
+
+	lp = dp + be32_to_cpu(rhead->h_len);
+	num_logops = be32_to_cpu(rhead->h_num_logops);
+
+	/* check the log format matches our own - else we can't recover */
+	if (xlog_header_check_recover(log->l_mp, rhead))
+		return (XFS_ERROR(EIO));
+
+	while ((dp < lp) && num_logops) {
+		ASSERT(dp + sizeof(xlog_op_header_t) <= lp);
+		ohead = (xlog_op_header_t *)dp;
+		dp += sizeof(xlog_op_header_t);
+		if (ohead->oh_clientid != XFS_TRANSACTION &&
+		    ohead->oh_clientid != XFS_LOG) {
+			xfs_warn(log->l_mp, "%s: bad clientid 0x%x",
+					__func__, ohead->oh_clientid);
+			ASSERT(0);
+			return (XFS_ERROR(EIO));
+		}
+		tid = be32_to_cpu(ohead->oh_tid);
+		hash = XLOG_RHASH(tid);
+		trans = xlog_recover_find_tid(&rhash[hash], tid);
+		if (trans == NULL) {		   /* not found; add new tid */
+			if (ohead->oh_flags & XLOG_START_TRANS)
+				xlog_recover_new_tid(&rhash[hash], tid,
+					be64_to_cpu(rhead->h_lsn));
+		} else {
+			if (dp + be32_to_cpu(ohead->oh_len) > lp) {
+				xfs_warn(log->l_mp, "%s: bad length 0x%x",
+					__func__, be32_to_cpu(ohead->oh_len));
+				WARN_ON(1);
+				return (XFS_ERROR(EIO));
+			}
+			flags = ohead->oh_flags & ~XLOG_END_TRANS;
+			if (flags & XLOG_WAS_CONT_TRANS)
+				flags &= ~XLOG_CONTINUE_TRANS;
+			switch (flags) {
+			case XLOG_COMMIT_TRANS:
+				error = xlog_recover_commit_trans(log,
+								trans, pass);
+				break;
+			case XLOG_UNMOUNT_TRANS:
+				error = xlog_recover_unmount_trans(log, trans);
+				break;
+			case XLOG_WAS_CONT_TRANS:
+				error = xlog_recover_add_to_cont_trans(log,
+						trans, dp,
+						be32_to_cpu(ohead->oh_len));
+				break;
+			case XLOG_START_TRANS:
+				xfs_warn(log->l_mp, "%s: bad transaction",
+					__func__);
+				ASSERT(0);
+				error = XFS_ERROR(EIO);
+				break;
+			case 0:
+			case XLOG_CONTINUE_TRANS:
+				error = xlog_recover_add_to_trans(log, trans,
+						dp, be32_to_cpu(ohead->oh_len));
+				break;
+			default:
+				xfs_warn(log->l_mp, "%s: bad flag 0x%x",
+					__func__, flags);
+				ASSERT(0);
+				error = XFS_ERROR(EIO);
+				break;
+			}
+			if (error)
+				return error;
+		}
+		dp += be32_to_cpu(ohead->oh_len);
+		num_logops--;
+	}
+	return 0;
+}
+
+/*
+ * Process an extent free intent item that was recovered from
+ * the log.  We need to free the extents that it describes.
+ */
+STATIC int
+xlog_recover_process_efi(
+	xfs_mount_t		*mp,
+	xfs_efi_log_item_t	*efip)
+{
+	xfs_efd_log_item_t	*efdp;
+	xfs_trans_t		*tp;
+	int			i;
+	int			error = 0;
+	xfs_extent_t		*extp;
+	xfs_fsblock_t		startblock_fsb;
+
+	ASSERT(!test_bit(XFS_EFI_RECOVERED, &efip->efi_flags));
+
+	/*
+	 * First check the validity of the extents described by the
+	 * EFI.  If any are bad, then assume that all are bad and
+	 * just toss the EFI.
+	 */
+	for (i = 0; i < efip->efi_format.efi_nextents; i++) {
+		extp = &(efip->efi_format.efi_extents[i]);
+		startblock_fsb = XFS_BB_TO_FSB(mp,
+				   XFS_FSB_TO_DADDR(mp, extp->ext_start));
+		if ((startblock_fsb == 0) ||
+		    (extp->ext_len == 0) ||
+		    (startblock_fsb >= mp->m_sb.sb_dblocks) ||
+		    (extp->ext_len >= mp->m_sb.sb_agblocks)) {
+			/*
+			 * This will pull the EFI from the AIL and
+			 * free the memory associated with it.
+			 */
+			xfs_efi_release(efip, efip->efi_format.efi_nextents);
+			return XFS_ERROR(EIO);
+		}
+	}
+
+	tp = xfs_trans_alloc(mp, 0);
+	error = xfs_trans_reserve(tp, 0, XFS_ITRUNCATE_LOG_RES(mp), 0, 0, 0);
+	if (error)
+		goto abort_error;
+	efdp = xfs_trans_get_efd(tp, efip, efip->efi_format.efi_nextents);
+
+	for (i = 0; i < efip->efi_format.efi_nextents; i++) {
+		extp = &(efip->efi_format.efi_extents[i]);
+		error = xfs_free_extent(tp, extp->ext_start, extp->ext_len);
+		if (error)
+			goto abort_error;
+		xfs_trans_log_efd_extent(tp, efdp, extp->ext_start,
+					 extp->ext_len);
+	}
+
+	set_bit(XFS_EFI_RECOVERED, &efip->efi_flags);
+	error = xfs_trans_commit(tp, 0);
+	return error;
+
+abort_error:
+	xfs_trans_cancel(tp, XFS_TRANS_ABORT);
+	return error;
+}
+
+/*
+ * When this is called, all of the EFIs which did not have
+ * corresponding EFDs should be in the AIL.  What we do now
+ * is free the extents associated with each one.
+ *
+ * Since we process the EFIs in normal transactions, they
+ * will be removed at some point after the commit.  This prevents
+ * us from just walking down the list processing each one.
+ * We'll use a flag in the EFI to skip those that we've already
+ * processed and use the AIL iteration mechanism's generation
+ * count to try to speed this up at least a bit.
+ *
+ * When we start, we know that the EFIs are the only things in
+ * the AIL.  As we process them, however, other items are added
+ * to the AIL.  Since everything added to the AIL must come after
+ * everything already in the AIL, we stop processing as soon as
+ * we see something other than an EFI in the AIL.
+ */
+STATIC int
+xlog_recover_process_efis(
+	xlog_t			*log)
+{
+	xfs_log_item_t		*lip;
+	xfs_efi_log_item_t	*efip;
+	int			error = 0;
+	struct xfs_ail_cursor	cur;
+	struct xfs_ail		*ailp;
+
+	ailp = log->l_ailp;
+	spin_lock(&ailp->xa_lock);
+	lip = xfs_trans_ail_cursor_first(ailp, &cur, 0);
+	while (lip != NULL) {
+		/*
+		 * We're done when we see something other than an EFI.
+		 * There should be no EFIs left in the AIL now.
+		 */
+		if (lip->li_type != XFS_LI_EFI) {
+#ifdef DEBUG
+			for (; lip; lip = xfs_trans_ail_cursor_next(ailp, &cur))
+				ASSERT(lip->li_type != XFS_LI_EFI);
+#endif
+			break;
+		}
+
+		/*
+		 * Skip EFIs that we've already processed.
+		 */
+		efip = (xfs_efi_log_item_t *)lip;
+		if (test_bit(XFS_EFI_RECOVERED, &efip->efi_flags)) {
+			lip = xfs_trans_ail_cursor_next(ailp, &cur);
+			continue;
+		}
+
+		spin_unlock(&ailp->xa_lock);
+		error = xlog_recover_process_efi(log->l_mp, efip);
+		spin_lock(&ailp->xa_lock);
+		if (error)
+			goto out;
+		lip = xfs_trans_ail_cursor_next(ailp, &cur);
+	}
+out:
+	xfs_trans_ail_cursor_done(ailp, &cur);
+	spin_unlock(&ailp->xa_lock);
+	return error;
+}
+
+/*
+ * This routine performs a transaction to null out a bad inode pointer
+ * in an agi unlinked inode hash bucket.
+ */
+STATIC void
+xlog_recover_clear_agi_bucket(
+	xfs_mount_t	*mp,
+	xfs_agnumber_t	agno,
+	int		bucket)
+{
+	xfs_trans_t	*tp;
+	xfs_agi_t	*agi;
+	xfs_buf_t	*agibp;
+	int		offset;
+	int		error;
+
+	tp = xfs_trans_alloc(mp, XFS_TRANS_CLEAR_AGI_BUCKET);
+	error = xfs_trans_reserve(tp, 0, XFS_CLEAR_AGI_BUCKET_LOG_RES(mp),
+				  0, 0, 0);
+	if (error)
+		goto out_abort;
+
+	error = xfs_read_agi(mp, tp, agno, &agibp);
+	if (error)
+		goto out_abort;
+
+	agi = XFS_BUF_TO_AGI(agibp);
+	agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
+	offset = offsetof(xfs_agi_t, agi_unlinked) +
+		 (sizeof(xfs_agino_t) * bucket);
+	xfs_trans_log_buf(tp, agibp, offset,
+			  (offset + sizeof(xfs_agino_t) - 1));
+
+	error = xfs_trans_commit(tp, 0);
+	if (error)
+		goto out_error;
+	return;
+
+out_abort:
+	xfs_trans_cancel(tp, XFS_TRANS_ABORT);
+out_error:
+	xfs_warn(mp, "%s: failed to clear agi %d. Continuing.", __func__, agno);
+	return;
+}
+
+STATIC xfs_agino_t
+xlog_recover_process_one_iunlink(
+	struct xfs_mount		*mp,
+	xfs_agnumber_t			agno,
+	xfs_agino_t			agino,
+	int				bucket)
+{
+	struct xfs_buf			*ibp;
+	struct xfs_dinode		*dip;
+	struct xfs_inode		*ip;
+	xfs_ino_t			ino;
+	int				error;
+
+	ino = XFS_AGINO_TO_INO(mp, agno, agino);
+	error = xfs_iget(mp, NULL, ino, 0, 0, &ip);
+	if (error)
+		goto fail;
+
+	/*
+	 * Get the on disk inode to find the next inode in the bucket.
+	 */
+	error = xfs_itobp(mp, NULL, ip, &dip, &ibp, XBF_LOCK);
+	if (error)
+		goto fail_iput;
+
+	ASSERT(ip->i_d.di_nlink == 0);
+	ASSERT(ip->i_d.di_mode != 0);
+
+	/* setup for the next pass */
+	agino = be32_to_cpu(dip->di_next_unlinked);
+	xfs_buf_relse(ibp);
+
+	/*
+	 * Prevent any DMAPI event from being sent when the reference on
+	 * the inode is dropped.
+	 */
+	ip->i_d.di_dmevmask = 0;
+
+	IRELE(ip);
+	return agino;
+
+ fail_iput:
+	IRELE(ip);
+ fail:
+	/*
+	 * We can't read in the inode this bucket points to, or this inode
+	 * is messed up.  Just ditch this bucket of inodes.  We will lose
+	 * some inodes and space, but at least we won't hang.
+	 *
+	 * Call xlog_recover_clear_agi_bucket() to perform a transaction to
+	 * clear the inode pointer in the bucket.
+	 */
+	xlog_recover_clear_agi_bucket(mp, agno, bucket);
+	return NULLAGINO;
+}
+
+/*
+ * xlog_iunlink_recover
+ *
+ * This is called during recovery to process any inodes which
+ * we unlinked but not freed when the system crashed.  These
+ * inodes will be on the lists in the AGI blocks.  What we do
+ * here is scan all the AGIs and fully truncate and free any
+ * inodes found on the lists.  Each inode is removed from the
+ * lists when it has been fully truncated and is freed.  The
+ * freeing of the inode and its removal from the list must be
+ * atomic.
+ */
+STATIC void
+xlog_recover_process_iunlinks(
+	xlog_t		*log)
+{
+	xfs_mount_t	*mp;
+	xfs_agnumber_t	agno;
+	xfs_agi_t	*agi;
+	xfs_buf_t	*agibp;
+	xfs_agino_t	agino;
+	int		bucket;
+	int		error;
+	uint		mp_dmevmask;
+
+	mp = log->l_mp;
+
+	/*
+	 * Prevent any DMAPI event from being sent while in this function.
+	 */
+	mp_dmevmask = mp->m_dmevmask;
+	mp->m_dmevmask = 0;
+
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		/*
+		 * Find the agi for this ag.
+		 */
+		error = xfs_read_agi(mp, NULL, agno, &agibp);
+		if (error) {
+			/*
+			 * AGI is b0rked. Don't process it.
+			 *
+			 * We should probably mark the filesystem as corrupt
+			 * after we've recovered all the ag's we can....
+			 */
+			continue;
+		}
+		/*
+		 * Unlock the buffer so that it can be acquired in the normal
+		 * course of the transaction to truncate and free each inode.
+		 * Because we are not racing with anyone else here for the AGI
+		 * buffer, we don't even need to hold it locked to read the
+		 * initial unlinked bucket entries out of the buffer. We keep
+		 * buffer reference though, so that it stays pinned in memory
+		 * while we need the buffer.
+		 */
+		agi = XFS_BUF_TO_AGI(agibp);
+		xfs_buf_unlock(agibp);
+
+		for (bucket = 0; bucket < XFS_AGI_UNLINKED_BUCKETS; bucket++) {
+			agino = be32_to_cpu(agi->agi_unlinked[bucket]);
+			while (agino != NULLAGINO) {
+				agino = xlog_recover_process_one_iunlink(mp,
+							agno, agino, bucket);
+			}
+		}
+		xfs_buf_rele(agibp);
+	}
+
+	mp->m_dmevmask = mp_dmevmask;
+}
+
+
+#ifdef DEBUG
+STATIC void
+xlog_pack_data_checksum(
+	xlog_t		*log,
+	xlog_in_core_t	*iclog,
+	int		size)
+{
+	int		i;
+	__be32		*up;
+	uint		chksum = 0;
+
+	up = (__be32 *)iclog->ic_datap;
+	/* divide length by 4 to get # words */
+	for (i = 0; i < (size >> 2); i++) {
+		chksum ^= be32_to_cpu(*up);
+		up++;
+	}
+	iclog->ic_header.h_chksum = cpu_to_be32(chksum);
+}
+#else
+#define xlog_pack_data_checksum(log, iclog, size)
+#endif
+
+/*
+ * Stamp cycle number in every block
+ */
+void
+xlog_pack_data(
+	xlog_t			*log,
+	xlog_in_core_t		*iclog,
+	int			roundoff)
+{
+	int			i, j, k;
+	int			size = iclog->ic_offset + roundoff;
+	__be32			cycle_lsn;
+	xfs_caddr_t		dp;
+
+	xlog_pack_data_checksum(log, iclog, size);
+
+	cycle_lsn = CYCLE_LSN_DISK(iclog->ic_header.h_lsn);
+
+	dp = iclog->ic_datap;
+	for (i = 0; i < BTOBB(size) &&
+		i < (XLOG_HEADER_CYCLE_SIZE / BBSIZE); i++) {
+		iclog->ic_header.h_cycle_data[i] = *(__be32 *)dp;
+		*(__be32 *)dp = cycle_lsn;
+		dp += BBSIZE;
+	}
+
+	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
+		xlog_in_core_2_t *xhdr = iclog->ic_data;
+
+		for ( ; i < BTOBB(size); i++) {
+			j = i / (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
+			k = i % (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
+			xhdr[j].hic_xheader.xh_cycle_data[k] = *(__be32 *)dp;
+			*(__be32 *)dp = cycle_lsn;
+			dp += BBSIZE;
+		}
+
+		for (i = 1; i < log->l_iclog_heads; i++) {
+			xhdr[i].hic_xheader.xh_cycle = cycle_lsn;
+		}
+	}
+}
+
+STATIC void
+xlog_unpack_data(
+	xlog_rec_header_t	*rhead,
+	xfs_caddr_t		dp,
+	xlog_t			*log)
+{
+	int			i, j, k;
+
+	for (i = 0; i < BTOBB(be32_to_cpu(rhead->h_len)) &&
+		  i < (XLOG_HEADER_CYCLE_SIZE / BBSIZE); i++) {
+		*(__be32 *)dp = *(__be32 *)&rhead->h_cycle_data[i];
+		dp += BBSIZE;
+	}
+
+	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
+		xlog_in_core_2_t *xhdr = (xlog_in_core_2_t *)rhead;
+		for ( ; i < BTOBB(be32_to_cpu(rhead->h_len)); i++) {
+			j = i / (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
+			k = i % (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
+			*(__be32 *)dp = xhdr[j].hic_xheader.xh_cycle_data[k];
+			dp += BBSIZE;
+		}
+	}
+}
+
+STATIC int
+xlog_valid_rec_header(
+	xlog_t			*log,
+	xlog_rec_header_t	*rhead,
+	xfs_daddr_t		blkno)
+{
+	int			hlen;
+
+	if (unlikely(rhead->h_magicno != cpu_to_be32(XLOG_HEADER_MAGIC_NUM))) {
+		XFS_ERROR_REPORT("xlog_valid_rec_header(1)",
+				XFS_ERRLEVEL_LOW, log->l_mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	if (unlikely(
+	    (!rhead->h_version ||
+	    (be32_to_cpu(rhead->h_version) & (~XLOG_VERSION_OKBITS))))) {
+		xfs_warn(log->l_mp, "%s: unrecognised log version (%d).",
+			__func__, be32_to_cpu(rhead->h_version));
+		return XFS_ERROR(EIO);
+	}
+
+	/* LR body must have data or it wouldn't have been written */
+	hlen = be32_to_cpu(rhead->h_len);
+	if (unlikely( hlen <= 0 || hlen > INT_MAX )) {
+		XFS_ERROR_REPORT("xlog_valid_rec_header(2)",
+				XFS_ERRLEVEL_LOW, log->l_mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	if (unlikely( blkno > log->l_logBBsize || blkno > INT_MAX )) {
+		XFS_ERROR_REPORT("xlog_valid_rec_header(3)",
+				XFS_ERRLEVEL_LOW, log->l_mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	return 0;
+}
+
+/*
+ * Read the log from tail to head and process the log records found.
+ * Handle the two cases where the tail and head are in the same cycle
+ * and where the active portion of the log wraps around the end of
+ * the physical log separately.  The pass parameter is passed through
+ * to the routines called to process the data and is not looked at
+ * here.
+ */
+STATIC int
+xlog_do_recovery_pass(
+	xlog_t			*log,
+	xfs_daddr_t		head_blk,
+	xfs_daddr_t		tail_blk,
+	int			pass)
+{
+	xlog_rec_header_t	*rhead;
+	xfs_daddr_t		blk_no;
+	xfs_caddr_t		offset;
+	xfs_buf_t		*hbp, *dbp;
+	int			error = 0, h_size;
+	int			bblks, split_bblks;
+	int			hblks, split_hblks, wrapped_hblks;
+	struct hlist_head	rhash[XLOG_RHASH_SIZE];
+
+	ASSERT(head_blk != tail_blk);
+
+	/*
+	 * Read the header of the tail block and get the iclog buffer size from
+	 * h_size.  Use this to tell how many sectors make up the log header.
+	 */
+	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
+		/*
+		 * When using variable length iclogs, read first sector of
+		 * iclog header and extract the header size from it.  Get a
+		 * new hbp that is the correct size.
+		 */
+		hbp = xlog_get_bp(log, 1);
+		if (!hbp)
+			return ENOMEM;
+
+		error = xlog_bread(log, tail_blk, 1, hbp, &offset);
+		if (error)
+			goto bread_err1;
+
+		rhead = (xlog_rec_header_t *)offset;
+		error = xlog_valid_rec_header(log, rhead, tail_blk);
+		if (error)
+			goto bread_err1;
+		h_size = be32_to_cpu(rhead->h_size);
+		if ((be32_to_cpu(rhead->h_version) & XLOG_VERSION_2) &&
+		    (h_size > XLOG_HEADER_CYCLE_SIZE)) {
+			hblks = h_size / XLOG_HEADER_CYCLE_SIZE;
+			if (h_size % XLOG_HEADER_CYCLE_SIZE)
+				hblks++;
+			xlog_put_bp(hbp);
+			hbp = xlog_get_bp(log, hblks);
+		} else {
+			hblks = 1;
+		}
+	} else {
+		ASSERT(log->l_sectBBsize == 1);
+		hblks = 1;
+		hbp = xlog_get_bp(log, 1);
+		h_size = XLOG_BIG_RECORD_BSIZE;
+	}
+
+	if (!hbp)
+		return ENOMEM;
+	dbp = xlog_get_bp(log, BTOBB(h_size));
+	if (!dbp) {
+		xlog_put_bp(hbp);
+		return ENOMEM;
+	}
+
+	memset(rhash, 0, sizeof(rhash));
+	if (tail_blk <= head_blk) {
+		for (blk_no = tail_blk; blk_no < head_blk; ) {
+			error = xlog_bread(log, blk_no, hblks, hbp, &offset);
+			if (error)
+				goto bread_err2;
+
+			rhead = (xlog_rec_header_t *)offset;
+			error = xlog_valid_rec_header(log, rhead, blk_no);
+			if (error)
+				goto bread_err2;
+
+			/* blocks in data section */
+			bblks = (int)BTOBB(be32_to_cpu(rhead->h_len));
+			error = xlog_bread(log, blk_no + hblks, bblks, dbp,
+					   &offset);
+			if (error)
+				goto bread_err2;
+
+			xlog_unpack_data(rhead, offset, log);
+			if ((error = xlog_recover_process_data(log,
+						rhash, rhead, offset, pass)))
+				goto bread_err2;
+			blk_no += bblks + hblks;
+		}
+	} else {
+		/*
+		 * Perform recovery around the end of the physical log.
+		 * When the head is not on the same cycle number as the tail,
+		 * we can't do a sequential recovery as above.
+		 */
+		blk_no = tail_blk;
+		while (blk_no < log->l_logBBsize) {
+			/*
+			 * Check for header wrapping around physical end-of-log
+			 */
+			offset = hbp->b_addr;
+			split_hblks = 0;
+			wrapped_hblks = 0;
+			if (blk_no + hblks <= log->l_logBBsize) {
+				/* Read header in one read */
+				error = xlog_bread(log, blk_no, hblks, hbp,
+						   &offset);
+				if (error)
+					goto bread_err2;
+			} else {
+				/* This LR is split across physical log end */
+				if (blk_no != log->l_logBBsize) {
+					/* some data before physical log end */
+					ASSERT(blk_no <= INT_MAX);
+					split_hblks = log->l_logBBsize - (int)blk_no;
+					ASSERT(split_hblks > 0);
+					error = xlog_bread(log, blk_no,
+							   split_hblks, hbp,
+							   &offset);
+					if (error)
+						goto bread_err2;
+				}
+
+				/*
+				 * Note: this black magic still works with
+				 * large sector sizes (non-512) only because:
+				 * - we increased the buffer size originally
+				 *   by 1 sector giving us enough extra space
+				 *   for the second read;
+				 * - the log start is guaranteed to be sector
+				 *   aligned;
+				 * - we read the log end (LR header start)
+				 *   _first_, then the log start (LR header end)
+				 *   - order is important.
+				 */
+				wrapped_hblks = hblks - split_hblks;
+				error = xlog_bread_offset(log, 0,
+						wrapped_hblks, hbp,
+						offset + BBTOB(split_hblks));
+				if (error)
+					goto bread_err2;
+			}
+			rhead = (xlog_rec_header_t *)offset;
+			error = xlog_valid_rec_header(log, rhead,
+						split_hblks ? blk_no : 0);
+			if (error)
+				goto bread_err2;
+
+			bblks = (int)BTOBB(be32_to_cpu(rhead->h_len));
+			blk_no += hblks;
+
+			/* Read in data for log record */
+			if (blk_no + bblks <= log->l_logBBsize) {
+				error = xlog_bread(log, blk_no, bblks, dbp,
+						   &offset);
+				if (error)
+					goto bread_err2;
+			} else {
+				/* This log record is split across the
+				 * physical end of log */
+				offset = dbp->b_addr;
+				split_bblks = 0;
+				if (blk_no != log->l_logBBsize) {
+					/* some data is before the physical
+					 * end of log */
+					ASSERT(!wrapped_hblks);
+					ASSERT(blk_no <= INT_MAX);
+					split_bblks =
+						log->l_logBBsize - (int)blk_no;
+					ASSERT(split_bblks > 0);
+					error = xlog_bread(log, blk_no,
+							split_bblks, dbp,
+							&offset);
+					if (error)
+						goto bread_err2;
+				}
+
+				/*
+				 * Note: this black magic still works with
+				 * large sector sizes (non-512) only because:
+				 * - we increased the buffer size originally
+				 *   by 1 sector giving us enough extra space
+				 *   for the second read;
+				 * - the log start is guaranteed to be sector
+				 *   aligned;
+				 * - we read the log end (LR header start)
+				 *   _first_, then the log start (LR header end)
+				 *   - order is important.
+				 */
+				error = xlog_bread_offset(log, 0,
+						bblks - split_bblks, hbp,
+						offset + BBTOB(split_bblks));
+				if (error)
+					goto bread_err2;
+			}
+			xlog_unpack_data(rhead, offset, log);
+			if ((error = xlog_recover_process_data(log, rhash,
+							rhead, offset, pass)))
+				goto bread_err2;
+			blk_no += bblks;
+		}
+
+		ASSERT(blk_no >= log->l_logBBsize);
+		blk_no -= log->l_logBBsize;
+
+		/* read first part of physical log */
+		while (blk_no < head_blk) {
+			error = xlog_bread(log, blk_no, hblks, hbp, &offset);
+			if (error)
+				goto bread_err2;
+
+			rhead = (xlog_rec_header_t *)offset;
+			error = xlog_valid_rec_header(log, rhead, blk_no);
+			if (error)
+				goto bread_err2;
+
+			bblks = (int)BTOBB(be32_to_cpu(rhead->h_len));
+			error = xlog_bread(log, blk_no+hblks, bblks, dbp,
+					   &offset);
+			if (error)
+				goto bread_err2;
+
+			xlog_unpack_data(rhead, offset, log);
+			if ((error = xlog_recover_process_data(log, rhash,
+							rhead, offset, pass)))
+				goto bread_err2;
+			blk_no += bblks + hblks;
+		}
+	}
+
+ bread_err2:
+	xlog_put_bp(dbp);
+ bread_err1:
+	xlog_put_bp(hbp);
+	return error;
+}
+
+/*
+ * Do the recovery of the log.  We actually do this in two phases.
+ * The two passes are necessary in order to implement the function
+ * of cancelling a record written into the log.  The first pass
+ * determines those things which have been cancelled, and the
+ * second pass replays log items normally except for those which
+ * have been cancelled.  The handling of the replay and cancellations
+ * takes place in the log item type specific routines.
+ *
+ * The table of items which have cancel records in the log is allocated
+ * and freed at this level, since only here do we know when all of
+ * the log recovery has been completed.
+ */
+STATIC int
+xlog_do_log_recovery(
+	xlog_t		*log,
+	xfs_daddr_t	head_blk,
+	xfs_daddr_t	tail_blk)
+{
+	int		error, i;
+
+	ASSERT(head_blk != tail_blk);
+
+	/*
+	 * First do a pass to find all of the cancelled buf log items.
+	 * Store them in the buf_cancel_table for use in the second pass.
+	 */
+	log->l_buf_cancel_table = kmem_zalloc(XLOG_BC_TABLE_SIZE *
+						 sizeof(struct list_head),
+						 KM_SLEEP);
+	for (i = 0; i < XLOG_BC_TABLE_SIZE; i++)
+		INIT_LIST_HEAD(&log->l_buf_cancel_table[i]);
+
+	error = xlog_do_recovery_pass(log, head_blk, tail_blk,
+				      XLOG_RECOVER_PASS1);
+	if (error != 0) {
+		kmem_free(log->l_buf_cancel_table);
+		log->l_buf_cancel_table = NULL;
+		return error;
+	}
+	/*
+	 * Then do a second pass to actually recover the items in the log.
+	 * When it is complete free the table of buf cancel items.
+	 */
+	error = xlog_do_recovery_pass(log, head_blk, tail_blk,
+				      XLOG_RECOVER_PASS2);
+#ifdef DEBUG
+	if (!error) {
+		int	i;
+
+		for (i = 0; i < XLOG_BC_TABLE_SIZE; i++)
+			ASSERT(list_empty(&log->l_buf_cancel_table[i]));
+	}
+#endif	/* DEBUG */
+
+	kmem_free(log->l_buf_cancel_table);
+	log->l_buf_cancel_table = NULL;
+
+	return error;
+}
+
+/*
+ * Do the actual recovery
+ */
+STATIC int
+xlog_do_recover(
+	xlog_t		*log,
+	xfs_daddr_t	head_blk,
+	xfs_daddr_t	tail_blk)
+{
+	int		error;
+	xfs_buf_t	*bp;
+	xfs_sb_t	*sbp;
+
+	/*
+	 * First replay the images in the log.
+	 */
+	error = xlog_do_log_recovery(log, head_blk, tail_blk);
+	if (error) {
+		return error;
+	}
+
+	xfs_flush_buftarg(log->l_mp->m_ddev_targp, 1);
+
+	/*
+	 * If IO errors happened during recovery, bail out.
+	 */
+	if (XFS_FORCED_SHUTDOWN(log->l_mp)) {
+		return (EIO);
+	}
+
+	/*
+	 * We now update the tail_lsn since much of the recovery has completed
+	 * and there may be space available to use.  If there were no extent
+	 * or iunlinks, we can free up the entire log and set the tail_lsn to
+	 * be the last_sync_lsn.  This was set in xlog_find_tail to be the
+	 * lsn of the last known good LR on disk.  If there are extent frees
+	 * or iunlinks they will have some entries in the AIL; so we look at
+	 * the AIL to determine how to set the tail_lsn.
+	 */
+	xlog_assign_tail_lsn(log->l_mp);
+
+	/*
+	 * Now that we've finished replaying all buffer and inode
+	 * updates, re-read in the superblock.
+	 */
+	bp = xfs_getsb(log->l_mp, 0);
+	XFS_BUF_UNDONE(bp);
+	ASSERT(!(XFS_BUF_ISWRITE(bp)));
+	ASSERT(!(XFS_BUF_ISDELAYWRITE(bp)));
+	XFS_BUF_READ(bp);
+	XFS_BUF_UNASYNC(bp);
+	xfsbdstrat(log->l_mp, bp);
+	error = xfs_buf_iowait(bp);
+	if (error) {
+		xfs_buf_ioerror_alert(bp, __func__);
+		ASSERT(0);
+		xfs_buf_relse(bp);
+		return error;
+	}
+
+	/* Convert superblock from on-disk format */
+	sbp = &log->l_mp->m_sb;
+	xfs_sb_from_disk(log->l_mp, XFS_BUF_TO_SBP(bp));
+	ASSERT(sbp->sb_magicnum == XFS_SB_MAGIC);
+	ASSERT(xfs_sb_good_version(sbp));
+	xfs_buf_relse(bp);
+
+	/* We've re-read the superblock so re-initialize per-cpu counters */
+	xfs_icsb_reinit_counters(log->l_mp);
+
+	xlog_recover_check_summary(log);
+
+	/* Normal transactions can now occur */
+	log->l_flags &= ~XLOG_ACTIVE_RECOVERY;
+	return 0;
+}
+
+/*
+ * Perform recovery and re-initialize some log variables in xlog_find_tail.
+ *
+ * Return error or zero.
+ */
+int
+xlog_recover(
+	xlog_t		*log)
+{
+	xfs_daddr_t	head_blk, tail_blk;
+	int		error;
+
+	/* find the tail of the log */
+	if ((error = xlog_find_tail(log, &head_blk, &tail_blk)))
+		return error;
+
+	if (tail_blk != head_blk) {
+		/* There used to be a comment here:
+		 *
+		 * disallow recovery on read-only mounts.  note -- mount
+		 * checks for ENOSPC and turns it into an intelligent
+		 * error message.
+		 * ...but this is no longer true.  Now, unless you specify
+		 * NORECOVERY (in which case this function would never be
+		 * called), we just go ahead and recover.  We do this all
+		 * under the vfs layer, so we can get away with it unless
+		 * the device itself is read-only, in which case we fail.
+		 */
+		if ((error = xfs_dev_is_read_only(log->l_mp, "recovery"))) {
+			return error;
+		}
+
+		xfs_notice(log->l_mp, "Starting recovery (logdev: %s)",
+				log->l_mp->m_logname ? log->l_mp->m_logname
+						     : "internal");
+
+		error = xlog_do_recover(log, head_blk, tail_blk);
+		log->l_flags |= XLOG_RECOVERY_NEEDED;
+	}
+	return error;
+}
+
+/*
+ * In the first part of recovery we replay inodes and buffers and build
+ * up the list of extent free items which need to be processed.  Here
+ * we process the extent free items and clean up the on disk unlinked
+ * inode lists.  This is separated from the first part of recovery so
+ * that the root and real-time bitmap inodes can be read in from disk in
+ * between the two stages.  This is necessary so that we can free space
+ * in the real-time portion of the file system.
+ */
+int
+xlog_recover_finish(
+	xlog_t		*log)
+{
+	/*
+	 * Now we're ready to do the transactions needed for the
+	 * rest of recovery.  Start with completing all the extent
+	 * free intent records and then process the unlinked inode
+	 * lists.  At this point, we essentially run in normal mode
+	 * except that we're still performing recovery actions
+	 * rather than accepting new requests.
+	 */
+	if (log->l_flags & XLOG_RECOVERY_NEEDED) {
+		int	error;
+		error = xlog_recover_process_efis(log);
+		if (error) {
+			xfs_alert(log->l_mp, "Failed to recover EFIs");
+			return error;
+		}
+		/*
+		 * Sync the log to get all the EFIs out of the AIL.
+		 * This isn't absolutely necessary, but it helps in
+		 * case the unlink transactions would have problems
+		 * pushing the EFIs out of the way.
+		 */
+		xfs_log_force(log->l_mp, XFS_LOG_SYNC);
+
+		xlog_recover_process_iunlinks(log);
+
+		xlog_recover_check_summary(log);
+
+		xfs_notice(log->l_mp, "Ending recovery (logdev: %s)",
+				log->l_mp->m_logname ? log->l_mp->m_logname
+						     : "internal");
+		log->l_flags &= ~XLOG_RECOVERY_NEEDED;
+	} else {
+		xfs_info(log->l_mp, "Ending clean mount");
+	}
+	return 0;
+}
+
+
+#if defined(DEBUG)
+/*
+ * Read all of the agf and agi counters and check that they
+ * are consistent with the superblock counters.
+ */
+void
+xlog_recover_check_summary(
+	xlog_t		*log)
+{
+	xfs_mount_t	*mp;
+	xfs_agf_t	*agfp;
+	xfs_buf_t	*agfbp;
+	xfs_buf_t	*agibp;
+	xfs_agnumber_t	agno;
+	__uint64_t	freeblks;
+	__uint64_t	itotal;
+	__uint64_t	ifree;
+	int		error;
+
+	mp = log->l_mp;
+
+	freeblks = 0LL;
+	itotal = 0LL;
+	ifree = 0LL;
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		error = xfs_read_agf(mp, NULL, agno, 0, &agfbp);
+		if (error) {
+			xfs_alert(mp, "%s agf read failed agno %d error %d",
+						__func__, agno, error);
+		} else {
+			agfp = XFS_BUF_TO_AGF(agfbp);
+			freeblks += be32_to_cpu(agfp->agf_freeblks) +
+				    be32_to_cpu(agfp->agf_flcount);
+			xfs_buf_relse(agfbp);
+		}
+
+		error = xfs_read_agi(mp, NULL, agno, &agibp);
+		if (error) {
+			xfs_alert(mp, "%s agi read failed agno %d error %d",
+						__func__, agno, error);
+		} else {
+			struct xfs_agi	*agi = XFS_BUF_TO_AGI(agibp);
+
+			itotal += be32_to_cpu(agi->agi_count);
+			ifree += be32_to_cpu(agi->agi_freecount);
+			xfs_buf_relse(agibp);
+		}
+	}
+}
+#endif /* DEBUG */