// SPDX-License-Identifier: GPL-2.0

  /*

   * Copyright (c) 2000-2006 Silicon Graphics, Inc.

   * All Rights Reserved.

   */

  #include "xfs.h"

  #include "xfs_fs.h"

  #include "xfs_shared.h"

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

  #include "xfs_bit.h"

  #include "xfs_sb.h"

  #include "xfs_mount.h"

  #include "xfs_defer.h"

  #include "xfs_inode.h"

  #include "xfs_trans.h"

  #include "xfs_log.h"

  #include "xfs_log_priv.h"

  #include "xfs_log_recover.h"

  #include "xfs_trans_priv.h"

  #include "xfs_alloc.h"
  #include "xfs_ialloc.h"

  #include "xfs_trace.h"

  #include "xfs_icache.h"

  #include "xfs_error.h"

  #include "xfs_buf_item.h"

  #define BLK_AVG(blk1, blk2)	((blk1+blk2) >> 1)

  STATIC int
  xlog_find_zeroed(
  	struct xlog	*,
  	xfs_daddr_t	*);
  STATIC int
  xlog_clear_stale_blocks(
  	struct xlog	*,
  	xfs_lsn_t);

  #if defined(DEBUG)

  STATIC void
  xlog_recover_check_summary(
  	struct xlog *);

  #else
  #define	xlog_recover_check_summary(log)

  #endif

  STATIC int
  xlog_do_recovery_pass(
          struct xlog *, xfs_daddr_t, xfs_daddr_t, int, xfs_daddr_t *);

  /*
   * Sector aligned buffer routines for buffer create/read/write/access
   */

  /*

   * Verify the log-relative block number and length in basic blocks are valid for
   * an operation involving the given XFS log buffer. Returns true if the fields
   * are valid, false otherwise.

   */

  static inline bool

  xlog_verify_bno(

  	struct xlog	*log,

  	xfs_daddr_t	blk_no,

  	int		bbcount)
  {

  	if (blk_no < 0 || blk_no >= log->l_logBBsize)
  		return false;
  	if (bbcount <= 0 || (blk_no + bbcount) > log->l_logBBsize)
  		return false;
  	return true;

  }

  /*

   * 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 offset within the log.

   */

  static char *

  xlog_alloc_buffer(

  	struct xlog	*log,

  	int		nbblks)

  {

  	int align_mask = xfs_buftarg_dma_alignment(log->l_targ);

  	/*
  	 * Pass log block 0 since we don't have an addr yet, buffer will be
  	 * verified on read.
  	 */

  	if (XFS_IS_CORRUPT(log->l_mp, !xlog_verify_bno(log, 0, nbblks))) {

  		xfs_warn(log->l_mp, "Invalid block length (0x%x) for buffer",

  			nbblks);

  		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);

  	return kmem_alloc_io(BBTOB(nbblks), align_mask, KM_MAYFAIL | KM_ZERO);

  }

  /*
   * 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 inline unsigned int

  xlog_align(

  	struct xlog	*log,

  	xfs_daddr_t	blk_no)

  {

  	return BBTOB(blk_no & ((xfs_daddr_t)log->l_sectBBsize - 1));

  }

  static int
  xlog_do_io(
  	struct xlog		*log,
  	xfs_daddr_t		blk_no,
  	unsigned int		nbblks,
  	char			*data,
  	unsigned int		op)

  {

  	int			error;

  	if (XFS_IS_CORRUPT(log->l_mp, !xlog_verify_bno(log, blk_no, nbblks))) {

  		xfs_warn(log->l_mp,
  			 "Invalid log block/length (0x%llx, 0x%x) for buffer",
  			 blk_no, nbblks);

  		return -EFSCORRUPTED;

  	}

  	blk_no = round_down(blk_no, log->l_sectBBsize);
  	nbblks = round_up(nbblks, log->l_sectBBsize);

  	ASSERT(nbblks > 0);

  	error = xfs_rw_bdev(log->l_targ->bt_bdev, log->l_logBBstart + blk_no,
  			BBTOB(nbblks), data, op);
  	if (error && !XFS_FORCED_SHUTDOWN(log->l_mp)) {
  		xfs_alert(log->l_mp,
  			  "log recovery %s I/O error at daddr 0x%llx len %d error %d",
  			  op == REQ_OP_WRITE ? "write" : "read",
  			  blk_no, nbblks, error);
  	}

  	return error;
  }

  STATIC int

  xlog_bread_noalign(

  	struct xlog	*log,

  	xfs_daddr_t	blk_no,
  	int		nbblks,

  	char		*data)

  {

  	return xlog_do_io(log, blk_no, nbblks, data, REQ_OP_READ);

  }

  STATIC int

  xlog_bread(

  	struct xlog	*log,

  	xfs_daddr_t	blk_no,
  	int		nbblks,
  	char		*data,
  	char		**offset)

  {

  	int		error;

  	error = xlog_do_io(log, blk_no, nbblks, data, REQ_OP_READ);
  	if (!error)
  		*offset = data + xlog_align(log, blk_no);
  	return error;

  }

  STATIC int

  xlog_bwrite(

  	struct xlog	*log,

  	xfs_daddr_t	blk_no,
  	int		nbblks,

  	char		*data)

  {

  	return xlog_do_io(log, blk_no, nbblks, data, REQ_OP_WRITE);

  }

  #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",

  		__func__, &mp->m_sb.sb_uuid, XLOG_FMT);

  	xfs_debug(mp, "    log : uuid = %pU, fmt = %d",

  		&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 (XFS_IS_CORRUPT(mp, 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);

  		return -EFSCORRUPTED;

  	}
  	if (XFS_IS_CORRUPT(mp, !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);

  		return -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_null(&head->h_fs_uuid)) {

  		/*
  		 * IRIX doesn't write the h_fs_uuid or h_fmt fields. If

  		 * h_fs_uuid is null, we assume this log was last mounted

  		 * by IRIX and continue.
  		 */

  		xfs_warn(mp, "null uuid in log - IRIX style log");

  	} else if (XFS_IS_CORRUPT(mp, !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);

  		return -EFSCORRUPTED;

  	}
  	return 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(

  	struct xlog	*log,

  	char		*buffer,

  	xfs_daddr_t	first_blk,
  	xfs_daddr_t	*last_blk,
  	uint		cycle)
  {

  	char		*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, buffer, &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(

  	struct xlog	*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;

  	char		*buffer;

  	xfs_daddr_t	bufblks;

  	char		*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 (bufblks > log->l_logBBsize)
  		bufblks >>= 1;

  	while (!(buffer = xlog_alloc_buffer(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, buffer, &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:

  	kmem_free(buffer);

  	return error;
  }

  static inline int
  xlog_logrec_hblks(struct xlog *log, struct xlog_rec_header *rh)
  {
  	if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
  		int	h_size = be32_to_cpu(rh->h_size);
  
  		if ((be32_to_cpu(rh->h_version) & XLOG_VERSION_2) &&
  		    h_size > XLOG_HEADER_CYCLE_SIZE)
  			return DIV_ROUND_UP(h_size, XLOG_HEADER_CYCLE_SIZE);
  	}
  	return 1;
  }

  /*
   * 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(

  	struct xlog		*log,

  	xfs_daddr_t		start_blk,
  	xfs_daddr_t		*last_blk,
  	int			extra_bblks)
  {
  	xfs_daddr_t		i;

  	char			*buffer;

  	char			*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);

  	buffer = xlog_alloc_buffer(log, num_blks);
  	if (!buffer) {
  		buffer = xlog_alloc_buffer(log, 1);
  		if (!buffer)

  			return -ENOMEM;

  		smallmem = 1;
  	} else {

  		error = xlog_bread(log, start_blk, num_blks, buffer, &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 = -EFSCORRUPTED;

  			goto out;
  		}
  
  		if (smallmem) {

  			error = xlog_bread(log, i, 1, buffer, &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.
  	 */

  	xhdrs = xlog_logrec_hblks(log, head);

  	if (*last_blk - i + extra_bblks !=
  	    BTOBB(be32_to_cpu(head->h_len)) + xhdrs)

  		*last_blk = i;
  
  out:

  	kmem_free(buffer);

  	return error;
  }
  
  /*
   * Head is defined to be the point of the log where the next log 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(

  	struct xlog	*log,

  	xfs_daddr_t	*return_head_blk)
  {

  	char		*buffer;

  	char		*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? */

  	error = xlog_find_zeroed(log, &first_blk);
  	if (error < 0) {
  		xfs_warn(log->l_mp, "empty log check failed");
  		return error;
  	}
  	if (error == 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;

  	}
  
  	first_blk = 0;			/* get cycle # of 1st block */

  	buffer = xlog_alloc_buffer(log, 1);
  	if (!buffer)

  		return -ENOMEM;

  	error = xlog_bread(log, 0, 1, buffer, &offset);

  	if (error)

  		goto out_free_buffer;

  	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, buffer, &offset);

  	if (error)

  		goto out_free_buffer;

  	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;

  		error = xlog_find_cycle_start(log, buffer, first_blk, &head_blk,
  				last_half_cycle);
  		if (error)
  			goto out_free_buffer;

  	}
  
  	/*
  	 * 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 = min_t(int, log_bbnum, 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 out_free_buffer;

  		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 out_free_buffer;

  		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 out_free_buffer;

  		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 */

  		error = xlog_find_verify_log_record(log, start_blk, &head_blk, 0);
  		if (error == 1)
  			error = -EIO;
  		if (error)

  			goto out_free_buffer;

  	} else {
  		start_blk = 0;
  		ASSERT(head_blk <= INT_MAX);

  		error = xlog_find_verify_log_record(log, start_blk, &head_blk, 0);
  		if (error < 0)

  			goto out_free_buffer;

  		if (error == 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);

  			error = xlog_find_verify_log_record(log, start_blk,
  							&new_blk, (int)head_blk);
  			if (error == 1)
  				error = -EIO;
  			if (error)

  				goto out_free_buffer;

  			if (new_blk != log_bbnum)
  				head_blk = new_blk;
  		} else if (error)

  			goto out_free_buffer;

  	}

  	kmem_free(buffer);

  	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;

  out_free_buffer:
  	kmem_free(buffer);

  	if (error)

  		xfs_warn(log->l_mp, "failed to find log head");

  	return error;
  }
  
  /*

   * Seek backwards in the log for log record headers.
   *
   * Given a starting log block, walk backwards until we find the provided number
   * of records or hit the provided tail block. The return value is the number of
   * records encountered or a negative error code. The log block and buffer
   * pointer of the last record seen are returned in rblk and rhead respectively.
   */
  STATIC int
  xlog_rseek_logrec_hdr(
  	struct xlog		*log,
  	xfs_daddr_t		head_blk,
  	xfs_daddr_t		tail_blk,
  	int			count,

  	char			*buffer,

  	xfs_daddr_t		*rblk,
  	struct xlog_rec_header	**rhead,
  	bool			*wrapped)
  {
  	int			i;
  	int			error;
  	int			found = 0;
  	char			*offset = NULL;
  	xfs_daddr_t		end_blk;
  
  	*wrapped = false;
  
  	/*
  	 * Walk backwards from the head block until we hit the tail or the first
  	 * block in the log.
  	 */
  	end_blk = head_blk > tail_blk ? tail_blk : 0;
  	for (i = (int) head_blk - 1; i >= end_blk; i--) {

  		error = xlog_bread(log, i, 1, buffer, &offset);

  		if (error)
  			goto out_error;
  
  		if (*(__be32 *) offset == cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
  			*rblk = i;
  			*rhead = (struct xlog_rec_header *) offset;
  			if (++found == count)
  				break;
  		}
  	}
  
  	/*
  	 * If we haven't hit the tail block or the log record header count,
  	 * start looking again from the end of the physical log. Note that
  	 * callers can pass head == tail if the tail is not yet known.
  	 */
  	if (tail_blk >= head_blk && found != count) {
  		for (i = log->l_logBBsize - 1; i >= (int) tail_blk; i--) {

  			error = xlog_bread(log, i, 1, buffer, &offset);

  			if (error)
  				goto out_error;
  
  			if (*(__be32 *)offset ==
  			    cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
  				*wrapped = true;
  				*rblk = i;
  				*rhead = (struct xlog_rec_header *) offset;
  				if (++found == count)
  					break;
  			}
  		}
  	}
  
  	return found;
  
  out_error:
  	return error;
  }
  
  /*

   * Seek forward in the log for log record headers.
   *
   * Given head and tail blocks, walk forward from the tail block until we find
   * the provided number of records or hit the head block. The return value is the
   * number of records encountered or a negative error code. The log block and
   * buffer pointer of the last record seen are returned in rblk and rhead
   * respectively.
   */
  STATIC int
  xlog_seek_logrec_hdr(
  	struct xlog		*log,
  	xfs_daddr_t		head_blk,
  	xfs_daddr_t		tail_blk,
  	int			count,

  	char			*buffer,

  	xfs_daddr_t		*rblk,
  	struct xlog_rec_header	**rhead,
  	bool			*wrapped)
  {
  	int			i;
  	int			error;
  	int			found = 0;
  	char			*offset = NULL;
  	xfs_daddr_t		end_blk;
  
  	*wrapped = false;
  
  	/*
  	 * Walk forward from the tail block until we hit the head or the last
  	 * block in the log.
  	 */
  	end_blk = head_blk > tail_blk ? head_blk : log->l_logBBsize - 1;
  	for (i = (int) tail_blk; i <= end_blk; i++) {

  		error = xlog_bread(log, i, 1, buffer, &offset);

  		if (error)
  			goto out_error;
  
  		if (*(__be32 *) offset == cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
  			*rblk = i;
  			*rhead = (struct xlog_rec_header *) offset;
  			if (++found == count)
  				break;
  		}
  	}
  
  	/*
  	 * If we haven't hit the head block or the log record header count,
  	 * start looking again from the start of the physical log.
  	 */
  	if (tail_blk > head_blk && found != count) {
  		for (i = 0; i < (int) head_blk; i++) {

  			error = xlog_bread(log, i, 1, buffer, &offset);

  			if (error)
  				goto out_error;
  
  			if (*(__be32 *)offset ==
  			    cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) {
  				*wrapped = true;
  				*rblk = i;
  				*rhead = (struct xlog_rec_header *) offset;
  				if (++found == count)
  					break;
  			}
  		}
  	}
  
  	return found;
  
  out_error:
  	return error;
  }
  
  /*

   * Calculate distance from head to tail (i.e., unused space in the log).
   */
  static inline int
  xlog_tail_distance(
  	struct xlog	*log,
  	xfs_daddr_t	head_blk,
  	xfs_daddr_t	tail_blk)
  {
  	if (head_blk < tail_blk)
  		return tail_blk - head_blk;
  
  	return tail_blk + (log->l_logBBsize - head_blk);
  }
  
  /*
   * Verify the log tail. This is particularly important when torn or incomplete
   * writes have been detected near the front of the log and the head has been
   * walked back accordingly.
   *
   * We also have to handle the case where the tail was pinned and the head
   * blocked behind the tail right before a crash. If the tail had been pushed
   * immediately prior to the crash and the subsequent checkpoint was only
   * partially written, it's possible it overwrote the last referenced tail in the
   * log with garbage. This is not a coherency problem because the tail must have
   * been pushed before it can be overwritten, but appears as log corruption to
   * recovery because we have no way to know the tail was updated if the
   * subsequent checkpoint didn't write successfully.

   *

   * Therefore, CRC check the log from tail to head. If a failure occurs and the
   * offending record is within max iclog bufs from the head, walk the tail
   * forward and retry until a valid tail is found or corruption is detected out
   * of the range of a possible overwrite.

   */
  STATIC int
  xlog_verify_tail(
  	struct xlog		*log,
  	xfs_daddr_t		head_blk,

  	xfs_daddr_t		*tail_blk,
  	int			hsize)

  {
  	struct xlog_rec_header	*thead;

  	char			*buffer;

  	xfs_daddr_t		first_bad;

  	int			error = 0;
  	bool			wrapped;

  	xfs_daddr_t		tmp_tail;
  	xfs_daddr_t		orig_tail = *tail_blk;

  	buffer = xlog_alloc_buffer(log, 1);
  	if (!buffer)

  		return -ENOMEM;
  
  	/*

  	 * Make sure the tail points to a record (returns positive count on
  	 * success).

  	 */

  	error = xlog_seek_logrec_hdr(log, head_blk, *tail_blk, 1, buffer,

  			&tmp_tail, &thead, &wrapped);
  	if (error < 0)

  		goto out;

  	if (*tail_blk != tmp_tail)
  		*tail_blk = tmp_tail;

  
  	/*

  	 * Run a CRC check from the tail to the head. We can't just check
  	 * MAX_ICLOGS records past the tail because the tail may point to stale
  	 * blocks cleared during the search for the head/tail. These blocks are
  	 * overwritten with zero-length records and thus record count is not a
  	 * reliable indicator of the iclog state before a crash.

  	 */

  	first_bad = 0;
  	error = xlog_do_recovery_pass(log, head_blk, *tail_blk,

  				      XLOG_RECOVER_CRCPASS, &first_bad);

  	while ((error == -EFSBADCRC || error == -EFSCORRUPTED) && first_bad) {

  		int	tail_distance;
  
  		/*
  		 * Is corruption within range of the head? If so, retry from
  		 * the next record. Otherwise return an error.
  		 */
  		tail_distance = xlog_tail_distance(log, head_blk, first_bad);
  		if (tail_distance > BTOBB(XLOG_MAX_ICLOGS * hsize))
  			break;

  		/* skip to the next record; returns positive count on success */

  		error = xlog_seek_logrec_hdr(log, head_blk, first_bad, 2,
  				buffer, &tmp_tail, &thead, &wrapped);

  		if (error < 0)
  			goto out;
  
  		*tail_blk = tmp_tail;
  		first_bad = 0;
  		error = xlog_do_recovery_pass(log, head_blk, *tail_blk,
  					      XLOG_RECOVER_CRCPASS, &first_bad);
  	}
  
  	if (!error && *tail_blk != orig_tail)
  		xfs_warn(log->l_mp,
  		"Tail block (0x%llx) overwrite detected. Updated to 0x%llx",
  			 orig_tail, *tail_blk);

  out:

  	kmem_free(buffer);

  	return error;
  }
  
  /*
   * Detect and trim torn writes from the head of the log.
   *
   * Storage without sector atomicity guarantees can result in torn writes in the
   * log in the event of a crash. Our only means to detect this scenario is via
   * CRC verification. While we can't always be certain that CRC verification
   * failure is due to a torn write vs. an unrelated corruption, we do know that
   * only a certain number (XLOG_MAX_ICLOGS) of log records can be written out at
   * one time. Therefore, CRC verify up to XLOG_MAX_ICLOGS records at the head of
   * the log and treat failures in this range as torn writes as a matter of
   * policy. In the event of CRC failure, the head is walked back to the last good
   * record in the log and the tail is updated from that record and verified.
   */
  STATIC int
  xlog_verify_head(
  	struct xlog		*log,
  	xfs_daddr_t		*head_blk,	/* in/out: unverified head */
  	xfs_daddr_t		*tail_blk,	/* out: tail block */

  	char			*buffer,

  	xfs_daddr_t		*rhead_blk,	/* start blk of last record */
  	struct xlog_rec_header	**rhead,	/* ptr to last record */
  	bool			*wrapped)	/* last rec. wraps phys. log */
  {
  	struct xlog_rec_header	*tmp_rhead;

  	char			*tmp_buffer;

  	xfs_daddr_t		first_bad;
  	xfs_daddr_t		tmp_rhead_blk;
  	int			found;
  	int			error;
  	bool			tmp_wrapped;
  
  	/*

  	 * Check the head of the log for torn writes. Search backwards from the
  	 * head until we hit the tail or the maximum number of log record I/Os
  	 * that could have been in flight at one time. Use a temporary buffer so

  	 * we don't trash the rhead/buffer pointers from the caller.

  	 */

  	tmp_buffer = xlog_alloc_buffer(log, 1);
  	if (!tmp_buffer)

  		return -ENOMEM;
  	error = xlog_rseek_logrec_hdr(log, *head_blk, *tail_blk,

  				      XLOG_MAX_ICLOGS, tmp_buffer,
  				      &tmp_rhead_blk, &tmp_rhead, &tmp_wrapped);
  	kmem_free(tmp_buffer);

  	if (error < 0)
  		return error;
  
  	/*
  	 * Now run a CRC verification pass over the records starting at the
  	 * block found above to the current head. If a CRC failure occurs, the
  	 * log block of the first bad record is saved in first_bad.
  	 */
  	error = xlog_do_recovery_pass(log, *head_blk, tmp_rhead_blk,
  				      XLOG_RECOVER_CRCPASS, &first_bad);

  	if ((error == -EFSBADCRC || error == -EFSCORRUPTED) && first_bad) {

  		/*
  		 * We've hit a potential torn write. Reset the error and warn
  		 * about it.
  		 */
  		error = 0;
  		xfs_warn(log->l_mp,
  "Torn write (CRC failure) detected at log block 0x%llx. Truncating head block from 0x%llx.",
  			 first_bad, *head_blk);
  
  		/*
  		 * Get the header block and buffer pointer for the last good
  		 * record before the bad record.
  		 *
  		 * Note that xlog_find_tail() clears the blocks at the new head
  		 * (i.e., the records with invalid CRC) if the cycle number

  		 * matches the current cycle.

  		 */

  		found = xlog_rseek_logrec_hdr(log, first_bad, *tail_blk, 1,
  				buffer, rhead_blk, rhead, wrapped);

  		if (found < 0)
  			return found;
  		if (found == 0)		/* XXX: right thing to do here? */
  			return -EIO;
  
  		/*
  		 * Reset the head block to the starting block of the first bad
  		 * log record and set the tail block based on the last good
  		 * record.
  		 *
  		 * Bail out if the updated head/tail match as this indicates
  		 * possible corruption outside of the acceptable
  		 * (XLOG_MAX_ICLOGS) range. This is a job for xfs_repair...
  		 */
  		*head_blk = first_bad;
  		*tail_blk = BLOCK_LSN(be64_to_cpu((*rhead)->h_tail_lsn));
  		if (*head_blk == *tail_blk) {
  			ASSERT(0);
  			return 0;
  		}

  	}

  	if (error)
  		return error;

  	return xlog_verify_tail(log, *head_blk, tail_blk,
  				be32_to_cpu((*rhead)->h_size));

  }
  
  /*

   * We need to make sure we handle log wrapping properly, so we can't use the
   * calculated logbno directly. Make sure it wraps to the correct bno inside the
   * log.
   *
   * The log is limited to 32 bit sizes, so we use the appropriate modulus
   * operation here and cast it back to a 64 bit daddr on return.
   */
  static inline xfs_daddr_t
  xlog_wrap_logbno(
  	struct xlog		*log,
  	xfs_daddr_t		bno)
  {
  	int			mod;
  
  	div_s64_rem(bno, log->l_logBBsize, &mod);
  	return mod;
  }
  
  /*

   * Check whether the head of the log points to an unmount record. In other
   * words, determine whether the log is clean. If so, update the in-core state
   * appropriately.
   */
  static int
  xlog_check_unmount_rec(
  	struct xlog		*log,
  	xfs_daddr_t		*head_blk,
  	xfs_daddr_t		*tail_blk,
  	struct xlog_rec_header	*rhead,
  	xfs_daddr_t		rhead_blk,

  	char			*buffer,

  	bool			*clean)
  {
  	struct xlog_op_header	*op_head;
  	xfs_daddr_t		umount_data_blk;
  	xfs_daddr_t		after_umount_blk;
  	int			hblks;
  	int			error;
  	char			*offset;
  
  	*clean = false;
  
  	/*
  	 * 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.
  	 */

  	hblks = xlog_logrec_hblks(log, rhead);

  	after_umount_blk = xlog_wrap_logbno(log,
  			rhead_blk + hblks + BTOBB(be32_to_cpu(rhead->h_len)));

  	if (*head_blk == after_umount_blk &&
  	    be32_to_cpu(rhead->h_num_logops) == 1) {

  		umount_data_blk = xlog_wrap_logbno(log, rhead_blk + hblks);

  		error = xlog_bread(log, umount_data_blk, 1, buffer, &offset);

  		if (error)
  			return error;
  
  		op_head = (struct xlog_op_header *)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;
  
  			*clean = true;
  		}
  	}
  
  	return 0;
  }

  static void
  xlog_set_state(
  	struct xlog		*log,
  	xfs_daddr_t		head_blk,
  	struct xlog_rec_header	*rhead,
  	xfs_daddr_t		rhead_blk,
  	bool			bump_cycle)
  {
  	/*
  	 * 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 = rhead_blk;
  	log->l_curr_block = (int)head_blk;
  	log->l_curr_cycle = be32_to_cpu(rhead->h_cycle);
  	if (bump_cycle)
  		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));
  }

  /*

   * 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(

  	struct xlog		*log,

  	xfs_daddr_t		*head_blk,

  	xfs_daddr_t		*tail_blk)

  {
  	xlog_rec_header_t	*rhead;

  	char			*offset = NULL;

  	char			*buffer;

  	int			error;

  	xfs_daddr_t		rhead_blk;

  	xfs_lsn_t		tail_lsn;

  	bool			wrapped = false;

  	bool			clean = false;

  
  	/*
  	 * Find previous log record
  	 */
  	if ((error = xlog_find_head(log, head_blk)))
  		return error;

  	ASSERT(*head_blk < INT_MAX);

  	buffer = xlog_alloc_buffer(log, 1);
  	if (!buffer)

  		return -ENOMEM;

  	if (*head_blk == 0) {				/* special case */

  		error = xlog_bread(log, 0, 1, buffer, &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 through the log looking for the log record header
  	 * block. This wraps all the way back around to the head so something is
  	 * seriously wrong if we can't find it.

  	 */

  	error = xlog_rseek_logrec_hdr(log, *head_blk, *head_blk, 1, buffer,

  				      &rhead_blk, &rhead, &wrapped);
  	if (error < 0)

  		goto done;

  	if (!error) {
  		xfs_warn(log->l_mp, "%s: couldn't find sync record", __func__);

  		error = -EFSCORRUPTED;
  		goto done;

  	}
  	*tail_blk = BLOCK_LSN(be64_to_cpu(rhead->h_tail_lsn));

  
  	/*

  	 * Set the log state based on the current head record.

  	 */

  	xlog_set_state(log, *head_blk, rhead, rhead_blk, wrapped);

  	tail_lsn = atomic64_read(&log->l_tail_lsn);

  
  	/*

  	 * Look for an unmount record at the head of the log. This sets the log
  	 * state to determine whether recovery is necessary.

  	 */

  	error = xlog_check_unmount_rec(log, head_blk, tail_blk, rhead,

  				       rhead_blk, buffer, &clean);

  	if (error)
  		goto done;

  
  	/*

  	 * Verify the log head if the log is not clean (e.g., we have anything
  	 * but an unmount record at the head). This uses CRC verification to
  	 * detect and trim torn writes. If discovered, CRC failures are
  	 * considered torn writes and the log head is trimmed accordingly.

  	 *

  	 * Note that we can only run CRC verification when the log is dirty
  	 * because there's no guarantee that the log data behind an unmount
  	 * record is compatible with the current architecture.

  	 */

  	if (!clean) {
  		xfs_daddr_t	orig_head = *head_blk;

  		error = xlog_verify_head(log, head_blk, tail_blk, buffer,

  					 &rhead_blk, &rhead, &wrapped);

  		if (error)

  			goto done;

  		/* update in-core state again if the head changed */
  		if (*head_blk != orig_head) {
  			xlog_set_state(log, *head_blk, rhead, rhead_blk,
  				       wrapped);
  			tail_lsn = atomic64_read(&log->l_tail_lsn);
  			error = xlog_check_unmount_rec(log, head_blk, tail_blk,

  						       rhead, rhead_blk, buffer,

  						       &clean);
  			if (error)
  				goto done;

  		}
  	}
  
  	/*

  	 * 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.
  	 */
  	if (clean)
  		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_targ))

  		error = xlog_clear_stale_blocks(log, tail_lsn);

  done:

  	kmem_free(buffer);

  
  	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(

  	struct xlog	*log,

  	xfs_daddr_t	*blk_no)
  {

  	char		*buffer;

  	char		*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 */

  	buffer = xlog_alloc_buffer(log, 1);
  	if (!buffer)

  		return -ENOMEM;

  	error = xlog_bread(log, 0, 1, buffer, &offset);

  	if (error)

  		goto out_free_buffer;

  	first_cycle = xlog_get_cycle(offset);

  	if (first_cycle == 0) {		/* completely zeroed log */
  		*blk_no = 0;

  		kmem_free(buffer);

  		return 1;

  	}
  
  	/* check partially zeroed log */

  	error = xlog_bread(log, log_bbnum-1, 1, buffer, &offset);

  	if (error)

  		goto out_free_buffer;

  	last_cycle = xlog_get_cycle(offset);

  	if (last_cycle != 0) {		/* log completely written to */

  		kmem_free(buffer);

  		return 0;

  	}
  
  	/* we have a partially zeroed log */
  	last_blk = log_bbnum-1;

  	error = xlog_find_cycle_start(log, buffer, 0, &last_blk, 0);
  	if (error)
  		goto out_free_buffer;

  
  	/*
  	 * 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 out_free_buffer;

  	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.
  	 */

  	error = xlog_find_verify_log_record(log, start_blk, &last_blk, 0);
  	if (error == 1)
  		error = -EIO;
  	if (error)

  		goto out_free_buffer;

  
  	*blk_no = last_blk;

  out_free_buffer:
  	kmem_free(buffer);

  	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(

  	struct xlog		*log,

  	char			*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(

  	struct xlog	*log,

  	int		cycle,
  	int		start_block,
  	int		blocks,
  	int		tail_cycle,
  	int		tail_block)
  {

  	char		*offset;

  	char		*buffer;

  	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 (bufblks > log->l_logBBsize)
  		bufblks >>= 1;

  	while (!(buffer = xlog_alloc_buffer(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, buffer);

  		if (error)

  			goto out_free_buffer;

  		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)) {

  			error = xlog_bread_noalign(log, ealign, sectbb,

  					buffer + BBTOB(ealign - start_block));

  			if (error)
  				break;

  		}

  		offset = buffer + xlog_align(log, start_block);

  		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, buffer);

  		if (error)
  			break;
  		start_block += endcount;
  		j = 0;
  	}

  out_free_buffer:
  	kmem_free(buffer);

  	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(

  	struct xlog	*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 (XFS_IS_CORRUPT(log->l_mp,
  				   head_block < tail_block ||
  				   head_block >= log->l_logBBsize))

  			return -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 (XFS_IS_CORRUPT(log->l_mp,
  				   head_block >= tail_block ||
  				   head_cycle != tail_cycle + 1))

  			return -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;
  }

  /*
   * Release the recovered intent item in the AIL that matches the given intent
   * type and intent id.
   */
  void
  xlog_recover_release_intent(
  	struct xlog		*log,
  	unsigned short		intent_type,
  	uint64_t		intent_id)
  {
  	struct xfs_ail_cursor	cur;
  	struct xfs_log_item	*lip;
  	struct xfs_ail		*ailp = log->l_ailp;
  
  	spin_lock(&ailp->ail_lock);
  	for (lip = xfs_trans_ail_cursor_first(ailp, &cur, 0); lip != NULL;
  	     lip = xfs_trans_ail_cursor_next(ailp, &cur)) {
  		if (lip->li_type != intent_type)
  			continue;
  		if (!lip->li_ops->iop_match(lip, intent_id))
  			continue;
  
  		spin_unlock(&ailp->ail_lock);
  		lip->li_ops->iop_release(lip);
  		spin_lock(&ailp->ail_lock);
  		break;
  	}
  
  	xfs_trans_ail_cursor_done(&cur);
  	spin_unlock(&ailp->ail_lock);
  }

  /******************************************************************************
   *
   *		Log recover routines
   *
   ******************************************************************************
   */

  static const struct xlog_recover_item_ops *xlog_recover_item_ops[] = {
  	&xlog_buf_item_ops,
  	&xlog_inode_item_ops,
  	&xlog_dquot_item_ops,
  	&xlog_quotaoff_item_ops,
  	&xlog_icreate_item_ops,
  	&xlog_efi_item_ops,
  	&xlog_efd_item_ops,
  	&xlog_rui_item_ops,
  	&xlog_rud_item_ops,
  	&xlog_cui_item_ops,
  	&xlog_cud_item_ops,
  	&xlog_bui_item_ops,
  	&xlog_bud_item_ops,
  };
  
  static const struct xlog_recover_item_ops *
  xlog_find_item_ops(
  	struct xlog_recover_item		*item)
  {
  	unsigned int				i;
  
  	for (i = 0; i < ARRAY_SIZE(xlog_recover_item_ops); i++)
  		if (ITEM_TYPE(item) == xlog_recover_item_ops[i]->item_type)
  			return xlog_recover_item_ops[i];
  
  	return NULL;
  }

  /*

   * Sort the log items in the transaction.
   *
   * The ordering constraints are defined by the inode allocation and unlink
   * behaviour. The rules are:
   *
   *	1. Every item is only logged once in a given transaction. Hence it
   *	   represents the last logged state of the item. Hence ordering is
   *	   dependent on the order in which operations need to be performed so
   *	   required initial conditions are always met.
   *
   *	2. Cancelled buffers are recorded in pass 1 in a separate table and
   *	   there's nothing to replay from them so we can simply cull them
   *	   from the transaction. However, we can't do that until after we've
   *	   replayed all the other items because they may be dependent on the
   *	   cancelled buffer and replaying the cancelled buffer can remove it
   *	   form the cancelled buffer table. Hence they have tobe done last.
   *
   *	3. Inode allocation buffers must be replayed before inode items that

   *	   read the buffer and replay changes into it. For filesystems using the
   *	   ICREATE transactions, this means XFS_LI_ICREATE objects need to get
   *	   treated the same as inode allocation buffers as they create and
   *	   initialise the buffers directly.

   *
   *	4. Inode unlink buffers must be replayed after inode items are replayed.
   *	   This ensures that inodes are completely flushed to the inode buffer
   *	   in a "free" state before we remove the unlinked inode list pointer.
   *
   * Hence the ordering needs to be inode allocation buffers first, inode items
   * second, inode unlink buffers third and cancelled buffers last.
   *
   * But there's a problem with that - we can't tell an inode allocation buffer
   * apart from a regular buffer, so we can't separate them. We can, however,
   * tell an inode unlink buffer from the others, and so we can separate them out
   * from all the other buffers and move them to last.
   *
   * Hence, 4 lists, in order from head to tail:

   *	- buffer_list for all buffers except cancelled/inode unlink buffers
   *	- item_list for all non-buffer items
   *	- inode_buffer_list for inode unlink buffers
   *	- cancel_list for the cancelled buffers
   *
   * Note that we add objects to the tail of the lists so that first-to-last
   * ordering is preserved within the lists. Adding objects to the head of the
   * list means when we traverse from the head we walk them in last-to-first
   * order. For cancelled buffers and inode unlink buffers this doesn't matter,
   * but for all other items there may be specific ordering that we need to
   * preserve.

   */

  STATIC int
  xlog_recover_reorder_trans(

  	struct xlog		*log,
  	struct xlog_recover	*trans,

  	int			pass)

  {

  	struct xlog_recover_item *item, *n;

  	int			error = 0;

  	LIST_HEAD(sort_list);

  	LIST_HEAD(cancel_list);
  	LIST_HEAD(buffer_list);
  	LIST_HEAD(inode_buffer_list);

  	LIST_HEAD(item_list);

  
  	list_splice_init(&trans->r_itemq, &sort_list);
  	list_for_each_entry_safe(item, n, &sort_list, ri_list) {

  		enum xlog_recover_reorder	fate = XLOG_REORDER_ITEM_LIST;

  		item->ri_ops = xlog_find_item_ops(item);
  		if (!item->ri_ops) {

  			xfs_warn(log->l_mp,

  				"%s: unrecognized type of log operation (%d)",
  				__func__, ITEM_TYPE(item));

  			ASSERT(0);

  			/*
  			 * return the remaining items back to the transaction
  			 * item list so they can be freed in caller.
  			 */
  			if (!list_empty(&sort_list))
  				list_splice_init(&sort_list, &trans->r_itemq);

  			error = -EFSCORRUPTED;
  			break;
  		}
  
  		if (item->ri_ops->reorder)
  			fate = item->ri_ops->reorder(item);
  
  		switch (fate) {
  		case XLOG_REORDER_BUFFER_LIST:
  			list_move_tail(&item->ri_list, &buffer_list);
  			break;
  		case XLOG_REORDER_CANCEL_LIST:
  			trace_xfs_log_recover_item_reorder_head(log,
  					trans, item, pass);
  			list_move(&item->ri_list, &cancel_list);
  			break;
  		case XLOG_REORDER_INODE_BUFFER_LIST:
  			list_move(&item->ri_list, &inode_buffer_list);
  			break;
  		case XLOG_REORDER_ITEM_LIST:
  			trace_xfs_log_recover_item_reorder_tail(log,
  							trans, item, pass);
  			list_move_tail(&item->ri_list, &item_list);
  			break;

  		}

  	}

  	ASSERT(list_empty(&sort_list));

  	if (!list_empty(&buffer_list))
  		list_splice(&buffer_list, &trans->r_itemq);

  	if (!list_empty(&item_list))
  		list_splice_tail(&item_list, &trans->r_itemq);

  	if (!list_empty(&inode_buffer_list))
  		list_splice_tail(&inode_buffer_list, &trans->r_itemq);
  	if (!list_empty(&cancel_list))
  		list_splice_tail(&cancel_list, &trans->r_itemq);

  	return error;

  }

  void

  xlog_buf_readahead(
  	struct xlog		*log,
  	xfs_daddr_t		blkno,
  	uint			len,
  	const struct xfs_buf_ops *ops)
  {
  	if (!xlog_is_buffer_cancelled(log, blkno, len))
  		xfs_buf_readahead(log->l_mp->m_ddev_targp, blkno, len, ops);
  }

  STATIC int

  xlog_recover_items_pass2(
  	struct xlog                     *log,
  	struct xlog_recover             *trans,
  	struct list_head                *buffer_list,
  	struct list_head                *item_list)
  {
  	struct xlog_recover_item	*item;
  	int				error = 0;
  
  	list_for_each_entry(item, item_list, ri_list) {

  		trace_xfs_log_recover_item_recover(log, trans, item,
  				XLOG_RECOVER_PASS2);
  
  		if (item->ri_ops->commit_pass2)
  			error = item->ri_ops->commit_pass2(log, buffer_list,
  					item, trans->r_lsn);

  		if (error)
  			return error;
  	}
  
  	return error;
  }

  /*
   * 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 xlog		*log,

  	struct xlog_recover	*trans,

  	int			pass,
  	struct list_head	*buffer_list)

  {

  	int				error = 0;

  	int				items_queued = 0;
  	struct xlog_recover_item	*item;
  	struct xlog_recover_item	*next;

  	LIST_HEAD			(ra_list);
  	LIST_HEAD			(done_list);
  
  	#define XLOG_RECOVER_COMMIT_QUEUE_MAX 100

  	hlist_del_init(&trans->r_list);

  
  	error = xlog_recover_reorder_trans(log, trans, pass);
  	if (error)

  		return error;

  	list_for_each_entry_safe(item, next, &trans->r_itemq, ri_list) {

  		trace_xfs_log_recover_item_recover(log, trans, item, pass);

  		switch (pass) {
  		case XLOG_RECOVER_PASS1:

  			if (item->ri_ops->commit_pass1)
  				error = item->ri_ops->commit_pass1(log, item);

  			break;
  		case XLOG_RECOVER_PASS2:

  			if (item->ri_ops->ra_pass2)
  				item->ri_ops->ra_pass2(log, item);

  			list_move_tail(&item->ri_list, &ra_list);
  			items_queued++;
  			if (items_queued >= XLOG_RECOVER_COMMIT_QUEUE_MAX) {
  				error = xlog_recover_items_pass2(log, trans,

  						buffer_list, &ra_list);

  				list_splice_tail_init(&ra_list, &done_list);
  				items_queued = 0;
  			}

  			break;
  		default:
  			ASSERT(0);
  		}

  		if (error)

  			goto out;

  	}

  out:
  	if (!list_empty(&ra_list)) {
  		if (!error)
  			error = xlog_recover_items_pass2(log, trans,

  					buffer_list, &ra_list);

  		list_splice_tail_init(&ra_list, &done_list);
  	}
  
  	if (!list_empty(&done_list))
  		list_splice_init(&done_list, &trans->r_itemq);

  	return error;

  }

  STATIC void
  xlog_recover_add_item(
  	struct list_head	*head)
  {

  	struct xlog_recover_item *item;

  	item = kmem_zalloc(sizeof(struct xlog_recover_item), 0);

  	INIT_LIST_HEAD(&item->ri_list);
  	list_add_tail(&item->ri_list, head);
  }

  STATIC int

  xlog_recover_add_to_cont_trans(
  	struct xlog		*log,
  	struct xlog_recover	*trans,

  	char			*dp,

  	int			len)

  {

  	struct xlog_recover_item *item;

  	char			*ptr, *old_ptr;

  	int			old_len;

  	/*
  	 * If the transaction is empty, the header was split across this and the
  	 * previous record. Copy the rest of the header.
  	 */

  	if (list_empty(&trans->r_itemq)) {

  		ASSERT(len <= sizeof(struct xfs_trans_header));

  		if (len > sizeof(struct xfs_trans_header)) {
  			xfs_warn(log->l_mp, "%s: bad header length", __func__);

  			return -EFSCORRUPTED;

  		}

  		xlog_recover_add_item(&trans->r_itemq);

  		ptr = (char *)&trans->r_theader +

  				sizeof(struct xfs_trans_header) - len;

  		memcpy(ptr, dp, len);
  		return 0;
  	}

  	/* take the tail entry */

  	item = list_entry(trans->r_itemq.prev, struct xlog_recover_item,
  			  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 = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);

  	memcpy(&ptr[old_len], dp, len);
  	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 xlog		*log,
  	struct xlog_recover	*trans,

  	char			*dp,

  	int			len)
  {

  	struct xfs_inode_log_format	*in_f;			/* any will do */

  	struct xlog_recover_item *item;

  	char			*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 -EFSCORRUPTED;

  		}

  
  		if (len > sizeof(struct xfs_trans_header)) {
  			xfs_warn(log->l_mp, "%s: bad header length", __func__);
  			ASSERT(0);

  			return -EFSCORRUPTED;

  		}
  
  		/*
  		 * The transaction header can be arbitrarily split across op
  		 * records. If we don't have the whole thing here, copy what we
  		 * do have and handle the rest in the next record.
  		 */
  		if (len == sizeof(struct xfs_trans_header))

  			xlog_recover_add_item(&trans->r_itemq);
  		memcpy(&trans->r_theader, dp, len);
  		return 0;
  	}

  	ptr = kmem_alloc(len, 0);

  	memcpy(ptr, dp, len);

  	in_f = (struct xfs_inode_log_format *)ptr;

  
  	/* take the tail entry */

  	item = list_entry(trans->r_itemq.prev, struct xlog_recover_item,
  			  ri_list);