Fix libxfs device flush ioctl, sync with kernel source.

[thirdparty/xfsprogs-dev.git] / libxlog / xfs_log_recover.c

/*
 * Copyright (c) 2000-2002 Silicon Graphics, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 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.
 *
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.  Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 *
 * http://www.sgi.com
 *
 * For further information regarding this notice, see:
 *
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

#include <libxlog.h>

/*
 * 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.
 */
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_daddr_t mid_blk;
        uint    mid_cycle;
        int     error;

        mid_blk = BLK_AVG(first_blk, *last_blk);
        while (mid_blk != first_blk && mid_blk != *last_blk) {
                if ((error = xlog_bread(log, mid_blk, 1, bp)))
                        return error;
                mid_cycle = GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT);
                if (mid_cycle == cycle) {
                        *last_blk = mid_blk;
                        /* last_half_cycle == mid_cycle */
                } else {
                        first_blk = mid_blk;
                        /* first_half_cycle == mid_cycle */
                }
                mid_blk = BLK_AVG(first_blk, *last_blk);
        }
        ASSERT((mid_blk == first_blk && mid_blk+1 == *last_blk) ||
               (mid_blk == *last_blk && mid_blk-1 == first_blk));

        return 0;
}       /* xlog_find_cycle_start */


/*
 * Check that the range of blocks does not contain the cycle number
 * given.  The scan needs to occur from front to back and the ptr into the
 * region must be updated since a later routine will need to perform another
 * test.  If the region is completely good, we end up returning the same
 * last block number.
 *
 * Set blkno to -1 if we encounter no errors.  This is an invalid block number
 * since we don't ever expect logs to get this large.
 */

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;
        char                    *buf        = NULL;
        int                     error       = 0;
        xfs_daddr_t             bufblks;

        bufblks = 1 << ffs(nbblks);

        while (!(bp = xlog_get_bp(bufblks, log->l_mp))) {
                /* can't get enough memory to do everything in one big buffer */
                bufblks >>= 1;
                if (!bufblks)
                        return ENOMEM;
        }


        for (i = start_blk; i < start_blk + nbblks; i += bufblks)  {
                int bcount = min(bufblks, (start_blk + nbblks - i));

                if ((error = xlog_bread(log, i, bcount, bp)))
                        goto out;

                buf = XFS_BUF_PTR(bp);
                for (j = 0; j < bcount; j++) {
                        cycle = GET_CYCLE(buf, ARCH_CONVERT);
                        if (cycle == stop_on_cycle_no) {
                                *new_blk = i+j;
                                goto out;
                        }

                        buf += BBSIZE;
                }
        }

        *new_blk = -1;

out:
        xlog_put_bp(bp);

        return error;
}       /* xlog_find_verify_cycle */


/*
 * 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;
    char                *buf        = 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(num_blks, log->l_mp))) {
        if (!(bp = xlog_get_bp(1, log->l_mp)))
            return ENOMEM;
        smallmem = 1;
        buf = XFS_BUF_PTR(bp);
    } else {
        if ((error = xlog_bread(log, start_blk, num_blks, bp)))
            goto out;
        buf = XFS_BUF_PTR(bp) + (num_blks - 1) * BBSIZE;
    }


    for (i=(*last_blk)-1; i>=0; i--) {
        if (i < start_blk) {
            /* legal log record not found */
            xlog_warn("XFS: Log inconsistent (didn't find previous header)");
            ASSERT(0);
            error = XFS_ERROR(EIO);
            goto out;
        }

        if (smallmem && (error = xlog_bread(log, i, 1, bp)))
            goto out;
        head = (xlog_rec_header_t*)buf;

        if (INT_GET(head->h_magicno, ARCH_CONVERT) == XLOG_HEADER_MAGIC_NUM)
            break;

        if (!smallmem)
            buf -= 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)) {
        int h_size = INT_GET(head->h_size, ARCH_CONVERT);
        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(INT_GET(head->h_len, ARCH_CONVERT))+xhdrs)
            *last_blk = i;

out:
    xlog_put_bp(bp);

    return error;
}       /* xlog_find_verify_log_record */

/*
 * 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.
 *
 * Also called from xfs_log_print.c
 *
 * Return: zero if normal, non-zero if error.
 */
int
xlog_find_head(xlog_t  *log,
               xfs_daddr_t *return_head_blk)
{
    xfs_buf_t   *bp;
    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
             */
            xlog_warn("XFS: totally zeroed log\n");
        }

        return 0;
    } else if (error) {
        xlog_warn("XFS: empty log check failed");
        return error;
    }

    first_blk = 0;                              /* get cycle # of 1st block */
    bp = xlog_get_bp(1,log->l_mp);
    if (!bp)
        return ENOMEM;
    if ((error = xlog_bread(log, 0, 1, bp)))
        goto bp_err;
    first_half_cycle = GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT);

    last_blk = head_blk = log_bbnum-1;          /* get cycle # of last block */
    if ((error = xlog_bread(log, last_blk, 1, bp)))
        goto bp_err;
    last_half_cycle = GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT);
    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 illegal 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 somwhere 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 ...
         * 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
         *        x + 1 ... | x | x + 1 | x ...
         *                               ^ binary search stopped here
         * or
         *        x + 1 ... | x ... | x - 1 | x
         *        <---------> less than scan distance
         */
        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.
         */
        start_blk = log_bbnum - num_scan_bblks + head_blk;
        ASSERT(head_blk <= INT_MAX && (xfs_daddr_t) num_scan_bblks-head_blk >= 0);
        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 bad_blk;
        }

        /*
         * 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;
    }

bad_blk:
    /*
     * Now we need to make sure head_blk is not pointing to a block in
     * the middle of a log record.
     */
    num_scan_bblks = BTOBB(XLOG_MAX_RECORD_BSIZE);
    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)
            xlog_warn("XFS: failed to find log head");

        return error;
}       /* xlog_find_head */

/*
 * 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.
 */
int
xlog_find_tail(xlog_t  *log,
               xfs_daddr_t *head_blk,
               xfs_daddr_t *tail_blk,
               int readonly)
{
        xlog_rec_header_t       *rhead;
        xlog_op_header_t        *op_head;
        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(1,log->l_mp);
        if (!bp)
                return ENOMEM;
        if (*head_blk == 0) {                           /* special case */
                if ((error = xlog_bread(log, 0, 1, bp)))
                        goto bread_err;
                if (GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT) == 0) {
                        *tail_blk = 0;
                        /* leave all other log inited values alone */
                        goto exit;
                }
        }

        /*
         * Search backwards looking for log record header block
         */
        ASSERT(*head_blk < INT_MAX);
        for (i = (int)(*head_blk) - 1; i >= 0; i--) {
                if ((error = xlog_bread(log, i, 1, bp)))
                        goto bread_err;
                if (XLOG_HEADER_MAGIC_NUM ==
                    INT_GET(*(uint *)(XFS_BUF_PTR(bp)), ARCH_CONVERT)) {
                        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--) {
                        if ((error = xlog_bread(log, i, 1, bp)))
                                goto bread_err;
                        if (XLOG_HEADER_MAGIC_NUM ==
                            INT_GET(*(uint*)(XFS_BUF_PTR(bp)), ARCH_CONVERT)) {
                                found = 2;
                                break;
                        }
                }
        }
        if (!found) {
                xlog_warn("XFS: xlog_find_tail: couldn't find sync record");
                ASSERT(0);
                return XFS_ERROR(EIO);
        }

        /* find blk_no of tail of log */
        rhead = (xlog_rec_header_t *)XFS_BUF_PTR(bp);
        *tail_blk = BLOCK_LSN(rhead->h_tail_lsn, ARCH_CONVERT);

        /*
         * 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 = INT_GET(rhead->h_cycle, ARCH_CONVERT);
        if (found == 2)
                log->l_curr_cycle++;
        log->l_tail_lsn = INT_GET(rhead->h_tail_lsn, ARCH_CONVERT);
        log->l_last_sync_lsn = INT_GET(rhead->h_lsn, ARCH_CONVERT);
        log->l_grant_reserve_cycle = log->l_curr_cycle;
        log->l_grant_reserve_bytes = BBTOB(log->l_curr_block);
        log->l_grant_write_cycle = log->l_curr_cycle;
        log->l_grant_write_bytes = 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 = INT_GET(rhead->h_size, ARCH_CONVERT);
                int     h_version = INT_GET(rhead->h_version, ARCH_CONVERT);

                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(INT_GET(rhead->h_len, ARCH_CONVERT))) % log->l_logBBsize;
        tail_lsn = log->l_tail_lsn;
        if (*head_blk == after_umount_blk &&
            INT_GET(rhead->h_num_logops, ARCH_CONVERT) == 1) {
                umount_data_blk = (i + hblks) % log->l_logBBsize;
                if ((error = xlog_bread(log, umount_data_blk, 1, bp))) {
                        goto bread_err;
                }
                op_head = (xlog_op_header_t *)XFS_BUF_PTR(bp);
                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.
                         */
                        ASSIGN_ANY_LSN(log->l_tail_lsn, log->l_curr_cycle,
                                        after_umount_blk, ARCH_NOCONVERT);
                        ASSIGN_ANY_LSN(log->l_last_sync_lsn, log->l_curr_cycle,
                                        after_umount_blk, ARCH_NOCONVERT);
                        *tail_blk = after_umount_blk;
                }
        }

#ifdef __KERNEL__
        /*
         * 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 (!is_read_only(log->l_mp->m_logdev_targp->pbr_kdev)) {
                error = xlog_clear_stale_blocks(log, tail_lsn);
        }
#endif

bread_err:
exit:
        xlog_put_bp(bp);

        if (error)
                xlog_warn("XFS: failed to locate log tail");

        return error;
}       /* xlog_find_tail */

/*
 * 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
 */
int
xlog_find_zeroed(struct log     *log,
                 xfs_daddr_t    *blk_no)
{
        xfs_buf_t       *bp;
        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;

        error = 0;
        /* check totally zeroed log */
        bp = xlog_get_bp(1,log->l_mp);
        if (!bp)
                return ENOMEM;
        if ((error = xlog_bread(log, 0, 1, bp)))
                goto bp_err;
        first_cycle = GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT);
        if (first_cycle == 0) {         /* completely zeroed log */
                *blk_no = 0;
                xlog_put_bp(bp);
                return -1;
        }

        /* check partially zeroed log */
        if ((error = xlog_bread(log, log_bbnum-1, 1, bp)))
                goto bp_err;
        last_cycle = GET_CYCLE(XFS_BUF_PTR(bp), ARCH_CONVERT);
        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.
                 */
                xlog_warn("XFS: 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;
}       /* xlog_find_zeroed */

/* stuff for transactional view */
STATIC void
xlog_unpack_data(xlog_rec_header_t *rhead,
                 xfs_caddr_t       dp,
                 xlog_t            *log)
{
        int i, j, k;
        union ich {
                xlog_rec_header_t       hic_header;
                xlog_rec_ext_header_t   hic_xheader;
                char                    hic_sector[XLOG_HEADER_SIZE];
        } *xhdr;

#if defined(DEBUG) && defined(XFS_LOUD_RECOVERY)
        uint *up = (uint *)dp;
        uint chksum = 0;
#endif

        for (i=0; i < BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT)) &&
                  i < (XLOG_HEADER_CYCLE_SIZE / BBSIZE); i++) {
                *(uint *)dp = *(uint *)&rhead->h_cycle_data[i];
                dp += BBSIZE;
        }

        if (XFS_SB_VERSION_HASLOGV2(&log->l_mp->m_sb)) {
                xhdr = (union ich*)rhead;
                for ( ; i < BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT)); i++) {
                        j = i / (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        k = i % (XLOG_HEADER_CYCLE_SIZE / BBSIZE);
                        *(uint *)dp = xhdr[j].hic_xheader.xh_cycle_data[k];
                        dp += BBSIZE;
                }
        }

#if defined(DEBUG) && defined(XFS_LOUD_RECOVERY)
        /* divide length by 4 to get # words */
        for (i=0; i < INT_GET(rhead->h_len, ARCH_CONVERT) >> 2; i++) {
                chksum ^= INT_GET(*up, ARCH_CONVERT);
                up++;
        }
        if (chksum != INT_GET(rhead->h_chksum, ARCH_CONVERT)) {
            if (!INT_ISZERO(rhead->h_chksum, ARCH_CONVERT) ||
                ((log->l_flags & XLOG_CHKSUM_MISMATCH) == 0)) {
                    cmn_err(CE_DEBUG,
                        "XFS: LogR chksum mismatch: was (0x%x) is (0x%x)",
                            INT_GET(rhead->h_chksum, ARCH_CONVERT), chksum);
                    cmn_err(CE_DEBUG,
"XFS: Disregard message if filesystem was created with non-DEBUG kernel");
                    if (XFS_SB_VERSION_HASLOGV2(&log->l_mp->m_sb)) {
                            cmn_err(CE_DEBUG,
                                "XFS: LogR this is a LogV2 filesystem\n");
                    }
                    log->l_flags |= XLOG_CHKSUM_MISMATCH;
            }
        }
#endif /* DEBUG && XFS_LOUD_RECOVERY */
}       /* xlog_unpack_data */

STATIC xlog_recover_t *
xlog_recover_find_tid(xlog_recover_t *q,
                      xlog_tid_t     tid)
{
        xlog_recover_t *p = q;

        while (p != NULL) {
                if (p->r_log_tid == tid)
                    break;
                p = p->r_next;
        }
        return p;
}       /* xlog_recover_find_tid */

STATIC void
xlog_recover_put_hashq(xlog_recover_t **q,
                       xlog_recover_t *trans)
{
        trans->r_next = *q;
        *q = trans;
}       /* xlog_recover_put_hashq */

STATIC void
xlog_recover_new_tid(xlog_recover_t     **q,
                     xlog_tid_t         tid,
                     xfs_lsn_t          lsn)
{
        xlog_recover_t  *trans;

        trans = kmem_zalloc(sizeof(xlog_recover_t), 0);
        trans->r_log_tid   = tid;
        trans->r_lsn       = lsn;
        xlog_recover_put_hashq(q, trans);
}       /* xlog_recover_new_tid */


STATIC int
xlog_recover_unlink_tid(xlog_recover_t  **q,
                        xlog_recover_t  *trans)
{
        xlog_recover_t  *tp;
        int             found = 0;

        ASSERT(trans != 0);
        if (trans == *q) {
                *q = (*q)->r_next;
        } else {
                tp = *q;
                while (tp != 0) {
                        if (tp->r_next == trans) {
                                found = 1;
                                break;
                        }
                        tp = tp->r_next;
                }
                if (!found) {
                        xlog_warn(
                             "XFS: xlog_recover_unlink_tid: trans not found");
                        ASSERT(0);
                        return XFS_ERROR(EIO);
                }
                tp->r_next = tp->r_next->r_next;
        }
        return 0;
}       /* xlog_recover_unlink_tid */

/*
 * Free up any resources allocated by the transaction
 *
 * Remember that EFIs, EFDs, and IUNLINKs are handled later.
 */
STATIC void
xlog_recover_free_trans(xlog_recover_t      *trans)
{
        xlog_recover_item_t *first_item, *item, *free_item;
        int i;

        item = first_item = trans->r_itemq;
        do {
                free_item = item;
                item = item->ri_next;
                 /* Free the regions in the item. */
                for (i = 0; i < free_item->ri_cnt; i++) {
                        kmem_free(free_item->ri_buf[i].i_addr,
                                  free_item->ri_buf[i].i_len);
                }
                /* Free the item itself */
                kmem_free(free_item->ri_buf,
                          (free_item->ri_total * sizeof(xfs_log_iovec_t)));
                kmem_free(free_item, sizeof(xlog_recover_item_t));
        } while (first_item != item);
        /* Free the transaction recover structure */
        kmem_free(trans, sizeof(xlog_recover_t));
}       /* xlog_recover_free_trans */


STATIC int
xlog_recover_commit_trans(xlog_t         *log,
                          xlog_recover_t **q,
                          xlog_recover_t *trans,
                          int            pass)
{
        int error;

        if ((error = xlog_recover_unlink_tid(q, trans)))
                return error;
        if ((error = xlog_recover_do_trans(log, trans, pass)))
                return error;
        xlog_recover_free_trans(trans);                 /* no error */
        return 0;
}       /* xlog_recover_commit_trans */

STATIC void
xlog_recover_insert_item_backq(xlog_recover_item_t **q,
                               xlog_recover_item_t *item)
{
        if (*q == 0) {
                item->ri_prev = item->ri_next = item;
                *q = item;
        } else {
                item->ri_next           = *q;
                item->ri_prev           = (*q)->ri_prev;
                (*q)->ri_prev           = item;
                item->ri_prev->ri_next  = item;
        }
}       /* xlog_recover_insert_item_backq */

STATIC void
xlog_recover_add_item(xlog_recover_item_t **itemq)
{
        xlog_recover_item_t *item;

        item = kmem_zalloc(sizeof(xlog_recover_item_t), 0);
        xlog_recover_insert_item_backq(itemq, item);
}       /* xlog_recover_add_item */

/* 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(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;
        ptr = kmem_zalloc(len, 0);
        memcpy(ptr, dp, len);

        in_f = (xfs_inode_log_format_t *)ptr;
        item = trans->r_itemq;
        if (item == 0) {
                ASSERT(*(uint *)dp == XFS_TRANS_HEADER_MAGIC);
                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;
        }
        if (item->ri_prev->ri_total != 0 &&
             item->ri_prev->ri_total == item->ri_prev->ri_cnt) {
                xlog_recover_add_item(&trans->r_itemq);
        }
        item = trans->r_itemq;
        item = item->ri_prev;

        if (item->ri_total == 0) {              /* first region to be added */
                item->ri_total  = in_f->ilf_size;
                ASSERT(item->ri_total <= XLOG_MAX_REGIONS_IN_ITEM);
                item->ri_buf = kmem_zalloc((item->ri_total *
                                            sizeof(xfs_log_iovec_t)), 0);
        }
        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++;
        return 0;
}       /* xlog_recover_add_to_trans */

STATIC int
xlog_recover_add_to_cont_trans(xlog_recover_t   *trans,
                               xfs_caddr_t              dp,
                               int              len)
{
        xlog_recover_item_t     *item;
        xfs_caddr_t                     ptr, old_ptr;
        int                     old_len;

        item = trans->r_itemq;
        if (item == 0) {
                /* 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;
        }
        item = item->ri_prev;

        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, 0);
        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;
        return 0;
}       /* xlog_recover_add_to_cont_trans */

STATIC int
xlog_recover_unmount_trans(xlog_recover_t *trans)
{
        /* Do nothing now */
        xlog_warn("XFS: xlog_recover_unmount_trans: Unmount LR");
        return( 0 );
}       /* xlog_recover_unmount_trans */


STATIC int
xlog_recover_process_data(xlog_t            *log,
                          xlog_recover_t    *rhash[],
                          xlog_rec_header_t *rhead,
                          xfs_caddr_t       dp,
                          int               pass)
{
    xfs_caddr_t         lp         = dp+INT_GET(rhead->h_len, ARCH_CONVERT);
    int                 num_logops = INT_GET(rhead->h_num_logops, ARCH_CONVERT);
    xlog_op_header_t    *ohead;
    xlog_recover_t      *trans;
    xlog_tid_t          tid;
    int                 error;
    unsigned long       hash;
    uint                flags;

    /* 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) {
            xlog_warn("XFS: xlog_recover_process_data: bad clientid");
            ASSERT(0);
            return (XFS_ERROR(EIO));
        }
        tid = INT_GET(ohead->oh_tid, ARCH_CONVERT);
        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, INT_GET(rhead->h_lsn, ARCH_CONVERT));
        } else {
            ASSERT(dp+INT_GET(ohead->oh_len, ARCH_CONVERT) <= lp);
            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, &rhash[hash],
                                                      trans, pass);
                    break;
                }
                case XLOG_UNMOUNT_TRANS: {
                    error = xlog_recover_unmount_trans(trans);
                    break;
                }
                case XLOG_WAS_CONT_TRANS: {
                    error = xlog_recover_add_to_cont_trans(trans, dp,
                                  INT_GET(ohead->oh_len, ARCH_CONVERT));
                    break;
                }
                case XLOG_START_TRANS : {
                    xlog_warn("XFS: xlog_recover_process_data: bad transaction");
                    ASSERT(0);
                    error = XFS_ERROR(EIO);
                    break;
                }
                case 0:
                case XLOG_CONTINUE_TRANS: {
                    error = xlog_recover_add_to_trans(trans, dp,
                                   INT_GET(ohead->oh_len, ARCH_CONVERT));
                    break;
                }
                default: {
                    xlog_warn("XFS: xlog_recover_process_data: bad flag");
                    ASSERT(0);
                    error = XFS_ERROR(EIO);
                    break;
                }
            } /* switch */
            if (error)
                return error;
        } /* if */
        dp += INT_GET(ohead->oh_len, ARCH_CONVERT);
        num_logops--;
    }
    return( 0 );
}       /* xlog_recover_process_data */

/*
 * 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.
 */
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         bufaddr;
    xfs_buf_t           *hbp, *dbp;
    int                 error, h_size;
    int                 bblks, split_bblks;
    int                 hblks, split_hblks, wrapped_hblks;
    xlog_recover_t      *rhash[XLOG_RHASH_SIZE];

    error = 0;


    /*
     * 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(1, log->l_mp);
        if (!hbp)
            return ENOMEM;
        if ((error = xlog_bread(log, tail_blk, 1, hbp)))
            goto bread_err1;
        rhead = (xlog_rec_header_t *)XFS_BUF_PTR(hbp);
        ASSERT(INT_GET(rhead->h_magicno, ARCH_CONVERT) ==
                                                XLOG_HEADER_MAGIC_NUM);
        if ((INT_GET(rhead->h_version, ARCH_CONVERT) & (~XLOG_VERSION_OKBITS)) != 0) {
            xlog_warn("XFS: xlog_do_recovery_pass: unrecognised log version number.");
            error = XFS_ERROR(EIO);
            goto bread_err1;
        }
        h_size = INT_GET(rhead->h_size, ARCH_CONVERT);

        if ((INT_GET(rhead->h_version, ARCH_CONVERT) & 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(hblks, log->l_mp);
        } else {
            hblks=1;
        }
    } else {
        hblks=1;
        hbp = xlog_get_bp(1, log->l_mp);
        h_size = XLOG_BIG_RECORD_BSIZE;
    }

    if (!hbp)
        return ENOMEM;
    dbp = xlog_get_bp(BTOBB(h_size),log->l_mp);
    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; ) {
            if ((error = xlog_bread(log, blk_no, hblks, hbp)))
                goto bread_err2;
            rhead = (xlog_rec_header_t *)XFS_BUF_PTR(hbp);
            ASSERT(INT_GET(rhead->h_magicno, ARCH_CONVERT) == XLOG_HEADER_MAGIC_NUM);
            ASSERT(BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT) <= INT_MAX));
            bblks = (int) BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT));   /* blocks in data section */

            if ((INT_GET(rhead->h_magicno, ARCH_CONVERT) != XLOG_HEADER_MAGIC_NUM) ||
                (BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT) > INT_MAX)) ||
                (bblks <= 0) ||
                (blk_no > log->l_logBBsize)) {
                    error = EFSCORRUPTED;
                    goto bread_err2;
            }

            if ((INT_GET(rhead->h_version, ARCH_CONVERT) & (~XLOG_VERSION_OKBITS)) != 0) {
                xlog_warn("XFS: xlog_do_recovery_pass: unrecognised log version number.");
                error = XFS_ERROR(EIO);
                goto bread_err2;
            }
            bblks = (int) BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT));   /* blocks in data section */
            if (bblks > 0) {
                if ((error = xlog_bread(log, blk_no+hblks, bblks, dbp)))
                    goto bread_err2;
                xlog_unpack_data(rhead, XFS_BUF_PTR(dbp), log);
                if ((error = xlog_recover_process_data(log, rhash,
                                                      rhead, XFS_BUF_PTR(dbp),
                                                      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
             */
            wrapped_hblks = 0;
            if (blk_no+hblks <= log->l_logBBsize) {
                /* Read header in one read */
                if ((error = xlog_bread(log, blk_no, hblks, hbp)))
                    goto bread_err2;
            } else {
                /* This log record is split across physical end of log */
                split_hblks = 0;
                if (blk_no != log->l_logBBsize) {
                    /* some data is before physical end of log */
                    ASSERT(blk_no <= INT_MAX);
                    split_hblks = log->l_logBBsize - (int)blk_no;
                    ASSERT(split_hblks > 0);
                    if ((error = xlog_bread(log, blk_no, split_hblks, hbp)))
                        goto bread_err2;
                }
                bufaddr = XFS_BUF_PTR(hbp);
                XFS_BUF_SET_PTR(hbp, bufaddr + BBTOB(split_hblks),
                        BBTOB(hblks - split_hblks));
                wrapped_hblks = hblks - split_hblks;
                if ((error = xlog_bread(log, 0, wrapped_hblks, hbp)))
                    goto bread_err2;
                XFS_BUF_SET_PTR(hbp, bufaddr, hblks);
            }
            rhead = (xlog_rec_header_t *)XFS_BUF_PTR(hbp);
            ASSERT(INT_GET(rhead->h_magicno, ARCH_CONVERT) == XLOG_HEADER_MAGIC_NUM);
            ASSERT(BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT) <= INT_MAX));
            bblks = (int) BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT));

            /* LR body must have data or it wouldn't have been written */
            ASSERT(bblks > 0);
            blk_no += hblks;                    /* successfully read header */

            if ((INT_GET(rhead->h_magicno, ARCH_CONVERT) != XLOG_HEADER_MAGIC_NUM) ||
                (BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT) > INT_MAX)) ||
                (bblks <= 0)) {
                    error = EFSCORRUPTED;
                    goto bread_err2;
            }

            /* Read in data for log record */
            if (blk_no+bblks <= log->l_logBBsize) {
                if ((error = xlog_bread(log, blk_no, bblks, dbp)))
                    goto bread_err2;
            } else {
                /* This log record is split across physical end of log */
                split_bblks = 0;
                if (blk_no != log->l_logBBsize) {

                    /* some data is before physical end of log */
                    ASSERT(blk_no <= INT_MAX);
                    split_bblks = log->l_logBBsize - (int)blk_no;
                    ASSERT(split_bblks > 0);
                    if ((error = xlog_bread(log, blk_no, split_bblks, dbp)))
                        goto bread_err2;
                }
                bufaddr = XFS_BUF_PTR(dbp);
                XFS_BUF_SET_PTR(dbp, bufaddr + BBTOB(split_bblks),
                        BBTOB(bblks - split_bblks));
                if ((error = xlog_bread(log, wrapped_hblks,
                                        bblks - split_bblks, dbp)))
                    goto bread_err2;
                XFS_BUF_SET_PTR(dbp, bufaddr, XLOG_BIG_RECORD_BSIZE);
            }
            xlog_unpack_data(rhead, XFS_BUF_PTR(dbp), log);
            if ((error = xlog_recover_process_data(log, rhash,
                                                  rhead, XFS_BUF_PTR(dbp),
                                                  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) {
            if ((error = xlog_bread(log, blk_no, hblks, hbp)))
                goto bread_err2;
            rhead = (xlog_rec_header_t *)XFS_BUF_PTR(hbp);
            ASSERT(INT_GET(rhead->h_magicno, ARCH_CONVERT) == XLOG_HEADER_MAGIC_NUM);
            ASSERT(BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT) <= INT_MAX));
            bblks = (int) BTOBB(INT_GET(rhead->h_len, ARCH_CONVERT));
            ASSERT(bblks > 0);
            if ((error = xlog_bread(log, blk_no+hblks, bblks, dbp)))
                goto bread_err2;
            xlog_unpack_data(rhead, XFS_BUF_PTR(dbp), log);
            if ((error = xlog_recover_process_data(log, rhash,
                                                  rhead, XFS_BUF_PTR(dbp),
                                                  pass)))
                goto bread_err2;
            blk_no += (bblks+hblks);
        }
    }

bread_err2:
    xlog_put_bp(dbp);
bread_err1:
    xlog_put_bp(hbp);

    return error;
}