aufs: possible bugfix, allow the nested aufsd between several aufs mounts

[zen-stable.git] / fs / xfs / xfs_trans_buf.c

/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_buf_item.h"
#include "xfs_trans_priv.h"
#include "xfs_error.h"
#include "xfs_rw.h"
#include "xfs_trace.h"

/*
 * Check to see if a buffer matching the given parameters is already
 * a part of the given transaction.
 */
STATIC struct xfs_buf *
xfs_trans_buf_item_match(
        struct xfs_trans        *tp,
        struct xfs_buftarg      *target,
        xfs_daddr_t             blkno,
        int                     len)
{
        struct xfs_log_item_desc *lidp;
        struct xfs_buf_log_item *blip;

        len = BBTOB(len);
        list_for_each_entry(lidp, &tp->t_items, lid_trans) {
                blip = (struct xfs_buf_log_item *)lidp->lid_item;
                if (blip->bli_item.li_type == XFS_LI_BUF &&
                    blip->bli_buf->b_target == target &&
                    XFS_BUF_ADDR(blip->bli_buf) == blkno &&
                    XFS_BUF_COUNT(blip->bli_buf) == len)
                        return blip->bli_buf;
        }

        return NULL;
}

/*
 * Add the locked buffer to the transaction.
 *
 * The buffer must be locked, and it cannot be associated with any
 * transaction.
 *
 * If the buffer does not yet have a buf log item associated with it,
 * then allocate one for it.  Then add the buf item to the transaction.
 */
STATIC void
_xfs_trans_bjoin(
        struct xfs_trans        *tp,
        struct xfs_buf          *bp,
        int                     reset_recur)
{
        struct xfs_buf_log_item *bip;

        ASSERT(bp->b_transp == NULL);

        /*
         * The xfs_buf_log_item pointer is stored in b_fsprivate.  If
         * it doesn't have one yet, then allocate one and initialize it.
         * The checks to see if one is there are in xfs_buf_item_init().
         */
        xfs_buf_item_init(bp, tp->t_mountp);
        bip = bp->b_fspriv;
        ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
        ASSERT(!(bip->bli_format.blf_flags & XFS_BLF_CANCEL));
        ASSERT(!(bip->bli_flags & XFS_BLI_LOGGED));
        if (reset_recur)
                bip->bli_recur = 0;

        /*
         * Take a reference for this transaction on the buf item.
         */
        atomic_inc(&bip->bli_refcount);

        /*
         * Get a log_item_desc to point at the new item.
         */
        xfs_trans_add_item(tp, &bip->bli_item);

        /*
         * Initialize b_fsprivate2 so we can find it with incore_match()
         * in xfs_trans_get_buf() and friends above.
         */
        bp->b_transp = tp;

}

void
xfs_trans_bjoin(
        struct xfs_trans        *tp,
        struct xfs_buf          *bp)
{
        _xfs_trans_bjoin(tp, bp, 0);
        trace_xfs_trans_bjoin(bp->b_fspriv);
}

/*
 * Get and lock the buffer for the caller if it is not already
 * locked within the given transaction.  If it is already locked
 * within the transaction, just increment its lock recursion count
 * and return a pointer to it.
 *
 * If the transaction pointer is NULL, make this just a normal
 * get_buf() call.
 */
xfs_buf_t *
xfs_trans_get_buf(xfs_trans_t   *tp,
                  xfs_buftarg_t *target_dev,
                  xfs_daddr_t   blkno,
                  int           len,
                  uint          flags)
{
        xfs_buf_t               *bp;
        xfs_buf_log_item_t      *bip;

        if (flags == 0)
                flags = XBF_LOCK | XBF_MAPPED;

        /*
         * Default to a normal get_buf() call if the tp is NULL.
         */
        if (tp == NULL)
                return xfs_buf_get(target_dev, blkno, len,
                                   flags | XBF_DONT_BLOCK);

        /*
         * If we find the buffer in the cache with this transaction
         * pointer in its b_fsprivate2 field, then we know we already
         * have it locked.  In this case we just increment the lock
         * recursion count and return the buffer to the caller.
         */
        bp = xfs_trans_buf_item_match(tp, target_dev, blkno, len);
        if (bp != NULL) {
                ASSERT(xfs_buf_islocked(bp));
                if (XFS_FORCED_SHUTDOWN(tp->t_mountp)) {
                        xfs_buf_stale(bp);
                        XFS_BUF_DONE(bp);
                }

                /*
                 * If the buffer is stale then it was binval'ed
                 * since last read.  This doesn't matter since the
                 * caller isn't allowed to use the data anyway.
                 */
                else if (XFS_BUF_ISSTALE(bp))
                        ASSERT(!XFS_BUF_ISDELAYWRITE(bp));

                ASSERT(bp->b_transp == tp);
                bip = bp->b_fspriv;
                ASSERT(bip != NULL);
                ASSERT(atomic_read(&bip->bli_refcount) > 0);
                bip->bli_recur++;
                trace_xfs_trans_get_buf_recur(bip);
                return (bp);
        }

        /*
         * We always specify the XBF_DONT_BLOCK flag within a transaction
         * so that get_buf does not try to push out a delayed write buffer
         * which might cause another transaction to take place (if the
         * buffer was delayed alloc).  Such recursive transactions can
         * easily deadlock with our current transaction as well as cause
         * us to run out of stack space.
         */
        bp = xfs_buf_get(target_dev, blkno, len, flags | XBF_DONT_BLOCK);
        if (bp == NULL) {
                return NULL;
        }

        ASSERT(!bp->b_error);

        _xfs_trans_bjoin(tp, bp, 1);
        trace_xfs_trans_get_buf(bp->b_fspriv);
        return (bp);
}

/*
 * Get and lock the superblock buffer of this file system for the
 * given transaction.
 *
 * We don't need to use incore_match() here, because the superblock
 * buffer is a private buffer which we keep a pointer to in the
 * mount structure.
 */
xfs_buf_t *
xfs_trans_getsb(xfs_trans_t     *tp,
                struct xfs_mount *mp,
                int             flags)
{
        xfs_buf_t               *bp;
        xfs_buf_log_item_t      *bip;

        /*
         * Default to just trying to lock the superblock buffer
         * if tp is NULL.
         */
        if (tp == NULL) {
                return (xfs_getsb(mp, flags));
        }

        /*
         * If the superblock buffer already has this transaction
         * pointer in its b_fsprivate2 field, then we know we already
         * have it locked.  In this case we just increment the lock
         * recursion count and return the buffer to the caller.
         */
        bp = mp->m_sb_bp;
        if (bp->b_transp == tp) {
                bip = bp->b_fspriv;
                ASSERT(bip != NULL);
                ASSERT(atomic_read(&bip->bli_refcount) > 0);
                bip->bli_recur++;
                trace_xfs_trans_getsb_recur(bip);
                return (bp);
        }

        bp = xfs_getsb(mp, flags);
        if (bp == NULL)
                return NULL;

        _xfs_trans_bjoin(tp, bp, 1);
        trace_xfs_trans_getsb(bp->b_fspriv);
        return (bp);
}

#ifdef DEBUG
xfs_buftarg_t *xfs_error_target;
int     xfs_do_error;
int     xfs_req_num;
int     xfs_error_mod = 33;
#endif

/*
 * Get and lock the buffer for the caller if it is not already
 * locked within the given transaction.  If it has not yet been
 * read in, read it from disk. If it is already locked
 * within the transaction and already read in, just increment its
 * lock recursion count and return a pointer to it.
 *
 * If the transaction pointer is NULL, make this just a normal
 * read_buf() call.
 */
int
xfs_trans_read_buf(
        xfs_mount_t     *mp,
        xfs_trans_t     *tp,
        xfs_buftarg_t   *target,
        xfs_daddr_t     blkno,
        int             len,
        uint            flags,
        xfs_buf_t       **bpp)
{
        xfs_buf_t               *bp;
        xfs_buf_log_item_t      *bip;
        int                     error;

        if (flags == 0)
                flags = XBF_LOCK | XBF_MAPPED;

        /*
         * Default to a normal get_buf() call if the tp is NULL.
         */
        if (tp == NULL) {
                bp = xfs_buf_read(target, blkno, len, flags | XBF_DONT_BLOCK);
                if (!bp)
                        return (flags & XBF_TRYLOCK) ?
                                        EAGAIN : XFS_ERROR(ENOMEM);

                if (bp->b_error) {
                        error = bp->b_error;
                        xfs_buf_ioerror_alert(bp, __func__);
                        xfs_buf_relse(bp);
                        return error;
                }
#ifdef DEBUG
                if (xfs_do_error) {
                        if (xfs_error_target == target) {
                                if (((xfs_req_num++) % xfs_error_mod) == 0) {
                                        xfs_buf_relse(bp);
                                        xfs_debug(mp, "Returning error!");
                                        return XFS_ERROR(EIO);
                                }
                        }
                }
#endif
                if (XFS_FORCED_SHUTDOWN(mp))
                        goto shutdown_abort;
                *bpp = bp;
                return 0;
        }

        /*
         * If we find the buffer in the cache with this transaction
         * pointer in its b_fsprivate2 field, then we know we already
         * have it locked.  If it is already read in we just increment
         * the lock recursion count and return the buffer to the caller.
         * If the buffer is not yet read in, then we read it in, increment
         * the lock recursion count, and return it to the caller.
         */
        bp = xfs_trans_buf_item_match(tp, target, blkno, len);
        if (bp != NULL) {
                ASSERT(xfs_buf_islocked(bp));
                ASSERT(bp->b_transp == tp);
                ASSERT(bp->b_fspriv != NULL);
                ASSERT(!bp->b_error);
                if (!(XFS_BUF_ISDONE(bp))) {
                        trace_xfs_trans_read_buf_io(bp, _RET_IP_);
                        ASSERT(!XFS_BUF_ISASYNC(bp));
                        XFS_BUF_READ(bp);
                        xfsbdstrat(tp->t_mountp, bp);
                        error = xfs_buf_iowait(bp);
                        if (error) {
                                xfs_buf_ioerror_alert(bp, __func__);
                                xfs_buf_relse(bp);
                                /*
                                 * We can gracefully recover from most read
                                 * errors. Ones we can't are those that happen
                                 * after the transaction's already dirty.
                                 */
                                if (tp->t_flags & XFS_TRANS_DIRTY)
                                        xfs_force_shutdown(tp->t_mountp,
                                                        SHUTDOWN_META_IO_ERROR);
                                return error;
                        }
                }
                /*
                 * We never locked this buf ourselves, so we shouldn't
                 * brelse it either. Just get out.
                 */
                if (XFS_FORCED_SHUTDOWN(mp)) {
                        trace_xfs_trans_read_buf_shut(bp, _RET_IP_);
                        *bpp = NULL;
                        return XFS_ERROR(EIO);
                }


                bip = bp->b_fspriv;
                bip->bli_recur++;

                ASSERT(atomic_read(&bip->bli_refcount) > 0);
                trace_xfs_trans_read_buf_recur(bip);
                *bpp = bp;
                return 0;
        }

        /*
         * We always specify the XBF_DONT_BLOCK flag within a transaction
         * so that get_buf does not try to push out a delayed write buffer
         * which might cause another transaction to take place (if the
         * buffer was delayed alloc).  Such recursive transactions can
         * easily deadlock with our current transaction as well as cause
         * us to run out of stack space.
         */
        bp = xfs_buf_read(target, blkno, len, flags | XBF_DONT_BLOCK);
        if (bp == NULL) {
                *bpp = NULL;
                return (flags & XBF_TRYLOCK) ?
                                        0 : XFS_ERROR(ENOMEM);
        }
        if (bp->b_error) {
                error = bp->b_error;
                xfs_buf_stale(bp);
                XFS_BUF_DONE(bp);
                xfs_buf_ioerror_alert(bp, __func__);
                if (tp->t_flags & XFS_TRANS_DIRTY)
                        xfs_force_shutdown(tp->t_mountp, SHUTDOWN_META_IO_ERROR);
                xfs_buf_relse(bp);
                return error;
        }
#ifdef DEBUG
        if (xfs_do_error && !(tp->t_flags & XFS_TRANS_DIRTY)) {
                if (xfs_error_target == target) {
                        if (((xfs_req_num++) % xfs_error_mod) == 0) {
                                xfs_force_shutdown(tp->t_mountp,
                                                   SHUTDOWN_META_IO_ERROR);
                                xfs_buf_relse(bp);
                                xfs_debug(mp, "Returning trans error!");
                                return XFS_ERROR(EIO);
                        }
                }
        }
#endif
        if (XFS_FORCED_SHUTDOWN(mp))
                goto shutdown_abort;

        _xfs_trans_bjoin(tp, bp, 1);
        trace_xfs_trans_read_buf(bp->b_fspriv);

        *bpp = bp;
        return 0;

shutdown_abort:
        /*
         * the theory here is that buffer is good but we're
         * bailing out because the filesystem is being forcibly
         * shut down.  So we should leave the b_flags alone since
         * the buffer's not staled and just get out.
         */
#if defined(DEBUG)
        if (XFS_BUF_ISSTALE(bp) && XFS_BUF_ISDELAYWRITE(bp))
                xfs_notice(mp, "about to pop assert, bp == 0x%p", bp);
#endif
        ASSERT((bp->b_flags & (XBF_STALE|XBF_DELWRI)) !=
                                     (XBF_STALE|XBF_DELWRI));

        trace_xfs_trans_read_buf_shut(bp, _RET_IP_);
        xfs_buf_relse(bp);
        *bpp = NULL;
        return XFS_ERROR(EIO);
}


/*
 * Release the buffer bp which was previously acquired with one of the
 * xfs_trans_... buffer allocation routines if the buffer has not
 * been modified within this transaction.  If the buffer is modified
 * within this transaction, do decrement the recursion count but do
 * not release the buffer even if the count goes to 0.  If the buffer is not
 * modified within the transaction, decrement the recursion count and
 * release the buffer if the recursion count goes to 0.
 *
 * If the buffer is to be released and it was not modified before
 * this transaction began, then free the buf_log_item associated with it.
 *
 * If the transaction pointer is NULL, make this just a normal
 * brelse() call.
 */
void
xfs_trans_brelse(xfs_trans_t    *tp,
                 xfs_buf_t      *bp)
{
        xfs_buf_log_item_t      *bip;

        /*
         * Default to a normal brelse() call if the tp is NULL.
         */
        if (tp == NULL) {
                struct xfs_log_item     *lip = bp->b_fspriv;

                ASSERT(bp->b_transp == NULL);

                /*
                 * If there's a buf log item attached to the buffer,
                 * then let the AIL know that the buffer is being
                 * unlocked.
                 */
                if (lip != NULL && lip->li_type == XFS_LI_BUF) {
                        bip = bp->b_fspriv;
                        xfs_trans_unlocked_item(bip->bli_item.li_ailp, lip);
                }
                xfs_buf_relse(bp);
                return;
        }

        ASSERT(bp->b_transp == tp);
        bip = bp->b_fspriv;
        ASSERT(bip->bli_item.li_type == XFS_LI_BUF);
        ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
        ASSERT(!(bip->bli_format.blf_flags & XFS_BLF_CANCEL));
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        trace_xfs_trans_brelse(bip);

        /*
         * If the release is just for a recursive lock,
         * then decrement the count and return.
         */
        if (bip->bli_recur > 0) {
                bip->bli_recur--;
                return;
        }

        /*
         * If the buffer is dirty within this transaction, we can't
         * release it until we commit.
         */
        if (bip->bli_item.li_desc->lid_flags & XFS_LID_DIRTY)
                return;

        /*
         * If the buffer has been invalidated, then we can't release
         * it until the transaction commits to disk unless it is re-dirtied
         * as part of this transaction.  This prevents us from pulling
         * the item from the AIL before we should.
         */
        if (bip->bli_flags & XFS_BLI_STALE)
                return;

        ASSERT(!(bip->bli_flags & XFS_BLI_LOGGED));

        /*
         * Free up the log item descriptor tracking the released item.
         */
        xfs_trans_del_item(&bip->bli_item);

        /*
         * Clear the hold flag in the buf log item if it is set.
         * We wouldn't want the next user of the buffer to
         * get confused.
         */
        if (bip->bli_flags & XFS_BLI_HOLD) {
                bip->bli_flags &= ~XFS_BLI_HOLD;
        }

        /*
         * Drop our reference to the buf log item.
         */
        atomic_dec(&bip->bli_refcount);

        /*
         * If the buf item is not tracking data in the log, then
         * we must free it before releasing the buffer back to the
         * free pool.  Before releasing the buffer to the free pool,
         * clear the transaction pointer in b_fsprivate2 to dissolve
         * its relation to this transaction.
         */
        if (!xfs_buf_item_dirty(bip)) {
/***
                ASSERT(bp->b_pincount == 0);
***/
                ASSERT(atomic_read(&bip->bli_refcount) == 0);
                ASSERT(!(bip->bli_item.li_flags & XFS_LI_IN_AIL));
                ASSERT(!(bip->bli_flags & XFS_BLI_INODE_ALLOC_BUF));
                xfs_buf_item_relse(bp);
                bip = NULL;
        }
        bp->b_transp = NULL;

        /*
         * If we've still got a buf log item on the buffer, then
         * tell the AIL that the buffer is being unlocked.
         */
        if (bip != NULL) {
                xfs_trans_unlocked_item(bip->bli_item.li_ailp,
                                        (xfs_log_item_t*)bip);
        }

        xfs_buf_relse(bp);
        return;
}

/*
 * Mark the buffer as not needing to be unlocked when the buf item's
 * IOP_UNLOCK() routine is called.  The buffer must already be locked
 * and associated with the given transaction.
 */
/* ARGSUSED */
void
xfs_trans_bhold(xfs_trans_t     *tp,
                xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
        ASSERT(!(bip->bli_format.blf_flags & XFS_BLF_CANCEL));
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        bip->bli_flags |= XFS_BLI_HOLD;
        trace_xfs_trans_bhold(bip);
}

/*
 * Cancel the previous buffer hold request made on this buffer
 * for this transaction.
 */
void
xfs_trans_bhold_release(xfs_trans_t     *tp,
                        xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
        ASSERT(!(bip->bli_format.blf_flags & XFS_BLF_CANCEL));
        ASSERT(atomic_read(&bip->bli_refcount) > 0);
        ASSERT(bip->bli_flags & XFS_BLI_HOLD);

        bip->bli_flags &= ~XFS_BLI_HOLD;
        trace_xfs_trans_bhold_release(bip);
}

/*
 * This is called to mark bytes first through last inclusive of the given
 * buffer as needing to be logged when the transaction is committed.
 * The buffer must already be associated with the given transaction.
 *
 * First and last are numbers relative to the beginning of this buffer,
 * so the first byte in the buffer is numbered 0 regardless of the
 * value of b_blkno.
 */
void
xfs_trans_log_buf(xfs_trans_t   *tp,
                  xfs_buf_t     *bp,
                  uint          first,
                  uint          last)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT((first <= last) && (last < XFS_BUF_COUNT(bp)));
        ASSERT(bp->b_iodone == NULL ||
               bp->b_iodone == xfs_buf_iodone_callbacks);

        /*
         * Mark the buffer as needing to be written out eventually,
         * and set its iodone function to remove the buffer's buf log
         * item from the AIL and free it when the buffer is flushed
         * to disk.  See xfs_buf_attach_iodone() for more details
         * on li_cb and xfs_buf_iodone_callbacks().
         * If we end up aborting this transaction, we trap this buffer
         * inside the b_bdstrat callback so that this won't get written to
         * disk.
         */
        XFS_BUF_DONE(bp);

        ASSERT(atomic_read(&bip->bli_refcount) > 0);
        bp->b_iodone = xfs_buf_iodone_callbacks;
        bip->bli_item.li_cb = xfs_buf_iodone;

        xfs_buf_delwri_queue(bp);

        trace_xfs_trans_log_buf(bip);

        /*
         * If we invalidated the buffer within this transaction, then
         * cancel the invalidation now that we're dirtying the buffer
         * again.  There are no races with the code in xfs_buf_item_unpin(),
         * because we have a reference to the buffer this entire time.
         */
        if (bip->bli_flags & XFS_BLI_STALE) {
                bip->bli_flags &= ~XFS_BLI_STALE;
                ASSERT(XFS_BUF_ISSTALE(bp));
                XFS_BUF_UNSTALE(bp);
                bip->bli_format.blf_flags &= ~XFS_BLF_CANCEL;
        }

        tp->t_flags |= XFS_TRANS_DIRTY;
        bip->bli_item.li_desc->lid_flags |= XFS_LID_DIRTY;
        bip->bli_flags |= XFS_BLI_LOGGED;
        xfs_buf_item_log(bip, first, last);
}


/*
 * This called to invalidate a buffer that is being used within
 * a transaction.  Typically this is because the blocks in the
 * buffer are being freed, so we need to prevent it from being
 * written out when we're done.  Allowing it to be written again
 * might overwrite data in the free blocks if they are reallocated
 * to a file.
 *
 * We prevent the buffer from being written out by clearing the
 * B_DELWRI flag.  We can't always
 * get rid of the buf log item at this point, though, because
 * the buffer may still be pinned by another transaction.  If that
 * is the case, then we'll wait until the buffer is committed to
 * disk for the last time (we can tell by the ref count) and
 * free it in xfs_buf_item_unpin().  Until it is cleaned up we
 * will keep the buffer locked so that the buffer and buf log item
 * are not reused.
 */
void
xfs_trans_binval(
        xfs_trans_t     *tp,
        xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        trace_xfs_trans_binval(bip);

        if (bip->bli_flags & XFS_BLI_STALE) {
                /*
                 * If the buffer is already invalidated, then
                 * just return.
                 */
                ASSERT(!(XFS_BUF_ISDELAYWRITE(bp)));
                ASSERT(XFS_BUF_ISSTALE(bp));
                ASSERT(!(bip->bli_flags & (XFS_BLI_LOGGED | XFS_BLI_DIRTY)));
                ASSERT(!(bip->bli_format.blf_flags & XFS_BLF_INODE_BUF));
                ASSERT(bip->bli_format.blf_flags & XFS_BLF_CANCEL);
                ASSERT(bip->bli_item.li_desc->lid_flags & XFS_LID_DIRTY);
                ASSERT(tp->t_flags & XFS_TRANS_DIRTY);
                return;
        }

        /*
         * Clear the dirty bit in the buffer and set the STALE flag
         * in the buf log item.  The STALE flag will be used in
         * xfs_buf_item_unpin() to determine if it should clean up
         * when the last reference to the buf item is given up.
         * We set the XFS_BLF_CANCEL flag in the buf log format structure
         * and log the buf item.  This will be used at recovery time
         * to determine that copies of the buffer in the log before
         * this should not be replayed.
         * We mark the item descriptor and the transaction dirty so
         * that we'll hold the buffer until after the commit.
         *
         * Since we're invalidating the buffer, we also clear the state
         * about which parts of the buffer have been logged.  We also
         * clear the flag indicating that this is an inode buffer since
         * the data in the buffer will no longer be valid.
         *
         * We set the stale bit in the buffer as well since we're getting
         * rid of it.
         */
        xfs_buf_stale(bp);
        bip->bli_flags |= XFS_BLI_STALE;
        bip->bli_flags &= ~(XFS_BLI_INODE_BUF | XFS_BLI_LOGGED | XFS_BLI_DIRTY);
        bip->bli_format.blf_flags &= ~XFS_BLF_INODE_BUF;
        bip->bli_format.blf_flags |= XFS_BLF_CANCEL;
        memset((char *)(bip->bli_format.blf_data_map), 0,
              (bip->bli_format.blf_map_size * sizeof(uint)));
        bip->bli_item.li_desc->lid_flags |= XFS_LID_DIRTY;
        tp->t_flags |= XFS_TRANS_DIRTY;
}

/*
 * This call is used to indicate that the buffer contains on-disk inodes which
 * must be handled specially during recovery.  They require special handling
 * because only the di_next_unlinked from the inodes in the buffer should be
 * recovered.  The rest of the data in the buffer is logged via the inodes
 * themselves.
 *
 * All we do is set the XFS_BLI_INODE_BUF flag in the items flags so it can be
 * transferred to the buffer's log format structure so that we'll know what to
 * do at recovery time.
 */
void
xfs_trans_inode_buf(
        xfs_trans_t     *tp,
        xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        bip->bli_flags |= XFS_BLI_INODE_BUF;
}

/*
 * This call is used to indicate that the buffer is going to
 * be staled and was an inode buffer. This means it gets
 * special processing during unpin - where any inodes 
 * associated with the buffer should be removed from ail.
 * There is also special processing during recovery,
 * any replay of the inodes in the buffer needs to be
 * prevented as the buffer may have been reused.
 */
void
xfs_trans_stale_inode_buf(
        xfs_trans_t     *tp,
        xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        bip->bli_flags |= XFS_BLI_STALE_INODE;
        bip->bli_item.li_cb = xfs_buf_iodone;
}

/*
 * Mark the buffer as being one which contains newly allocated
 * inodes.  We need to make sure that even if this buffer is
 * relogged as an 'inode buf' we still recover all of the inode
 * images in the face of a crash.  This works in coordination with
 * xfs_buf_item_committed() to ensure that the buffer remains in the
 * AIL at its original location even after it has been relogged.
 */
/* ARGSUSED */
void
xfs_trans_inode_alloc_buf(
        xfs_trans_t     *tp,
        xfs_buf_t       *bp)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        bip->bli_flags |= XFS_BLI_INODE_ALLOC_BUF;
}


/*
 * Similar to xfs_trans_inode_buf(), this marks the buffer as a cluster of
 * dquots. However, unlike in inode buffer recovery, dquot buffers get
 * recovered in their entirety. (Hence, no XFS_BLI_DQUOT_ALLOC_BUF flag).
 * The only thing that makes dquot buffers different from regular
 * buffers is that we must not replay dquot bufs when recovering
 * if a _corresponding_ quotaoff has happened. We also have to distinguish
 * between usr dquot bufs and grp dquot bufs, because usr and grp quotas
 * can be turned off independently.
 */
/* ARGSUSED */
void
xfs_trans_dquot_buf(
        xfs_trans_t     *tp,
        xfs_buf_t       *bp,
        uint            type)
{
        xfs_buf_log_item_t      *bip = bp->b_fspriv;

        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
        ASSERT(type == XFS_BLF_UDQUOT_BUF ||
               type == XFS_BLF_PDQUOT_BUF ||
               type == XFS_BLF_GDQUOT_BUF);
        ASSERT(atomic_read(&bip->bli_refcount) > 0);

        bip->bli_format.blf_flags |= type;
}