xfs_trans.c

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/*
 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
 * Copyright (C) 2010 Red Hat, 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_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_da_btree.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_btree.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_extent_busy.h"
#include "xfs_bmap.h"
#include "xfs_quota.h"
#include "xfs_trans_priv.h"
#include "xfs_trans_space.h"
#include "xfs_inode_item.h"
#include "xfs_trace.h"

kmem_zone_t *xfs_trans_zone;
kmem_zone_t *xfs_log_item_desc_zone;


/*
 * Various log reservation values.
 *
 * These are based on the size of the file system block because that is what
 * most transactions manipulate.  Each adds in an additional 128 bytes per
 * item logged to try to account for the overhead of the transaction mechanism.
 *
 * Note:  Most of the reservations underestimate the number of allocation
 * groups into which they could free extents in the xfs_bmap_finish() call.
 * This is because the number in the worst case is quite high and quite
 * unusual.  In order to fix this we need to change xfs_bmap_finish() to free
 * extents in only a single AG at a time.  This will require changes to the
 * EFI code as well, however, so that the EFI for the extents not freed is
 * logged again in each transaction.  See SGI PV #261917.
 *
 * Reservation functions here avoid a huge stack in xfs_trans_init due to
 * register overflow from temporaries in the calculations.
 */


/*
 * In a write transaction we can allocate a maximum of 2
 * extents.  This gives:
 *    the inode getting the new extents: inode size
 *    the inode's bmap btree: max depth * block size
 *    the agfs of the ags from which the extents are allocated: 2 * sector
 *    the superblock free block counter: sector size
 *    the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
 * And the bmap_finish transaction can free bmap blocks in a join:
 *    the agfs of the ags containing the blocks: 2 * sector size
 *    the agfls of the ags containing the blocks: 2 * sector size
 *    the super block free block counter: sector size
 *    the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_write_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             XFS_FSB_TO_B(mp, XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK)) +
             2 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 2) +
             128 * (4 + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) +
                XFS_ALLOCFREE_LOG_COUNT(mp, 2))),
            (2 * mp->m_sb.sb_sectsize +
             2 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 2) +
             128 * (5 + XFS_ALLOCFREE_LOG_COUNT(mp, 2))));
}

/*
 * In truncating a file we free up to two extents at once.  We can modify:
 *    the inode being truncated: inode size
 *    the inode's bmap btree: (max depth + 1) * block size
 * And the bmap_finish transaction can free the blocks and bmap blocks:
 *    the agf for each of the ags: 4 * sector size
 *    the agfl for each of the ags: 4 * sector size
 *    the super block to reflect the freed blocks: sector size
 *    worst case split in allocation btrees per extent assuming 4 extents:
 *      4 exts * 2 trees * (2 * max depth - 1) * block size
 *    the inode btree: max depth * blocksize
 *    the allocation btrees: 2 trees * (max depth - 1) * block size
 */
STATIC uint
xfs_calc_itruncate_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             XFS_FSB_TO_B(mp, XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1) +
             128 * (2 + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK))),
            (4 * mp->m_sb.sb_sectsize +
             4 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 4) +
             128 * (9 + XFS_ALLOCFREE_LOG_COUNT(mp, 4)) +
             128 * 5 +
             XFS_ALLOCFREE_LOG_RES(mp, 1) +
             128 * (2 + XFS_IALLOC_BLOCKS(mp) + mp->m_in_maxlevels +
                XFS_ALLOCFREE_LOG_COUNT(mp, 1))));
}

/*
 * In renaming a files we can modify:
 *    the four inodes involved: 4 * inode size
 *    the two directory btrees: 2 * (max depth + v2) * dir block size
 *    the two directory bmap btrees: 2 * max depth * block size
 * And the bmap_finish transaction can free dir and bmap blocks (two sets
 *  of bmap blocks) giving:
 *    the agf for the ags in which the blocks live: 3 * sector size
 *    the agfl for the ags in which the blocks live: 3 * sector size
 *    the superblock for the free block count: sector size
 *    the allocation btrees: 3 exts * 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_rename_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((4 * mp->m_sb.sb_inodesize +
             2 * XFS_DIROP_LOG_RES(mp) +
             128 * (4 + 2 * XFS_DIROP_LOG_COUNT(mp))),
            (3 * mp->m_sb.sb_sectsize +
             3 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 3) +
             128 * (7 + XFS_ALLOCFREE_LOG_COUNT(mp, 3))));
}

/*
 * For creating a link to an inode:
 *    the parent directory inode: inode size
 *    the linked inode: inode size
 *    the directory btree could split: (max depth + v2) * dir block size
 *    the directory bmap btree could join or split: (max depth + v2) * blocksize
 * And the bmap_finish transaction can free some bmap blocks giving:
 *    the agf for the ag in which the blocks live: sector size
 *    the agfl for the ag in which the blocks live: sector size
 *    the superblock for the free block count: sector size
 *    the allocation btrees: 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_link_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             mp->m_sb.sb_inodesize +
             XFS_DIROP_LOG_RES(mp) +
             128 * (2 + XFS_DIROP_LOG_COUNT(mp))),
            (mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 1) +
             128 * (3 + XFS_ALLOCFREE_LOG_COUNT(mp, 1))));
}

/*
 * For removing a directory entry we can modify:
 *    the parent directory inode: inode size
 *    the removed inode: inode size
 *    the directory btree could join: (max depth + v2) * dir block size
 *    the directory bmap btree could join or split: (max depth + v2) * blocksize
 * And the bmap_finish transaction can free the dir and bmap blocks giving:
 *    the agf for the ag in which the blocks live: 2 * sector size
 *    the agfl for the ag in which the blocks live: 2 * sector size
 *    the superblock for the free block count: sector size
 *    the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_remove_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             mp->m_sb.sb_inodesize +
             XFS_DIROP_LOG_RES(mp) +
             128 * (2 + XFS_DIROP_LOG_COUNT(mp))),
            (2 * mp->m_sb.sb_sectsize +
             2 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 2) +
             128 * (5 + XFS_ALLOCFREE_LOG_COUNT(mp, 2))));
}

/*
 * For symlink we can modify:
 *    the parent directory inode: inode size
 *    the new inode: inode size
 *    the inode btree entry: 1 block
 *    the directory btree: (max depth + v2) * dir block size
 *    the directory inode's bmap btree: (max depth + v2) * block size
 *    the blocks for the symlink: 1 kB
 * Or in the first xact we allocate some inodes giving:
 *    the agi and agf of the ag getting the new inodes: 2 * sectorsize
 *    the inode blocks allocated: XFS_IALLOC_BLOCKS * blocksize
 *    the inode btree: max depth * blocksize
 *    the allocation btrees: 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_symlink_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             mp->m_sb.sb_inodesize +
             XFS_FSB_TO_B(mp, 1) +
             XFS_DIROP_LOG_RES(mp) +
             1024 +
             128 * (4 + XFS_DIROP_LOG_COUNT(mp))),
            (2 * mp->m_sb.sb_sectsize +
             XFS_FSB_TO_B(mp, XFS_IALLOC_BLOCKS(mp)) +
             XFS_FSB_TO_B(mp, mp->m_in_maxlevels) +
             XFS_ALLOCFREE_LOG_RES(mp, 1) +
             128 * (2 + XFS_IALLOC_BLOCKS(mp) + mp->m_in_maxlevels +
                XFS_ALLOCFREE_LOG_COUNT(mp, 1))));
}

/*
 * For create we can modify:
 *    the parent directory inode: inode size
 *    the new inode: inode size
 *    the inode btree entry: block size
 *    the superblock for the nlink flag: sector size
 *    the directory btree: (max depth + v2) * dir block size
 *    the directory inode's bmap btree: (max depth + v2) * block size
 * Or in the first xact we allocate some inodes giving:
 *    the agi and agf of the ag getting the new inodes: 2 * sectorsize
 *    the superblock for the nlink flag: sector size
 *    the inode blocks allocated: XFS_IALLOC_BLOCKS * blocksize
 *    the inode btree: max depth * blocksize
 *    the allocation btrees: 2 trees * (max depth - 1) * block size
 */
STATIC uint
xfs_calc_create_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             mp->m_sb.sb_inodesize +
             mp->m_sb.sb_sectsize +
             XFS_FSB_TO_B(mp, 1) +
             XFS_DIROP_LOG_RES(mp) +
             128 * (3 + XFS_DIROP_LOG_COUNT(mp))),
            (3 * mp->m_sb.sb_sectsize +
             XFS_FSB_TO_B(mp, XFS_IALLOC_BLOCKS(mp)) +
             XFS_FSB_TO_B(mp, mp->m_in_maxlevels) +
             XFS_ALLOCFREE_LOG_RES(mp, 1) +
             128 * (2 + XFS_IALLOC_BLOCKS(mp) + mp->m_in_maxlevels +
                XFS_ALLOCFREE_LOG_COUNT(mp, 1))));
}

/*
 * Making a new directory is the same as creating a new file.
 */
STATIC uint
xfs_calc_mkdir_reservation(
    struct xfs_mount    *mp)
{
    return xfs_calc_create_reservation(mp);
}

/*
 * In freeing an inode we can modify:
 *    the inode being freed: inode size
 *    the super block free inode counter: sector size
 *    the agi hash list and counters: sector size
 *    the inode btree entry: block size
 *    the on disk inode before ours in the agi hash list: inode cluster size
 *    the inode btree: max depth * blocksize
 *    the allocation btrees: 2 trees * (max depth - 1) * block size
 */
STATIC uint
xfs_calc_ifree_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        mp->m_sb.sb_inodesize +
        mp->m_sb.sb_sectsize +
        mp->m_sb.sb_sectsize +
        XFS_FSB_TO_B(mp, 1) +
        MAX((__uint16_t)XFS_FSB_TO_B(mp, 1),
            XFS_INODE_CLUSTER_SIZE(mp)) +
        128 * 5 +
        XFS_ALLOCFREE_LOG_RES(mp, 1) +
        128 * (2 + XFS_IALLOC_BLOCKS(mp) + mp->m_in_maxlevels +
               XFS_ALLOCFREE_LOG_COUNT(mp, 1));
}

/*
 * When only changing the inode we log the inode and possibly the superblock
 * We also add a bit of slop for the transaction stuff.
 */
STATIC uint
xfs_calc_ichange_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        mp->m_sb.sb_inodesize +
        mp->m_sb.sb_sectsize +
        512;

}

/*
 * Growing the data section of the filesystem.
 *  superblock
 *  agi and agf
 *  allocation btrees
 */
STATIC uint
xfs_calc_growdata_reservation(
    struct xfs_mount    *mp)
{
    return mp->m_sb.sb_sectsize * 3 +
        XFS_ALLOCFREE_LOG_RES(mp, 1) +
        128 * (3 + XFS_ALLOCFREE_LOG_COUNT(mp, 1));
}

/*
 * Growing the rt section of the filesystem.
 * In the first set of transactions (ALLOC) we allocate space to the
 * bitmap or summary files.
 *  superblock: sector size
 *  agf of the ag from which the extent is allocated: sector size
 *  bmap btree for bitmap/summary inode: max depth * blocksize
 *  bitmap/summary inode: inode size
 *  allocation btrees for 1 block alloc: 2 * (2 * maxdepth - 1) * blocksize
 */
STATIC uint
xfs_calc_growrtalloc_reservation(
    struct xfs_mount    *mp)
{
    return 2 * mp->m_sb.sb_sectsize +
        XFS_FSB_TO_B(mp, XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK)) +
        mp->m_sb.sb_inodesize +
        XFS_ALLOCFREE_LOG_RES(mp, 1) +
        128 * (3 + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) +
               XFS_ALLOCFREE_LOG_COUNT(mp, 1));
}

/*
 * Growing the rt section of the filesystem.
 * In the second set of transactions (ZERO) we zero the new metadata blocks.
 *  one bitmap/summary block: blocksize
 */
STATIC uint
xfs_calc_growrtzero_reservation(
    struct xfs_mount    *mp)
{
    return mp->m_sb.sb_blocksize + 128;
}

/*
 * Growing the rt section of the filesystem.
 * In the third set of transactions (FREE) we update metadata without
 * allocating any new blocks.
 *  superblock: sector size
 *  bitmap inode: inode size
 *  summary inode: inode size
 *  one bitmap block: blocksize
 *  summary blocks: new summary size
 */
STATIC uint
xfs_calc_growrtfree_reservation(
    struct xfs_mount    *mp)
{
    return mp->m_sb.sb_sectsize +
        2 * mp->m_sb.sb_inodesize +
        mp->m_sb.sb_blocksize +
        mp->m_rsumsize +
        128 * 5;
}

/*
 * Logging the inode modification timestamp on a synchronous write.
 *  inode
 */
STATIC uint
xfs_calc_swrite_reservation(
    struct xfs_mount    *mp)
{
    return mp->m_sb.sb_inodesize + 128;
}

/*
 * Logging the inode mode bits when writing a setuid/setgid file
 *  inode
 */
STATIC uint
xfs_calc_writeid_reservation(xfs_mount_t *mp)
{
    return mp->m_sb.sb_inodesize + 128;
}

/*
 * Converting the inode from non-attributed to attributed.
 *  the inode being converted: inode size
 *  agf block and superblock (for block allocation)
 *  the new block (directory sized)
 *  bmap blocks for the new directory block
 *  allocation btrees
 */
STATIC uint
xfs_calc_addafork_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        mp->m_sb.sb_inodesize +
        mp->m_sb.sb_sectsize * 2 +
        mp->m_dirblksize +
        XFS_FSB_TO_B(mp, XFS_DAENTER_BMAP1B(mp, XFS_DATA_FORK) + 1) +
        XFS_ALLOCFREE_LOG_RES(mp, 1) +
        128 * (4 + XFS_DAENTER_BMAP1B(mp, XFS_DATA_FORK) + 1 +
               XFS_ALLOCFREE_LOG_COUNT(mp, 1));
}

/*
 * Removing the attribute fork of a file
 *    the inode being truncated: inode size
 *    the inode's bmap btree: max depth * block size
 * And the bmap_finish transaction can free the blocks and bmap blocks:
 *    the agf for each of the ags: 4 * sector size
 *    the agfl for each of the ags: 4 * sector size
 *    the super block to reflect the freed blocks: sector size
 *    worst case split in allocation btrees per extent assuming 4 extents:
 *      4 exts * 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_attrinval_reservation(
    struct xfs_mount    *mp)
{
    return MAX((mp->m_sb.sb_inodesize +
            XFS_FSB_TO_B(mp, XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK)) +
            128 * (1 + XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK))),
           (4 * mp->m_sb.sb_sectsize +
            4 * mp->m_sb.sb_sectsize +
            mp->m_sb.sb_sectsize +
            XFS_ALLOCFREE_LOG_RES(mp, 4) +
            128 * (9 + XFS_ALLOCFREE_LOG_COUNT(mp, 4))));
}

/*
 * Setting an attribute.
 *  the inode getting the attribute
 *  the superblock for allocations
 *  the agfs extents are allocated from
 *  the attribute btree * max depth
 *  the inode allocation btree
 * Since attribute transaction space is dependent on the size of the attribute,
 * the calculation is done partially at mount time and partially at runtime.
 */
STATIC uint
xfs_calc_attrset_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        mp->m_sb.sb_inodesize +
        mp->m_sb.sb_sectsize +
        XFS_FSB_TO_B(mp, XFS_DA_NODE_MAXDEPTH) +
        128 * (2 + XFS_DA_NODE_MAXDEPTH);
}

/*
 * Removing an attribute.
 *    the inode: inode size
 *    the attribute btree could join: max depth * block size
 *    the inode bmap btree could join or split: max depth * block size
 * And the bmap_finish transaction can free the attr blocks freed giving:
 *    the agf for the ag in which the blocks live: 2 * sector size
 *    the agfl for the ag in which the blocks live: 2 * sector size
 *    the superblock for the free block count: sector size
 *    the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
 */
STATIC uint
xfs_calc_attrrm_reservation(
    struct xfs_mount    *mp)
{
    return XFS_DQUOT_LOGRES(mp) +
        MAX((mp->m_sb.sb_inodesize +
             XFS_FSB_TO_B(mp, XFS_DA_NODE_MAXDEPTH) +
             XFS_FSB_TO_B(mp, XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK)) +
             128 * (1 + XFS_DA_NODE_MAXDEPTH +
                XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK))),
            (2 * mp->m_sb.sb_sectsize +
             2 * mp->m_sb.sb_sectsize +
             mp->m_sb.sb_sectsize +
             XFS_ALLOCFREE_LOG_RES(mp, 2) +
             128 * (5 + XFS_ALLOCFREE_LOG_COUNT(mp, 2))));
}

/*
 * Clearing a bad agino number in an agi hash bucket.
 */
STATIC uint
xfs_calc_clear_agi_bucket_reservation(
    struct xfs_mount    *mp)
{
    return mp->m_sb.sb_sectsize + 128;
}

/*
 * Initialize the precomputed transaction reservation values
 * in the mount structure.
 */
void
xfs_trans_init(
    struct xfs_mount    *mp)
{
    struct xfs_trans_reservations *resp = &mp->m_reservations;

    resp->tr_write = xfs_calc_write_reservation(mp);
    resp->tr_itruncate = xfs_calc_itruncate_reservation(mp);
    resp->tr_rename = xfs_calc_rename_reservation(mp);
    resp->tr_link = xfs_calc_link_reservation(mp);
    resp->tr_remove = xfs_calc_remove_reservation(mp);
    resp->tr_symlink = xfs_calc_symlink_reservation(mp);
    resp->tr_create = xfs_calc_create_reservation(mp);
    resp->tr_mkdir = xfs_calc_mkdir_reservation(mp);
    resp->tr_ifree = xfs_calc_ifree_reservation(mp);
    resp->tr_ichange = xfs_calc_ichange_reservation(mp);
    resp->tr_growdata = xfs_calc_growdata_reservation(mp);
    resp->tr_swrite = xfs_calc_swrite_reservation(mp);
    resp->tr_writeid = xfs_calc_writeid_reservation(mp);
    resp->tr_addafork = xfs_calc_addafork_reservation(mp);
    resp->tr_attrinval = xfs_calc_attrinval_reservation(mp);
    resp->tr_attrset = xfs_calc_attrset_reservation(mp);
    resp->tr_attrrm = xfs_calc_attrrm_reservation(mp);
    resp->tr_clearagi = xfs_calc_clear_agi_bucket_reservation(mp);
    resp->tr_growrtalloc = xfs_calc_growrtalloc_reservation(mp);
    resp->tr_growrtzero = xfs_calc_growrtzero_reservation(mp);
    resp->tr_growrtfree = xfs_calc_growrtfree_reservation(mp);
}

/*
 * This routine is called to allocate a transaction structure.
 * The type parameter indicates the type of the transaction.  These
 * are enumerated in xfs_trans.h.
 *
 * Dynamically allocate the transaction structure from the transaction
 * zone, initialize it, and return it to the caller.
 */
xfs_trans_t *
xfs_trans_alloc(
    xfs_mount_t *mp,
    uint        type)
{
    xfs_trans_t     *tp;

    sb_start_intwrite(mp->m_super);
    tp = _xfs_trans_alloc(mp, type, KM_SLEEP);
    tp->t_flags |= XFS_TRANS_FREEZE_PROT;
    return tp;
}

xfs_trans_t *
_xfs_trans_alloc(
    xfs_mount_t *mp,
    uint        type,
    xfs_km_flags_t  memflags)
{
    xfs_trans_t *tp;

    WARN_ON(mp->m_super->s_writers.frozen == SB_FREEZE_COMPLETE);
    atomic_inc(&mp->m_active_trans);

    tp = kmem_zone_zalloc(xfs_trans_zone, memflags);
    tp->t_magic = XFS_TRANS_MAGIC;
    tp->t_type = type;
    tp->t_mountp = mp;
    INIT_LIST_HEAD(&tp->t_items);
    INIT_LIST_HEAD(&tp->t_busy);
    return tp;
}

/*
 * Free the transaction structure.  If there is more clean up
 * to do when the structure is freed, add it here.
 */
STATIC void
xfs_trans_free(
    struct xfs_trans    *tp)
{
    xfs_extent_busy_sort(&tp->t_busy);
    xfs_extent_busy_clear(tp->t_mountp, &tp->t_busy, false);

    atomic_dec(&tp->t_mountp->m_active_trans);
    if (tp->t_flags & XFS_TRANS_FREEZE_PROT)
        sb_end_intwrite(tp->t_mountp->m_super);
    xfs_trans_free_dqinfo(tp);
    kmem_zone_free(xfs_trans_zone, tp);
}

/*
 * This is called to create a new transaction which will share the
 * permanent log reservation of the given transaction.  The remaining
 * unused block and rt extent reservations are also inherited.  This
 * implies that the original transaction is no longer allowed to allocate
 * blocks.  Locks and log items, however, are no inherited.  They must
 * be added to the new transaction explicitly.
 */
xfs_trans_t *
xfs_trans_dup(
    xfs_trans_t *tp)
{
    xfs_trans_t *ntp;

    ntp = kmem_zone_zalloc(xfs_trans_zone, KM_SLEEP);

    /*
     * Initialize the new transaction structure.
     */
    ntp->t_magic = XFS_TRANS_MAGIC;
    ntp->t_type = tp->t_type;
    ntp->t_mountp = tp->t_mountp;
    INIT_LIST_HEAD(&ntp->t_items);
    INIT_LIST_HEAD(&ntp->t_busy);

    ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
    ASSERT(tp->t_ticket != NULL);

    ntp->t_flags = XFS_TRANS_PERM_LOG_RES |
               (tp->t_flags & XFS_TRANS_RESERVE) |
               (tp->t_flags & XFS_TRANS_FREEZE_PROT);
    /* We gave our writer reference to the new transaction */
    tp->t_flags &= ~XFS_TRANS_FREEZE_PROT;
    ntp->t_ticket = xfs_log_ticket_get(tp->t_ticket);
    ntp->t_blk_res = tp->t_blk_res - tp->t_blk_res_used;
    tp->t_blk_res = tp->t_blk_res_used;
    ntp->t_rtx_res = tp->t_rtx_res - tp->t_rtx_res_used;
    tp->t_rtx_res = tp->t_rtx_res_used;
    ntp->t_pflags = tp->t_pflags;

    xfs_trans_dup_dqinfo(tp, ntp);

    atomic_inc(&tp->t_mountp->m_active_trans);
    return ntp;
}

/*
 * This is called to reserve free disk blocks and log space for the
 * given transaction.  This must be done before allocating any resources
 * within the transaction.
 *
 * This will return ENOSPC if there are not enough blocks available.
 * It will sleep waiting for available log space.
 * The only valid value for the flags parameter is XFS_RES_LOG_PERM, which
 * is used by long running transactions.  If any one of the reservations
 * fails then they will all be backed out.
 *
 * This does not do quota reservations. That typically is done by the
 * caller afterwards.
 */
int
xfs_trans_reserve(
    xfs_trans_t *tp,
    uint        blocks,
    uint        logspace,
    uint        rtextents,
    uint        flags,
    uint        logcount)
{
    int     error = 0;
    int     rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;

    /* Mark this thread as being in a transaction */
    current_set_flags_nested(&tp->t_pflags, PF_FSTRANS);

    /*
     * Attempt to reserve the needed disk blocks by decrementing
     * the number needed from the number available.  This will
     * fail if the count would go below zero.
     */
    if (blocks > 0) {
        error = xfs_icsb_modify_counters(tp->t_mountp, XFS_SBS_FDBLOCKS,
                      -((int64_t)blocks), rsvd);
        if (error != 0) {
            current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
            return (XFS_ERROR(ENOSPC));
        }
        tp->t_blk_res += blocks;
    }

    /*
     * Reserve the log space needed for this transaction.
     */
    if (logspace > 0) {
        bool    permanent = false;

        ASSERT(tp->t_log_res == 0 || tp->t_log_res == logspace);
        ASSERT(tp->t_log_count == 0 || tp->t_log_count == logcount);

        if (flags & XFS_TRANS_PERM_LOG_RES) {
            tp->t_flags |= XFS_TRANS_PERM_LOG_RES;
            permanent = true;
        } else {
            ASSERT(tp->t_ticket == NULL);
            ASSERT(!(tp->t_flags & XFS_TRANS_PERM_LOG_RES));
        }

        if (tp->t_ticket != NULL) {
            ASSERT(flags & XFS_TRANS_PERM_LOG_RES);
            error = xfs_log_regrant(tp->t_mountp, tp->t_ticket);
        } else {
            error = xfs_log_reserve(tp->t_mountp, logspace,
                        logcount, &tp->t_ticket,
                        XFS_TRANSACTION, permanent,
                        tp->t_type);
        }

        if (error)
            goto undo_blocks;

        tp->t_log_res = logspace;
        tp->t_log_count = logcount;
    }

    /*
     * Attempt to reserve the needed realtime extents by decrementing
     * the number needed from the number available.  This will
     * fail if the count would go below zero.
     */
    if (rtextents > 0) {
        error = xfs_mod_incore_sb(tp->t_mountp, XFS_SBS_FREXTENTS,
                      -((int64_t)rtextents), rsvd);
        if (error) {
            error = XFS_ERROR(ENOSPC);
            goto undo_log;
        }
        tp->t_rtx_res += rtextents;
    }

    return 0;

    /*
     * Error cases jump to one of these labels to undo any
     * reservations which have already been performed.
     */
undo_log:
    if (logspace > 0) {
        int     log_flags;

        if (flags & XFS_TRANS_PERM_LOG_RES) {
            log_flags = XFS_LOG_REL_PERM_RESERV;
        } else {
            log_flags = 0;
        }
        xfs_log_done(tp->t_mountp, tp->t_ticket, NULL, log_flags);
        tp->t_ticket = NULL;
        tp->t_log_res = 0;
        tp->t_flags &= ~XFS_TRANS_PERM_LOG_RES;
    }

undo_blocks:
    if (blocks > 0) {
        xfs_icsb_modify_counters(tp->t_mountp, XFS_SBS_FDBLOCKS,
                     (int64_t)blocks, rsvd);
        tp->t_blk_res = 0;
    }

    current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);

    return error;
}

/*
 * Record the indicated change to the given field for application
 * to the file system's superblock when the transaction commits.
 * For now, just store the change in the transaction structure.
 *
 * Mark the transaction structure to indicate that the superblock
 * needs to be updated before committing.
 *
 * Because we may not be keeping track of allocated/free inodes and
 * used filesystem blocks in the superblock, we do not mark the
 * superblock dirty in this transaction if we modify these fields.
 * We still need to update the transaction deltas so that they get
 * applied to the incore superblock, but we don't want them to
 * cause the superblock to get locked and logged if these are the
 * only fields in the superblock that the transaction modifies.
 */
void
xfs_trans_mod_sb(
    xfs_trans_t *tp,
    uint        field,
    int64_t     delta)
{
    uint32_t    flags = (XFS_TRANS_DIRTY|XFS_TRANS_SB_DIRTY);
    xfs_mount_t *mp = tp->t_mountp;

    switch (field) {
    case XFS_TRANS_SB_ICOUNT:
        tp->t_icount_delta += delta;
        if (xfs_sb_version_haslazysbcount(&mp->m_sb))
            flags &= ~XFS_TRANS_SB_DIRTY;
        break;
    case XFS_TRANS_SB_IFREE:
        tp->t_ifree_delta += delta;
        if (xfs_sb_version_haslazysbcount(&mp->m_sb))
            flags &= ~XFS_TRANS_SB_DIRTY;
        break;
    case XFS_TRANS_SB_FDBLOCKS:
        /*
         * Track the number of blocks allocated in the
         * transaction.  Make sure it does not exceed the
         * number reserved.
         */
        if (delta < 0) {
            tp->t_blk_res_used += (uint)-delta;
            ASSERT(tp->t_blk_res_used <= tp->t_blk_res);
        }
        tp->t_fdblocks_delta += delta;
        if (xfs_sb_version_haslazysbcount(&mp->m_sb))
            flags &= ~XFS_TRANS_SB_DIRTY;
        break;
    case XFS_TRANS_SB_RES_FDBLOCKS:
        /*
         * The allocation has already been applied to the
         * in-core superblock's counter.  This should only
         * be applied to the on-disk superblock.
         */
        ASSERT(delta < 0);
        tp->t_res_fdblocks_delta += delta;
        if (xfs_sb_version_haslazysbcount(&mp->m_sb))
            flags &= ~XFS_TRANS_SB_DIRTY;
        break;
    case XFS_TRANS_SB_FREXTENTS:
        /*
         * Track the number of blocks allocated in the
         * transaction.  Make sure it does not exceed the
         * number reserved.
         */
        if (delta < 0) {
            tp->t_rtx_res_used += (uint)-delta;
            ASSERT(tp->t_rtx_res_used <= tp->t_rtx_res);
        }
        tp->t_frextents_delta += delta;
        break;
    case XFS_TRANS_SB_RES_FREXTENTS:
        /*
         * The allocation has already been applied to the
         * in-core superblock's counter.  This should only
         * be applied to the on-disk superblock.
         */
        ASSERT(delta < 0);
        tp->t_res_frextents_delta += delta;
        break;
    case XFS_TRANS_SB_DBLOCKS:
        ASSERT(delta > 0);
        tp->t_dblocks_delta += delta;
        break;
    case XFS_TRANS_SB_AGCOUNT:
        ASSERT(delta > 0);
        tp->t_agcount_delta += delta;
        break;
    case XFS_TRANS_SB_IMAXPCT:
        tp->t_imaxpct_delta += delta;
        break;
    case XFS_TRANS_SB_REXTSIZE:
        tp->t_rextsize_delta += delta;
        break;
    case XFS_TRANS_SB_RBMBLOCKS:
        tp->t_rbmblocks_delta += delta;
        break;
    case XFS_TRANS_SB_RBLOCKS:
        tp->t_rblocks_delta += delta;
        break;
    case XFS_TRANS_SB_REXTENTS:
        tp->t_rextents_delta += delta;
        break;
    case XFS_TRANS_SB_REXTSLOG:
        tp->t_rextslog_delta += delta;
        break;
    default:
        ASSERT(0);
        return;
    }

    tp->t_flags |= flags;
}

/*
 * xfs_trans_apply_sb_deltas() is called from the commit code
 * to bring the superblock buffer into the current transaction
 * and modify it as requested by earlier calls to xfs_trans_mod_sb().
 *
 * For now we just look at each field allowed to change and change
 * it if necessary.
 */
STATIC void
xfs_trans_apply_sb_deltas(
    xfs_trans_t *tp)
{
    xfs_dsb_t   *sbp;
    xfs_buf_t   *bp;
    int     whole = 0;

    bp = xfs_trans_getsb(tp, tp->t_mountp, 0);
    sbp = XFS_BUF_TO_SBP(bp);

    /*
     * Check that superblock mods match the mods made to AGF counters.
     */
    ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
           (tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
        tp->t_ag_btree_delta));

    /*
     * Only update the superblock counters if we are logging them
     */
    if (!xfs_sb_version_haslazysbcount(&(tp->t_mountp->m_sb))) {
        if (tp->t_icount_delta)
            be64_add_cpu(&sbp->sb_icount, tp->t_icount_delta);
        if (tp->t_ifree_delta)
            be64_add_cpu(&sbp->sb_ifree, tp->t_ifree_delta);
        if (tp->t_fdblocks_delta)
            be64_add_cpu(&sbp->sb_fdblocks, tp->t_fdblocks_delta);
        if (tp->t_res_fdblocks_delta)
            be64_add_cpu(&sbp->sb_fdblocks, tp->t_res_fdblocks_delta);
    }

    if (tp->t_frextents_delta)
        be64_add_cpu(&sbp->sb_frextents, tp->t_frextents_delta);
    if (tp->t_res_frextents_delta)
        be64_add_cpu(&sbp->sb_frextents, tp->t_res_frextents_delta);

    if (tp->t_dblocks_delta) {
        be64_add_cpu(&sbp->sb_dblocks, tp->t_dblocks_delta);
        whole = 1;
    }
    if (tp->t_agcount_delta) {
        be32_add_cpu(&sbp->sb_agcount, tp->t_agcount_delta);
        whole = 1;
    }
    if (tp->t_imaxpct_delta) {
        sbp->sb_imax_pct += tp->t_imaxpct_delta;
        whole = 1;
    }
    if (tp->t_rextsize_delta) {
        be32_add_cpu(&sbp->sb_rextsize, tp->t_rextsize_delta);
        whole = 1;
    }
    if (tp->t_rbmblocks_delta) {
        be32_add_cpu(&sbp->sb_rbmblocks, tp->t_rbmblocks_delta);
        whole = 1;
    }
    if (tp->t_rblocks_delta) {
        be64_add_cpu(&sbp->sb_rblocks, tp->t_rblocks_delta);
        whole = 1;
    }
    if (tp->t_rextents_delta) {
        be64_add_cpu(&sbp->sb_rextents, tp->t_rextents_delta);
        whole = 1;
    }
    if (tp->t_rextslog_delta) {
        sbp->sb_rextslog += tp->t_rextslog_delta;
        whole = 1;
    }

    if (whole)
        /*
         * Log the whole thing, the fields are noncontiguous.
         */
        xfs_trans_log_buf(tp, bp, 0, sizeof(xfs_dsb_t) - 1);
    else
        /*
         * Since all the modifiable fields are contiguous, we
         * can get away with this.
         */
        xfs_trans_log_buf(tp, bp, offsetof(xfs_dsb_t, sb_icount),
                  offsetof(xfs_dsb_t, sb_frextents) +
                  sizeof(sbp->sb_frextents) - 1);
}

/*
 * xfs_trans_unreserve_and_mod_sb() is called to release unused reservations
 * and apply superblock counter changes to the in-core superblock.  The
 * t_res_fdblocks_delta and t_res_frextents_delta fields are explicitly NOT
 * applied to the in-core superblock.  The idea is that that has already been
 * done.
 *
 * This is done efficiently with a single call to xfs_mod_incore_sb_batch().
 * However, we have to ensure that we only modify each superblock field only
 * once because the application of the delta values may not be atomic. That can
 * lead to ENOSPC races occurring if we have two separate modifcations of the
 * free space counter to put back the entire reservation and then take away
 * what we used.
 *
 * If we are not logging superblock counters, then the inode allocated/free and
 * used block counts are not updated in the on disk superblock. In this case,
 * XFS_TRANS_SB_DIRTY will not be set when the transaction is updated but we
 * still need to update the incore superblock with the changes.
 */
void
xfs_trans_unreserve_and_mod_sb(
    xfs_trans_t *tp)
{
    xfs_mod_sb_t    msb[9]; /* If you add cases, add entries */
    xfs_mod_sb_t    *msbp;
    xfs_mount_t *mp = tp->t_mountp;
    /* REFERENCED */
    int     error;
    int     rsvd;
    int64_t     blkdelta = 0;
    int64_t     rtxdelta = 0;
    int64_t     idelta = 0;
    int64_t     ifreedelta = 0;

    msbp = msb;
    rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;

    /* calculate deltas */
    if (tp->t_blk_res > 0)
        blkdelta = tp->t_blk_res;
    if ((tp->t_fdblocks_delta != 0) &&
        (xfs_sb_version_haslazysbcount(&mp->m_sb) ||
         (tp->t_flags & XFS_TRANS_SB_DIRTY)))
            blkdelta += tp->t_fdblocks_delta;

    if (tp->t_rtx_res > 0)
        rtxdelta = tp->t_rtx_res;
    if ((tp->t_frextents_delta != 0) &&
        (tp->t_flags & XFS_TRANS_SB_DIRTY))
        rtxdelta += tp->t_frextents_delta;

    if (xfs_sb_version_haslazysbcount(&mp->m_sb) ||
         (tp->t_flags & XFS_TRANS_SB_DIRTY)) {
        idelta = tp->t_icount_delta;
        ifreedelta = tp->t_ifree_delta;
    }

    /* apply the per-cpu counters */
    if (blkdelta) {
        error = xfs_icsb_modify_counters(mp, XFS_SBS_FDBLOCKS,
                         blkdelta, rsvd);
        if (error)
            goto out;
    }

    if (idelta) {
        error = xfs_icsb_modify_counters(mp, XFS_SBS_ICOUNT,
                         idelta, rsvd);
        if (error)
            goto out_undo_fdblocks;
    }

    if (ifreedelta) {
        error = xfs_icsb_modify_counters(mp, XFS_SBS_IFREE,
                         ifreedelta, rsvd);
        if (error)
            goto out_undo_icount;
    }

    /* apply remaining deltas */
    if (rtxdelta != 0) {
        msbp->msb_field = XFS_SBS_FREXTENTS;
        msbp->msb_delta = rtxdelta;
        msbp++;
    }

    if (tp->t_flags & XFS_TRANS_SB_DIRTY) {
        if (tp->t_dblocks_delta != 0) {
            msbp->msb_field = XFS_SBS_DBLOCKS;
            msbp->msb_delta = tp->t_dblocks_delta;
            msbp++;
        }
        if (tp->t_agcount_delta != 0) {
            msbp->msb_field = XFS_SBS_AGCOUNT;
            msbp->msb_delta = tp->t_agcount_delta;
            msbp++;
        }
        if (tp->t_imaxpct_delta != 0) {
            msbp->msb_field = XFS_SBS_IMAX_PCT;
            msbp->msb_delta = tp->t_imaxpct_delta;
            msbp++;
        }
        if (tp->t_rextsize_delta != 0) {
            msbp->msb_field = XFS_SBS_REXTSIZE;
            msbp->msb_delta = tp->t_rextsize_delta;
            msbp++;
        }
        if (tp->t_rbmblocks_delta != 0) {
            msbp->msb_field = XFS_SBS_RBMBLOCKS;
            msbp->msb_delta = tp->t_rbmblocks_delta;
            msbp++;
        }
        if (tp->t_rblocks_delta != 0) {
            msbp->msb_field = XFS_SBS_RBLOCKS;
            msbp->msb_delta = tp->t_rblocks_delta;
            msbp++;
        }
        if (tp->t_rextents_delta != 0) {
            msbp->msb_field = XFS_SBS_REXTENTS;
            msbp->msb_delta = tp->t_rextents_delta;
            msbp++;
        }
        if (tp->t_rextslog_delta != 0) {
            msbp->msb_field = XFS_SBS_REXTSLOG;
            msbp->msb_delta = tp->t_rextslog_delta;
            msbp++;
        }
    }

    /*
     * If we need to change anything, do it.
     */
    if (msbp > msb) {
        error = xfs_mod_incore_sb_batch(tp->t_mountp, msb,
            (uint)(msbp - msb), rsvd);
        if (error)
            goto out_undo_ifreecount;
    }

    return;

out_undo_ifreecount:
    if (ifreedelta)
        xfs_icsb_modify_counters(mp, XFS_SBS_IFREE, -ifreedelta, rsvd);
out_undo_icount:
    if (idelta)
        xfs_icsb_modify_counters(mp, XFS_SBS_ICOUNT, -idelta, rsvd);
out_undo_fdblocks:
    if (blkdelta)
        xfs_icsb_modify_counters(mp, XFS_SBS_FDBLOCKS, -blkdelta, rsvd);
out:
    ASSERT(error == 0);
    return;
}

/*
 * Add the given log item to the transaction's list of log items.
 *
 * The log item will now point to its new descriptor with its li_desc field.
 */
void
xfs_trans_add_item(
    struct xfs_trans    *tp,
    struct xfs_log_item *lip)
{
    struct xfs_log_item_desc *lidp;

    ASSERT(lip->li_mountp == tp->t_mountp);
    ASSERT(lip->li_ailp == tp->t_mountp->m_ail);

    lidp = kmem_zone_zalloc(xfs_log_item_desc_zone, KM_SLEEP | KM_NOFS);

    lidp->lid_item = lip;
    lidp->lid_flags = 0;
    list_add_tail(&lidp->lid_trans, &tp->t_items);

    lip->li_desc = lidp;
}

STATIC void
xfs_trans_free_item_desc(
    struct xfs_log_item_desc *lidp)
{
    list_del_init(&lidp->lid_trans);
    kmem_zone_free(xfs_log_item_desc_zone, lidp);
}

/*
 * Unlink and free the given descriptor.
 */
void
xfs_trans_del_item(
    struct xfs_log_item *lip)
{
    xfs_trans_free_item_desc(lip->li_desc);
    lip->li_desc = NULL;
}

/*
 * Unlock all of the items of a transaction and free all the descriptors
 * of that transaction.
 */
void
xfs_trans_free_items(
    struct xfs_trans    *tp,
    xfs_lsn_t       commit_lsn,
    int         flags)
{
    struct xfs_log_item_desc *lidp, *next;

    list_for_each_entry_safe(lidp, next, &tp->t_items, lid_trans) {
        struct xfs_log_item *lip = lidp->lid_item;

        lip->li_desc = NULL;

        if (commit_lsn != NULLCOMMITLSN)
            IOP_COMMITTING(lip, commit_lsn);
        if (flags & XFS_TRANS_ABORT)
            lip->li_flags |= XFS_LI_ABORTED;
        IOP_UNLOCK(lip);

        xfs_trans_free_item_desc(lidp);
    }
}

static inline void
xfs_log_item_batch_insert(
    struct xfs_ail      *ailp,
    struct xfs_ail_cursor   *cur,
    struct xfs_log_item **log_items,
    int         nr_items,
    xfs_lsn_t       commit_lsn)
{
    int i;

    spin_lock(&ailp->xa_lock);
    /* xfs_trans_ail_update_bulk drops ailp->xa_lock */
    xfs_trans_ail_update_bulk(ailp, cur, log_items, nr_items, commit_lsn);

    for (i = 0; i < nr_items; i++)
        IOP_UNPIN(log_items[i], 0);
}

/*
 * Bulk operation version of xfs_trans_committed that takes a log vector of
 * items to insert into the AIL. This uses bulk AIL insertion techniques to
 * minimise lock traffic.
 *
 * If we are called with the aborted flag set, it is because a log write during
 * a CIL checkpoint commit has failed. In this case, all the items in the
 * checkpoint have already gone through IOP_COMMITED and IOP_UNLOCK, which
 * means that checkpoint commit abort handling is treated exactly the same
 * as an iclog write error even though we haven't started any IO yet. Hence in
 * this case all we need to do is IOP_COMMITTED processing, followed by an
 * IOP_UNPIN(aborted) call.
 *
 * The AIL cursor is used to optimise the insert process. If commit_lsn is not
 * at the end of the AIL, the insert cursor avoids the need to walk
 * the AIL to find the insertion point on every xfs_log_item_batch_insert()
 * call. This saves a lot of needless list walking and is a net win, even
 * though it slightly increases that amount of AIL lock traffic to set it up
 * and tear it down.
 */
void
xfs_trans_committed_bulk(
    struct xfs_ail      *ailp,
    struct xfs_log_vec  *log_vector,
    xfs_lsn_t       commit_lsn,
    int         aborted)
{
#define LOG_ITEM_BATCH_SIZE 32
    struct xfs_log_item *log_items[LOG_ITEM_BATCH_SIZE];
    struct xfs_log_vec  *lv;
    struct xfs_ail_cursor   cur;
    int         i = 0;

    spin_lock(&ailp->xa_lock);
    xfs_trans_ail_cursor_last(ailp, &cur, commit_lsn);
    spin_unlock(&ailp->xa_lock);

    /* unpin all the log items */
    for (lv = log_vector; lv; lv = lv->lv_next ) {
        struct xfs_log_item *lip = lv->lv_item;
        xfs_lsn_t       item_lsn;

        if (aborted)
            lip->li_flags |= XFS_LI_ABORTED;
        item_lsn = IOP_COMMITTED(lip, commit_lsn);

        /* item_lsn of -1 means the item needs no further processing */
        if (XFS_LSN_CMP(item_lsn, (xfs_lsn_t)-1) == 0)
            continue;

        /*
         * if we are aborting the operation, no point in inserting the
         * object into the AIL as we are in a shutdown situation.
         */
        if (aborted) {
            ASSERT(XFS_FORCED_SHUTDOWN(ailp->xa_mount));
            IOP_UNPIN(lip, 1);
            continue;
        }

        if (item_lsn != commit_lsn) {

            /*
             * Not a bulk update option due to unusual item_lsn.
             * Push into AIL immediately, rechecking the lsn once
             * we have the ail lock. Then unpin the item. This does
             * not affect the AIL cursor the bulk insert path is
             * using.
             */
            spin_lock(&ailp->xa_lock);
            if (XFS_LSN_CMP(item_lsn, lip->li_lsn) > 0)
                xfs_trans_ail_update(ailp, lip, item_lsn);
            else
                spin_unlock(&ailp->xa_lock);
            IOP_UNPIN(lip, 0);
            continue;
        }

        /* Item is a candidate for bulk AIL insert.  */
        log_items[i++] = lv->lv_item;
        if (i >= LOG_ITEM_BATCH_SIZE) {
            xfs_log_item_batch_insert(ailp, &cur, log_items,
                    LOG_ITEM_BATCH_SIZE, commit_lsn);
            i = 0;
        }
    }

    /* make sure we insert the remainder! */
    if (i)
        xfs_log_item_batch_insert(ailp, &cur, log_items, i, commit_lsn);

    spin_lock(&ailp->xa_lock);
    xfs_trans_ail_cursor_done(ailp, &cur);
    spin_unlock(&ailp->xa_lock);
}

/*
 * Commit the given transaction to the log.
 *
 * XFS disk error handling mechanism is not based on a typical
 * transaction abort mechanism. Logically after the filesystem
 * gets marked 'SHUTDOWN', we can't let any new transactions
 * be durable - ie. committed to disk - because some metadata might
 * be inconsistent. In such cases, this returns an error, and the
 * caller may assume that all locked objects joined to the transaction
 * have already been unlocked as if the commit had succeeded.
 * Do not reference the transaction structure after this call.
 */
int
xfs_trans_commit(
    struct xfs_trans    *tp,
    uint            flags)
{
    struct xfs_mount    *mp = tp->t_mountp;
    xfs_lsn_t       commit_lsn = -1;
    int         error = 0;
    int         log_flags = 0;
    int         sync = tp->t_flags & XFS_TRANS_SYNC;

    /*
     * Determine whether this commit is releasing a permanent
     * log reservation or not.
     */
    if (flags & XFS_TRANS_RELEASE_LOG_RES) {
        ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
        log_flags = XFS_LOG_REL_PERM_RESERV;
    }

    /*
     * If there is nothing to be logged by the transaction,
     * then unlock all of the items associated with the
     * transaction and free the transaction structure.
     * Also make sure to return any reserved blocks to
     * the free pool.
     */
    if (!(tp->t_flags & XFS_TRANS_DIRTY))
        goto out_unreserve;

    if (XFS_FORCED_SHUTDOWN(mp)) {
        error = XFS_ERROR(EIO);
        goto out_unreserve;
    }

    ASSERT(tp->t_ticket != NULL);

    /*
     * If we need to update the superblock, then do it now.
     */
    if (tp->t_flags & XFS_TRANS_SB_DIRTY)
        xfs_trans_apply_sb_deltas(tp);
    xfs_trans_apply_dquot_deltas(tp);

    error = xfs_log_commit_cil(mp, tp, &commit_lsn, flags);
    if (error == ENOMEM) {
        xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
        error = XFS_ERROR(EIO);
        goto out_unreserve;
    }

    current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
    xfs_trans_free(tp);

    /*
     * If the transaction needs to be synchronous, then force the
     * log out now and wait for it.
     */
    if (sync) {
        if (!error) {
            error = _xfs_log_force_lsn(mp, commit_lsn,
                      XFS_LOG_SYNC, NULL);
        }
        XFS_STATS_INC(xs_trans_sync);
    } else {
        XFS_STATS_INC(xs_trans_async);
    }

    return error;

out_unreserve:
    xfs_trans_unreserve_and_mod_sb(tp);

    /*
     * It is indeed possible for the transaction to be not dirty but
     * the dqinfo portion to be.  All that means is that we have some
     * (non-persistent) quota reservations that need to be unreserved.
     */
    xfs_trans_unreserve_and_mod_dquots(tp);
    if (tp->t_ticket) {
        commit_lsn = xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
        if (commit_lsn == -1 && !error)
            error = XFS_ERROR(EIO);
    }
    current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
    xfs_trans_free_items(tp, NULLCOMMITLSN, error ? XFS_TRANS_ABORT : 0);
    xfs_trans_free(tp);

    XFS_STATS_INC(xs_trans_empty);
    return error;
}

/*
 * Unlock all of the transaction's items and free the transaction.
 * The transaction must not have modified any of its items, because
 * there is no way to restore them to their previous state.
 *
 * If the transaction has made a log reservation, make sure to release
 * it as well.
 */
void
xfs_trans_cancel(
    xfs_trans_t     *tp,
    int         flags)
{
    int         log_flags;
    xfs_mount_t     *mp = tp->t_mountp;

    /*
     * See if the caller is being too lazy to figure out if
     * the transaction really needs an abort.
     */
    if ((flags & XFS_TRANS_ABORT) && !(tp->t_flags & XFS_TRANS_DIRTY))
        flags &= ~XFS_TRANS_ABORT;
    /*
     * See if the caller is relying on us to shut down the
     * filesystem.  This happens in paths where we detect
     * corruption and decide to give up.
     */
    if ((tp->t_flags & XFS_TRANS_DIRTY) && !XFS_FORCED_SHUTDOWN(mp)) {
        XFS_ERROR_REPORT("xfs_trans_cancel", XFS_ERRLEVEL_LOW, mp);
        xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
    }
#ifdef DEBUG
    if (!(flags & XFS_TRANS_ABORT) && !XFS_FORCED_SHUTDOWN(mp)) {
        struct xfs_log_item_desc *lidp;

        list_for_each_entry(lidp, &tp->t_items, lid_trans)
            ASSERT(!(lidp->lid_item->li_type == XFS_LI_EFD));
    }
#endif
    xfs_trans_unreserve_and_mod_sb(tp);
    xfs_trans_unreserve_and_mod_dquots(tp);

    if (tp->t_ticket) {
        if (flags & XFS_TRANS_RELEASE_LOG_RES) {
            ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
            log_flags = XFS_LOG_REL_PERM_RESERV;
        } else {
            log_flags = 0;
        }
        xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
    }

    /* mark this thread as no longer being in a transaction */
    current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);

    xfs_trans_free_items(tp, NULLCOMMITLSN, flags);
    xfs_trans_free(tp);
}

/*
 * Roll from one trans in the sequence of PERMANENT transactions to
 * the next: permanent transactions are only flushed out when
 * committed with XFS_TRANS_RELEASE_LOG_RES, but we still want as soon
 * as possible to let chunks of it go to the log. So we commit the
 * chunk we've been working on and get a new transaction to continue.
 */
int
xfs_trans_roll(
    struct xfs_trans    **tpp,
    struct xfs_inode    *dp)
{
    struct xfs_trans    *trans;
    unsigned int        logres, count;
    int         error;

    /*
     * Ensure that the inode is always logged.
     */
    trans = *tpp;
    xfs_trans_log_inode(trans, dp, XFS_ILOG_CORE);

    /*
     * Copy the critical parameters from one trans to the next.
     */
    logres = trans->t_log_res;
    count = trans->t_log_count;
    *tpp = xfs_trans_dup(trans);

    /*
     * Commit the current transaction.
     * If this commit failed, then it'd just unlock those items that
     * are not marked ihold. That also means that a filesystem shutdown
     * is in progress. The caller takes the responsibility to cancel
     * the duplicate transaction that gets returned.
     */
    error = xfs_trans_commit(trans, 0);
    if (error)
        return (error);

    trans = *tpp;

    /*
     * transaction commit worked ok so we can drop the extra ticket
     * reference that we gained in xfs_trans_dup()
     */
    xfs_log_ticket_put(trans->t_ticket);


    /*
     * Reserve space in the log for th next transaction.
     * This also pushes items in the "AIL", the list of logged items,
     * out to disk if they are taking up space at the tail of the log
     * that we want to use.  This requires that either nothing be locked
     * across this call, or that anything that is locked be logged in
     * the prior and the next transactions.
     */
    error = xfs_trans_reserve(trans, 0, logres, 0,
                  XFS_TRANS_PERM_LOG_RES, count);
    /*
     *  Ensure that the inode is in the new transaction and locked.
     */
    if (error)
        return error;

    xfs_trans_ijoin(trans, dp, 0);
    return 0;
}