MIPS: Yosemite, Emma: Fix off-by-two in arcs_cmdline buffer size check

[linux-2.6/linux-mips.git] / fs / xfs / xfs_trans.c

/*
 * 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_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_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_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_wait_for_freeze(mp, SB_FREEZE_TRANS);
        return _xfs_trans_alloc(mp, type, KM_SLEEP);
}

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

        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_alloc_busy_sort(&tp->t_busy);
        xfs_alloc_busy_clear(tp->t_mountp, &tp->t_busy, false);

        atomic_dec(&tp->t_mountp->m_active_trans);
        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);
        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             log_flags;
        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) {
                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) {
                        log_flags = XFS_LOG_PERM_RESERV;
                        tp->t_flags |= XFS_TRANS_PERM_LOG_RES;
                } else {
                        ASSERT(tp->t_ticket == NULL);
                        ASSERT(!(tp->t_flags & XFS_TRANS_PERM_LOG_RES));
                        log_flags = 0;
                }

                error = xfs_log_reserve(tp->t_mountp, logspace, logcount,
                                        &tp->t_ticket,
                                        XFS_TRANSACTION, log_flags, 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) {
                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;
        lidp->lid_size = 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);
        }
}

/*
 * Unlock the items associated with a transaction.
 *
 * Items which were not logged should be freed.  Those which were logged must
 * still be tracked so they can be unpinned when the transaction commits.
 */
STATIC void
xfs_trans_unlock_items(
        struct xfs_trans        *tp,
        xfs_lsn_t               commit_lsn)
{
        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);
                IOP_UNLOCK(lip);

                /*
                 * Free the descriptor if the item is not dirty
                 * within this transaction.
                 */
                if (!(lidp->lid_flags & XFS_LID_DIRTY))
                        xfs_trans_free_item_desc(lidp);
        }
}

/*
 * Total up the number of log iovecs needed to commit this
 * transaction.  The transaction itself needs one for the
 * transaction header.  Ask each dirty item in turn how many
 * it needs to get the total.
 */
static uint
xfs_trans_count_vecs(
        struct xfs_trans        *tp)
{
        int                     nvecs;
        struct xfs_log_item_desc *lidp;

        nvecs = 1;

        /* In the non-debug case we need to start bailing out if we
         * didn't find a log_item here, return zero and let trans_commit
         * deal with it.
         */
        if (list_empty(&tp->t_items)) {
                ASSERT(0);
                return 0;
        }

        list_for_each_entry(lidp, &tp->t_items, lid_trans) {
                /*
                 * Skip items which aren't dirty in this transaction.
                 */
                if (!(lidp->lid_flags & XFS_LID_DIRTY))
                        continue;
                lidp->lid_size = IOP_SIZE(lidp->lid_item);
                nvecs += lidp->lid_size;
        }

        return nvecs;
}

/*
 * Fill in the vector with pointers to data to be logged
 * by this transaction.  The transaction header takes
 * the first vector, and then each dirty item takes the
 * number of vectors it indicated it needed in xfs_trans_count_vecs().
 *
 * As each item fills in the entries it needs, also pin the item
 * so that it cannot be flushed out until the log write completes.
 */
static void
xfs_trans_fill_vecs(
        struct xfs_trans        *tp,
        struct xfs_log_iovec    *log_vector)
{
        struct xfs_log_item_desc *lidp;
        struct xfs_log_iovec    *vecp;
        uint                    nitems;

        /*
         * Skip over the entry for the transaction header, we'll
         * fill that in at the end.
         */
        vecp = log_vector + 1;

        nitems = 0;
        ASSERT(!list_empty(&tp->t_items));
        list_for_each_entry(lidp, &tp->t_items, lid_trans) {
                /* Skip items which aren't dirty in this transaction. */
                if (!(lidp->lid_flags & XFS_LID_DIRTY))
                        continue;

                /*
                 * The item may be marked dirty but not log anything.  This can
                 * be used to get called when a transaction is committed.
                 */
                if (lidp->lid_size)
                        nitems++;
                IOP_FORMAT(lidp->lid_item, vecp);
                vecp += lidp->lid_size;
                IOP_PIN(lidp->lid_item);
        }

        /*
         * Now that we've counted the number of items in this transaction, fill
         * in the transaction header. Note that the transaction header does not
         * have a log item.
         */
        tp->t_header.th_magic = XFS_TRANS_HEADER_MAGIC;
        tp->t_header.th_type = tp->t_type;
        tp->t_header.th_num_items = nitems;
        log_vector->i_addr = (xfs_caddr_t)&tp->t_header;
        log_vector->i_len = sizeof(xfs_trans_header_t);
        log_vector->i_type = XLOG_REG_TYPE_TRANSHDR;
}

/*
 * The committed item processing consists of calling the committed routine of
 * each logged item, updating the item's position in the AIL if necessary, and
 * unpinning each item.  If the committed routine returns -1, then do nothing
 * further with the item because it may have been freed.
 *
 * Since items are unlocked when they are copied to the incore log, it is
 * possible for two transactions to be completing and manipulating the same
 * item simultaneously.  The AIL lock will protect the lsn field of each item.
 * The value of this field can never go backwards.
 *
 * We unpin the items after repositioning them in the AIL, because otherwise
 * they could be immediately flushed and we'd have to race with the flusher
 * trying to pull the item from the AIL as we add it.
 */
static void
xfs_trans_item_committed(
        struct xfs_log_item     *lip,
        xfs_lsn_t               commit_lsn,
        int                     aborted)
{
        xfs_lsn_t               item_lsn;
        struct xfs_ail          *ailp;

        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)
                return;

        /*
         * If the returned lsn is greater than what it contained before, update
         * the location of the item in the AIL.  If it is not, then do nothing.
         * Items can never move backwards in the AIL.
         *
         * While the new lsn should usually be greater, it is possible that a
         * later transaction completing simultaneously with an earlier one
         * using the same item could complete first with a higher lsn.  This
         * would cause the earlier transaction to fail the test below.
         */
        ailp = lip->li_ailp;
        spin_lock(&ailp->xa_lock);
        if (XFS_LSN_CMP(item_lsn, lip->li_lsn) > 0) {
                /*
                 * This will set the item's lsn to item_lsn and update the
                 * position of the item in the AIL.
                 *
                 * xfs_trans_ail_update() drops the AIL lock.
                 */
                xfs_trans_ail_update(ailp, lip, item_lsn);
        } else {
                spin_unlock(&ailp->xa_lock);
        }

        /*
         * Now that we've repositioned the item in the AIL, unpin it so it can
         * be flushed. Pass information about buffer stale state down from the
         * log item flags, if anyone else stales the buffer we do not want to
         * pay any attention to it.
         */
        IOP_UNPIN(lip, 0);
}

/*
 * This is typically called by the LM when a transaction has been fully
 * committed to disk.  It needs to unpin the items which have
 * been logged by the transaction and update their positions
 * in the AIL if necessary.
 *
 * This also gets called when the transactions didn't get written out
 * because of an I/O error. Abortflag & XFS_LI_ABORTED is set then.
 */
STATIC void
xfs_trans_committed(
        void                    *arg,
        int                     abortflag)
{
        struct xfs_trans        *tp = arg;
        struct xfs_log_item_desc *lidp, *next;

        list_for_each_entry_safe(lidp, next, &tp->t_items, lid_trans) {
                xfs_trans_item_committed(lidp->lid_item, tp->t_lsn, abortflag);
                xfs_trans_free_item_desc(lidp);
        }

        xfs_trans_free(tp);
}

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);
}

/*
 * Called from the trans_commit code when we notice that the filesystem is in
 * the middle of a forced shutdown.
 *
 * When we are called here, we have already pinned all the items in the
 * transaction. However, neither IOP_COMMITTING or IOP_UNLOCK has been called
 * so we can simply walk the items in the transaction, unpin them with an abort
 * flag and then free the items. Note that unpinning the items can result in
 * them being freed immediately, so we need to use a safe list traversal method
 * here.
 */
STATIC void
xfs_trans_uncommit(
        struct xfs_trans        *tp,
        uint                    flags)
{
        struct xfs_log_item_desc *lidp, *n;

        list_for_each_entry_safe(lidp, n, &tp->t_items, lid_trans) {
                if (lidp->lid_flags & XFS_LID_DIRTY)
                        IOP_UNPIN(lidp->lid_item, 1);
        }

        xfs_trans_unreserve_and_mod_sb(tp);
        xfs_trans_unreserve_and_mod_dquots(tp);

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

/*
 * Format the transaction direct to the iclog. This isolates the physical
 * transaction commit operation from the logical operation and hence allows
 * other methods to be introduced without affecting the existing commit path.
 */
static int
xfs_trans_commit_iclog(
        struct xfs_mount        *mp,
        struct xfs_trans        *tp,
        xfs_lsn_t               *commit_lsn,
        int                     flags)
{
        int                     shutdown;
        int                     error;
        int                     log_flags = 0;
        struct xlog_in_core     *commit_iclog;
#define XFS_TRANS_LOGVEC_COUNT  16
        struct xfs_log_iovec    log_vector_fast[XFS_TRANS_LOGVEC_COUNT];
        struct xfs_log_iovec    *log_vector;
        uint                    nvec;


        /*
         * Ask each log item how many log_vector entries it will
         * need so we can figure out how many to allocate.
         * Try to avoid the kmem_alloc() call in the common case
         * by using a vector from the stack when it fits.
         */
        nvec = xfs_trans_count_vecs(tp);
        if (nvec == 0) {
                return ENOMEM;  /* triggers a shutdown! */
        } else if (nvec <= XFS_TRANS_LOGVEC_COUNT) {
                log_vector = log_vector_fast;
        } else {
                log_vector = (xfs_log_iovec_t *)kmem_alloc(nvec *
                                                   sizeof(xfs_log_iovec_t),
                                                   KM_SLEEP);
        }

        /*
         * Fill in the log_vector and pin the logged items, and
         * then write the transaction to the log.
         */
        xfs_trans_fill_vecs(tp, log_vector);

        if (flags & XFS_TRANS_RELEASE_LOG_RES)
                log_flags = XFS_LOG_REL_PERM_RESERV;

        error = xfs_log_write(mp, log_vector, nvec, tp->t_ticket, &(tp->t_lsn));

        /*
         * The transaction is committed incore here, and can go out to disk
         * at any time after this call.  However, all the items associated
         * with the transaction are still locked and pinned in memory.
         */
        *commit_lsn = xfs_log_done(mp, tp->t_ticket, &commit_iclog, log_flags);

        tp->t_commit_lsn = *commit_lsn;
        trace_xfs_trans_commit_lsn(tp);

        if (nvec > XFS_TRANS_LOGVEC_COUNT)
                kmem_free(log_vector);

        /*
         * If we got a log write error. Unpin the logitems that we
         * had pinned, clean up, free trans structure, and return error.
         */
        if (error || *commit_lsn == -1) {
                current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
                xfs_trans_uncommit(tp, flags|XFS_TRANS_ABORT);
                return XFS_ERROR(EIO);
        }

        /*
         * Once the transaction has committed, unused
         * reservations need to be released and changes to
         * the superblock need to be reflected in the in-core
         * version.  Do that now.
         */
        xfs_trans_unreserve_and_mod_sb(tp);

        /*
         * Tell the LM to call the transaction completion routine
         * when the log write with LSN commit_lsn completes (e.g.
         * when the transaction commit really hits the on-disk log).
         * After this call we cannot reference tp, because the call
         * can happen at any time and the call will free the transaction
         * structure pointed to by tp.  The only case where we call
         * the completion routine (xfs_trans_committed) directly is
         * if the log is turned off on a debug kernel or we're
         * running in simulation mode (the log is explicitly turned
         * off).
         */
        tp->t_logcb.cb_func = xfs_trans_committed;
        tp->t_logcb.cb_arg = tp;

        /*
         * We need to pass the iclog buffer which was used for the
         * transaction commit record into this function, and attach
         * the callback to it. The callback must be attached before
         * the items are unlocked to avoid racing with other threads
         * waiting for an item to unlock.
         */
        shutdown = xfs_log_notify(mp, commit_iclog, &(tp->t_logcb));

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

        /*
         * Once all the items of the transaction have been copied
         * to the in core log and the callback is attached, the
         * items can be unlocked.
         *
         * This will free descriptors pointing to items which were
         * not logged since there is nothing more to do with them.
         * For items which were logged, we will keep pointers to them
         * so they can be unpinned after the transaction commits to disk.
         * This will also stamp each modified meta-data item with
         * the commit lsn of this transaction for dependency tracking
         * purposes.
         */
        xfs_trans_unlock_items(tp, *commit_lsn);

        /*
         * If we detected a log error earlier, finish committing
         * the transaction now (unpin log items, etc).
         *
         * Order is critical here, to avoid using the transaction
         * pointer after its been freed (by xfs_trans_committed
         * either here now, or as a callback).  We cannot do this
         * step inside xfs_log_notify as was done earlier because
         * of this issue.
         */
        if (shutdown)
                xfs_trans_committed(tp, XFS_LI_ABORTED);

        /*
         * Now that the xfs_trans_committed callback has been attached,
         * and the items are released we can finally allow the iclog to
         * go to disk.
         */
        return xfs_log_release_iclog(mp, commit_iclog);
}

/*
 * Walk the log items and allocate log vector structures for
 * each item large enough to fit all the vectors they require.
 * Note that this format differs from the old log vector format in
 * that there is no transaction header in these log vectors.
 */
STATIC struct xfs_log_vec *
xfs_trans_alloc_log_vecs(
        xfs_trans_t     *tp)
{
        struct xfs_log_item_desc *lidp;
        struct xfs_log_vec      *lv = NULL;
        struct xfs_log_vec      *ret_lv = NULL;


        /* Bail out if we didn't find a log item.  */
        if (list_empty(&tp->t_items)) {
                ASSERT(0);
                return NULL;
        }

        list_for_each_entry(lidp, &tp->t_items, lid_trans) {
                struct xfs_log_vec *new_lv;

                /* Skip items which aren't dirty in this transaction. */
                if (!(lidp->lid_flags & XFS_LID_DIRTY))
                        continue;

                /* Skip items that do not have any vectors for writing */
                lidp->lid_size = IOP_SIZE(lidp->lid_item);
                if (!lidp->lid_size)
                        continue;

                new_lv = kmem_zalloc(sizeof(*new_lv) +
                                lidp->lid_size * sizeof(struct xfs_log_iovec),
                                KM_SLEEP);

                /* The allocated iovec region lies beyond the log vector. */
                new_lv->lv_iovecp = (struct xfs_log_iovec *)&new_lv[1];
                new_lv->lv_niovecs = lidp->lid_size;
                new_lv->lv_item = lidp->lid_item;
                if (!ret_lv)
                        ret_lv = new_lv;
                else
                        lv->lv_next = new_lv;
                lv = new_lv;
        }

        return ret_lv;
}

static int
xfs_trans_commit_cil(
        struct xfs_mount        *mp,
        struct xfs_trans        *tp,
        xfs_lsn_t               *commit_lsn,
        int                     flags)
{
        struct xfs_log_vec      *log_vector;

        /*
         * Get each log item to allocate a vector structure for
         * the log item to to pass to the log write code. The
         * CIL commit code will format the vector and save it away.
         */
        log_vector = xfs_trans_alloc_log_vecs(tp);
        if (!log_vector)
                return ENOMEM;

        xfs_log_commit_cil(mp, tp, log_vector, commit_lsn, flags);

        current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
        xfs_trans_free(tp);
        return 0;
}

/*
 * 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);

        if (mp->m_flags & XFS_MOUNT_DELAYLOG)
                error = xfs_trans_commit_cil(mp, tp, &commit_lsn, flags);
        else
                error = xfs_trans_commit_iclog(mp, tp, &commit_lsn, flags);

        if (error == ENOMEM) {
                xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
                error = XFS_ERROR(EIO);
                goto out_unreserve;
        }

        /*
         * 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;
}