xfs_mount.c

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/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_rtalloc.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_quota.h"
#include "xfs_fsops.h"
#include "xfs_utils.h"
#include "xfs_trace.h"


#ifdef HAVE_PERCPU_SB
STATIC void xfs_icsb_balance_counter(xfs_mount_t *, xfs_sb_field_t,
                        int);
STATIC void xfs_icsb_balance_counter_locked(xfs_mount_t *, xfs_sb_field_t,
                        int);
STATIC void xfs_icsb_disable_counter(xfs_mount_t *, xfs_sb_field_t);
#else

#define xfs_icsb_balance_counter(mp, a, b)      do { } while (0)
#define xfs_icsb_balance_counter_locked(mp, a, b)   do { } while (0)
#endif

static const struct {
    short offset;
    short type; /* 0 = integer
             * 1 = binary / string (no translation)
             */
} xfs_sb_info[] = {
    { offsetof(xfs_sb_t, sb_magicnum),   0 },
    { offsetof(xfs_sb_t, sb_blocksize),  0 },
    { offsetof(xfs_sb_t, sb_dblocks),    0 },
    { offsetof(xfs_sb_t, sb_rblocks),    0 },
    { offsetof(xfs_sb_t, sb_rextents),   0 },
    { offsetof(xfs_sb_t, sb_uuid),       1 },
    { offsetof(xfs_sb_t, sb_logstart),   0 },
    { offsetof(xfs_sb_t, sb_rootino),    0 },
    { offsetof(xfs_sb_t, sb_rbmino),     0 },
    { offsetof(xfs_sb_t, sb_rsumino),    0 },
    { offsetof(xfs_sb_t, sb_rextsize),   0 },
    { offsetof(xfs_sb_t, sb_agblocks),   0 },
    { offsetof(xfs_sb_t, sb_agcount),    0 },
    { offsetof(xfs_sb_t, sb_rbmblocks),  0 },
    { offsetof(xfs_sb_t, sb_logblocks),  0 },
    { offsetof(xfs_sb_t, sb_versionnum), 0 },
    { offsetof(xfs_sb_t, sb_sectsize),   0 },
    { offsetof(xfs_sb_t, sb_inodesize),  0 },
    { offsetof(xfs_sb_t, sb_inopblock),  0 },
    { offsetof(xfs_sb_t, sb_fname[0]),   1 },
    { offsetof(xfs_sb_t, sb_blocklog),   0 },
    { offsetof(xfs_sb_t, sb_sectlog),    0 },
    { offsetof(xfs_sb_t, sb_inodelog),   0 },
    { offsetof(xfs_sb_t, sb_inopblog),   0 },
    { offsetof(xfs_sb_t, sb_agblklog),   0 },
    { offsetof(xfs_sb_t, sb_rextslog),   0 },
    { offsetof(xfs_sb_t, sb_inprogress), 0 },
    { offsetof(xfs_sb_t, sb_imax_pct),   0 },
    { offsetof(xfs_sb_t, sb_icount),     0 },
    { offsetof(xfs_sb_t, sb_ifree),      0 },
    { offsetof(xfs_sb_t, sb_fdblocks),   0 },
    { offsetof(xfs_sb_t, sb_frextents),  0 },
    { offsetof(xfs_sb_t, sb_uquotino),   0 },
    { offsetof(xfs_sb_t, sb_gquotino),   0 },
    { offsetof(xfs_sb_t, sb_qflags),     0 },
    { offsetof(xfs_sb_t, sb_flags),      0 },
    { offsetof(xfs_sb_t, sb_shared_vn),  0 },
    { offsetof(xfs_sb_t, sb_inoalignmt), 0 },
    { offsetof(xfs_sb_t, sb_unit),   0 },
    { offsetof(xfs_sb_t, sb_width),  0 },
    { offsetof(xfs_sb_t, sb_dirblklog),  0 },
    { offsetof(xfs_sb_t, sb_logsectlog), 0 },
    { offsetof(xfs_sb_t, sb_logsectsize),0 },
    { offsetof(xfs_sb_t, sb_logsunit),   0 },
    { offsetof(xfs_sb_t, sb_features2),  0 },
    { offsetof(xfs_sb_t, sb_bad_features2), 0 },
    { sizeof(xfs_sb_t),          0 }
};

static DEFINE_MUTEX(xfs_uuid_table_mutex);
static int xfs_uuid_table_size;
static uuid_t *xfs_uuid_table;

/*
 * See if the UUID is unique among mounted XFS filesystems.
 * Mount fails if UUID is nil or a FS with the same UUID is already mounted.
 */
STATIC int
xfs_uuid_mount(
    struct xfs_mount    *mp)
{
    uuid_t          *uuid = &mp->m_sb.sb_uuid;
    int         hole, i;

    if (mp->m_flags & XFS_MOUNT_NOUUID)
        return 0;

    if (uuid_is_nil(uuid)) {
        xfs_warn(mp, "Filesystem has nil UUID - can't mount");
        return XFS_ERROR(EINVAL);
    }

    mutex_lock(&xfs_uuid_table_mutex);
    for (i = 0, hole = -1; i < xfs_uuid_table_size; i++) {
        if (uuid_is_nil(&xfs_uuid_table[i])) {
            hole = i;
            continue;
        }
        if (uuid_equal(uuid, &xfs_uuid_table[i]))
            goto out_duplicate;
    }

    if (hole < 0) {
        xfs_uuid_table = kmem_realloc(xfs_uuid_table,
            (xfs_uuid_table_size + 1) * sizeof(*xfs_uuid_table),
            xfs_uuid_table_size  * sizeof(*xfs_uuid_table),
            KM_SLEEP);
        hole = xfs_uuid_table_size++;
    }
    xfs_uuid_table[hole] = *uuid;
    mutex_unlock(&xfs_uuid_table_mutex);

    return 0;

 out_duplicate:
    mutex_unlock(&xfs_uuid_table_mutex);
    xfs_warn(mp, "Filesystem has duplicate UUID %pU - can't mount", uuid);
    return XFS_ERROR(EINVAL);
}

STATIC void
xfs_uuid_unmount(
    struct xfs_mount    *mp)
{
    uuid_t          *uuid = &mp->m_sb.sb_uuid;
    int         i;

    if (mp->m_flags & XFS_MOUNT_NOUUID)
        return;

    mutex_lock(&xfs_uuid_table_mutex);
    for (i = 0; i < xfs_uuid_table_size; i++) {
        if (uuid_is_nil(&xfs_uuid_table[i]))
            continue;
        if (!uuid_equal(uuid, &xfs_uuid_table[i]))
            continue;
        memset(&xfs_uuid_table[i], 0, sizeof(uuid_t));
        break;
    }
    ASSERT(i < xfs_uuid_table_size);
    mutex_unlock(&xfs_uuid_table_mutex);
}


/*
 * Reference counting access wrappers to the perag structures.
 * Because we never free per-ag structures, the only thing we
 * have to protect against changes is the tree structure itself.
 */
struct xfs_perag *
xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
{
    struct xfs_perag    *pag;
    int         ref = 0;

    rcu_read_lock();
    pag = radix_tree_lookup(&mp->m_perag_tree, agno);
    if (pag) {
        ASSERT(atomic_read(&pag->pag_ref) >= 0);
        ref = atomic_inc_return(&pag->pag_ref);
    }
    rcu_read_unlock();
    trace_xfs_perag_get(mp, agno, ref, _RET_IP_);
    return pag;
}

/*
 * search from @first to find the next perag with the given tag set.
 */
struct xfs_perag *
xfs_perag_get_tag(
    struct xfs_mount    *mp,
    xfs_agnumber_t      first,
    int         tag)
{
    struct xfs_perag    *pag;
    int         found;
    int         ref;

    rcu_read_lock();
    found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
                    (void **)&pag, first, 1, tag);
    if (found <= 0) {
        rcu_read_unlock();
        return NULL;
    }
    ref = atomic_inc_return(&pag->pag_ref);
    rcu_read_unlock();
    trace_xfs_perag_get_tag(mp, pag->pag_agno, ref, _RET_IP_);
    return pag;
}

void
xfs_perag_put(struct xfs_perag *pag)
{
    int ref;

    ASSERT(atomic_read(&pag->pag_ref) > 0);
    ref = atomic_dec_return(&pag->pag_ref);
    trace_xfs_perag_put(pag->pag_mount, pag->pag_agno, ref, _RET_IP_);
}

STATIC void
__xfs_free_perag(
    struct rcu_head *head)
{
    struct xfs_perag *pag = container_of(head, struct xfs_perag, rcu_head);

    ASSERT(atomic_read(&pag->pag_ref) == 0);
    kmem_free(pag);
}

/*
 * Free up the per-ag resources associated with the mount structure.
 */
STATIC void
xfs_free_perag(
    xfs_mount_t *mp)
{
    xfs_agnumber_t  agno;
    struct xfs_perag *pag;

    for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
        spin_lock(&mp->m_perag_lock);
        pag = radix_tree_delete(&mp->m_perag_tree, agno);
        spin_unlock(&mp->m_perag_lock);
        ASSERT(pag);
        ASSERT(atomic_read(&pag->pag_ref) == 0);
        call_rcu(&pag->rcu_head, __xfs_free_perag);
    }
}

/*
 * Check size of device based on the (data/realtime) block count.
 * Note: this check is used by the growfs code as well as mount.
 */
int
xfs_sb_validate_fsb_count(
    xfs_sb_t    *sbp,
    __uint64_t  nblocks)
{
    ASSERT(PAGE_SHIFT >= sbp->sb_blocklog);
    ASSERT(sbp->sb_blocklog >= BBSHIFT);

#if XFS_BIG_BLKNOS     /* Limited by ULONG_MAX of page cache index */
    if (nblocks >> (PAGE_CACHE_SHIFT - sbp->sb_blocklog) > ULONG_MAX)
        return EFBIG;
#else                  /* Limited by UINT_MAX of sectors */
    if (nblocks << (sbp->sb_blocklog - BBSHIFT) > UINT_MAX)
        return EFBIG;
#endif
    return 0;
}

/*
 * Check the validity of the SB found.
 */
STATIC int
xfs_mount_validate_sb(
    xfs_mount_t *mp,
    xfs_sb_t    *sbp,
    int     flags)
{
    int     loud = !(flags & XFS_MFSI_QUIET);

    /*
     * If the log device and data device have the
     * same device number, the log is internal.
     * Consequently, the sb_logstart should be non-zero.  If
     * we have a zero sb_logstart in this case, we may be trying to mount
     * a volume filesystem in a non-volume manner.
     */
    if (sbp->sb_magicnum != XFS_SB_MAGIC) {
        if (loud)
            xfs_warn(mp, "bad magic number");
        return XFS_ERROR(EWRONGFS);
    }

    if (!xfs_sb_good_version(sbp)) {
        if (loud)
            xfs_warn(mp, "bad version");
        return XFS_ERROR(EWRONGFS);
    }

    if (unlikely(
        sbp->sb_logstart == 0 && mp->m_logdev_targp == mp->m_ddev_targp)) {
        if (loud)
            xfs_warn(mp,
        "filesystem is marked as having an external log; "
        "specify logdev on the mount command line.");
        return XFS_ERROR(EINVAL);
    }

    if (unlikely(
        sbp->sb_logstart != 0 && mp->m_logdev_targp != mp->m_ddev_targp)) {
        if (loud)
            xfs_warn(mp,
        "filesystem is marked as having an internal log; "
        "do not specify logdev on the mount command line.");
        return XFS_ERROR(EINVAL);
    }

    /*
     * More sanity checking.  Most of these were stolen directly from
     * xfs_repair.
     */
    if (unlikely(
        sbp->sb_agcount <= 0                    ||
        sbp->sb_sectsize < XFS_MIN_SECTORSIZE           ||
        sbp->sb_sectsize > XFS_MAX_SECTORSIZE           ||
        sbp->sb_sectlog < XFS_MIN_SECTORSIZE_LOG            ||
        sbp->sb_sectlog > XFS_MAX_SECTORSIZE_LOG            ||
        sbp->sb_sectsize != (1 << sbp->sb_sectlog)          ||
        sbp->sb_blocksize < XFS_MIN_BLOCKSIZE           ||
        sbp->sb_blocksize > XFS_MAX_BLOCKSIZE           ||
        sbp->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG            ||
        sbp->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG            ||
        sbp->sb_blocksize != (1 << sbp->sb_blocklog)        ||
        sbp->sb_inodesize < XFS_DINODE_MIN_SIZE         ||
        sbp->sb_inodesize > XFS_DINODE_MAX_SIZE         ||
        sbp->sb_inodelog < XFS_DINODE_MIN_LOG           ||
        sbp->sb_inodelog > XFS_DINODE_MAX_LOG           ||
        sbp->sb_inodesize != (1 << sbp->sb_inodelog)        ||
        (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog)   ||
        (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE)  ||
        (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)  ||
        (sbp->sb_imax_pct > 100 /* zero sb_imax_pct is valid */)    ||
        sbp->sb_dblocks == 0                    ||
        sbp->sb_dblocks > XFS_MAX_DBLOCKS(sbp)          ||
        sbp->sb_dblocks < XFS_MIN_DBLOCKS(sbp))) {
        if (loud)
            XFS_CORRUPTION_ERROR("SB sanity check failed",
                XFS_ERRLEVEL_LOW, mp, sbp);
        return XFS_ERROR(EFSCORRUPTED);
    }

    /*
     * Until this is fixed only page-sized or smaller data blocks work.
     */
    if (unlikely(sbp->sb_blocksize > PAGE_SIZE)) {
        if (loud) {
            xfs_warn(mp,
        "File system with blocksize %d bytes. "
        "Only pagesize (%ld) or less will currently work.",
                sbp->sb_blocksize, PAGE_SIZE);
        }
        return XFS_ERROR(ENOSYS);
    }

    /*
     * Currently only very few inode sizes are supported.
     */
    switch (sbp->sb_inodesize) {
    case 256:
    case 512:
    case 1024:
    case 2048:
        break;
    default:
        if (loud)
            xfs_warn(mp, "inode size of %d bytes not supported",
                sbp->sb_inodesize);
        return XFS_ERROR(ENOSYS);
    }

    if (xfs_sb_validate_fsb_count(sbp, sbp->sb_dblocks) ||
        xfs_sb_validate_fsb_count(sbp, sbp->sb_rblocks)) {
        if (loud)
            xfs_warn(mp,
        "file system too large to be mounted on this system.");
        return XFS_ERROR(EFBIG);
    }

    if (unlikely(sbp->sb_inprogress)) {
        if (loud)
            xfs_warn(mp, "file system busy");
        return XFS_ERROR(EFSCORRUPTED);
    }

    /*
     * Version 1 directory format has never worked on Linux.
     */
    if (unlikely(!xfs_sb_version_hasdirv2(sbp))) {
        if (loud)
            xfs_warn(mp,
                "file system using version 1 directory format");
        return XFS_ERROR(ENOSYS);
    }

    return 0;
}

int
xfs_initialize_perag(
    xfs_mount_t *mp,
    xfs_agnumber_t  agcount,
    xfs_agnumber_t  *maxagi)
{
    xfs_agnumber_t  index;
    xfs_agnumber_t  first_initialised = 0;
    xfs_perag_t *pag;
    xfs_agino_t agino;
    xfs_ino_t   ino;
    xfs_sb_t    *sbp = &mp->m_sb;
    int     error = -ENOMEM;

    /*
     * Walk the current per-ag tree so we don't try to initialise AGs
     * that already exist (growfs case). Allocate and insert all the
     * AGs we don't find ready for initialisation.
     */
    for (index = 0; index < agcount; index++) {
        pag = xfs_perag_get(mp, index);
        if (pag) {
            xfs_perag_put(pag);
            continue;
        }
        if (!first_initialised)
            first_initialised = index;

        pag = kmem_zalloc(sizeof(*pag), KM_MAYFAIL);
        if (!pag)
            goto out_unwind;
        pag->pag_agno = index;
        pag->pag_mount = mp;
        spin_lock_init(&pag->pag_ici_lock);
        mutex_init(&pag->pag_ici_reclaim_lock);
        INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
        spin_lock_init(&pag->pag_buf_lock);
        pag->pag_buf_tree = RB_ROOT;

        if (radix_tree_preload(GFP_NOFS))
            goto out_unwind;

        spin_lock(&mp->m_perag_lock);
        if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
            BUG();
            spin_unlock(&mp->m_perag_lock);
            radix_tree_preload_end();
            error = -EEXIST;
            goto out_unwind;
        }
        spin_unlock(&mp->m_perag_lock);
        radix_tree_preload_end();
    }

    /*
     * If we mount with the inode64 option, or no inode overflows
     * the legacy 32-bit address space clear the inode32 option.
     */
    agino = XFS_OFFBNO_TO_AGINO(mp, sbp->sb_agblocks - 1, 0);
    ino = XFS_AGINO_TO_INO(mp, agcount - 1, agino);

    if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) && ino > XFS_MAXINUMBER_32)
        mp->m_flags |= XFS_MOUNT_32BITINODES;
    else
        mp->m_flags &= ~XFS_MOUNT_32BITINODES;

    if (mp->m_flags & XFS_MOUNT_32BITINODES)
        index = xfs_set_inode32(mp);
    else
        index = xfs_set_inode64(mp);

    if (maxagi)
        *maxagi = index;
    return 0;

out_unwind:
    kmem_free(pag);
    for (; index > first_initialised; index--) {
        pag = radix_tree_delete(&mp->m_perag_tree, index);
        kmem_free(pag);
    }
    return error;
}

void
xfs_sb_from_disk(
    struct xfs_mount    *mp,
    xfs_dsb_t   *from)
{
    struct xfs_sb *to = &mp->m_sb;

    to->sb_magicnum = be32_to_cpu(from->sb_magicnum);
    to->sb_blocksize = be32_to_cpu(from->sb_blocksize);
    to->sb_dblocks = be64_to_cpu(from->sb_dblocks);
    to->sb_rblocks = be64_to_cpu(from->sb_rblocks);
    to->sb_rextents = be64_to_cpu(from->sb_rextents);
    memcpy(&to->sb_uuid, &from->sb_uuid, sizeof(to->sb_uuid));
    to->sb_logstart = be64_to_cpu(from->sb_logstart);
    to->sb_rootino = be64_to_cpu(from->sb_rootino);
    to->sb_rbmino = be64_to_cpu(from->sb_rbmino);
    to->sb_rsumino = be64_to_cpu(from->sb_rsumino);
    to->sb_rextsize = be32_to_cpu(from->sb_rextsize);
    to->sb_agblocks = be32_to_cpu(from->sb_agblocks);
    to->sb_agcount = be32_to_cpu(from->sb_agcount);
    to->sb_rbmblocks = be32_to_cpu(from->sb_rbmblocks);
    to->sb_logblocks = be32_to_cpu(from->sb_logblocks);
    to->sb_versionnum = be16_to_cpu(from->sb_versionnum);
    to->sb_sectsize = be16_to_cpu(from->sb_sectsize);
    to->sb_inodesize = be16_to_cpu(from->sb_inodesize);
    to->sb_inopblock = be16_to_cpu(from->sb_inopblock);
    memcpy(&to->sb_fname, &from->sb_fname, sizeof(to->sb_fname));
    to->sb_blocklog = from->sb_blocklog;
    to->sb_sectlog = from->sb_sectlog;
    to->sb_inodelog = from->sb_inodelog;
    to->sb_inopblog = from->sb_inopblog;
    to->sb_agblklog = from->sb_agblklog;
    to->sb_rextslog = from->sb_rextslog;
    to->sb_inprogress = from->sb_inprogress;
    to->sb_imax_pct = from->sb_imax_pct;
    to->sb_icount = be64_to_cpu(from->sb_icount);
    to->sb_ifree = be64_to_cpu(from->sb_ifree);
    to->sb_fdblocks = be64_to_cpu(from->sb_fdblocks);
    to->sb_frextents = be64_to_cpu(from->sb_frextents);
    to->sb_uquotino = be64_to_cpu(from->sb_uquotino);
    to->sb_gquotino = be64_to_cpu(from->sb_gquotino);
    to->sb_qflags = be16_to_cpu(from->sb_qflags);
    to->sb_flags = from->sb_flags;
    to->sb_shared_vn = from->sb_shared_vn;
    to->sb_inoalignmt = be32_to_cpu(from->sb_inoalignmt);
    to->sb_unit = be32_to_cpu(from->sb_unit);
    to->sb_width = be32_to_cpu(from->sb_width);
    to->sb_dirblklog = from->sb_dirblklog;
    to->sb_logsectlog = from->sb_logsectlog;
    to->sb_logsectsize = be16_to_cpu(from->sb_logsectsize);
    to->sb_logsunit = be32_to_cpu(from->sb_logsunit);
    to->sb_features2 = be32_to_cpu(from->sb_features2);
    to->sb_bad_features2 = be32_to_cpu(from->sb_bad_features2);
}

/*
 * Copy in core superblock to ondisk one.
 *
 * The fields argument is mask of superblock fields to copy.
 */
void
xfs_sb_to_disk(
    xfs_dsb_t   *to,
    xfs_sb_t    *from,
    __int64_t   fields)
{
    xfs_caddr_t to_ptr = (xfs_caddr_t)to;
    xfs_caddr_t from_ptr = (xfs_caddr_t)from;
    xfs_sb_field_t  f;
    int     first;
    int     size;

    ASSERT(fields);
    if (!fields)
        return;

    while (fields) {
        f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
        first = xfs_sb_info[f].offset;
        size = xfs_sb_info[f + 1].offset - first;

        ASSERT(xfs_sb_info[f].type == 0 || xfs_sb_info[f].type == 1);

        if (size == 1 || xfs_sb_info[f].type == 1) {
            memcpy(to_ptr + first, from_ptr + first, size);
        } else {
            switch (size) {
            case 2:
                *(__be16 *)(to_ptr + first) =
                    cpu_to_be16(*(__u16 *)(from_ptr + first));
                break;
            case 4:
                *(__be32 *)(to_ptr + first) =
                    cpu_to_be32(*(__u32 *)(from_ptr + first));
                break;
            case 8:
                *(__be64 *)(to_ptr + first) =
                    cpu_to_be64(*(__u64 *)(from_ptr + first));
                break;
            default:
                ASSERT(0);
            }
        }

        fields &= ~(1LL << f);
    }
}

/*
 * xfs_readsb
 *
 * Does the initial read of the superblock.
 */
int
xfs_readsb(xfs_mount_t *mp, int flags)
{
    unsigned int    sector_size;
    xfs_buf_t   *bp;
    int     error;
    int     loud = !(flags & XFS_MFSI_QUIET);

    ASSERT(mp->m_sb_bp == NULL);
    ASSERT(mp->m_ddev_targp != NULL);

    /*
     * Allocate a (locked) buffer to hold the superblock.
     * This will be kept around at all times to optimize
     * access to the superblock.
     */
    sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);

reread:
    bp = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
                    BTOBB(sector_size), 0);
    if (!bp) {
        if (loud)
            xfs_warn(mp, "SB buffer read failed");
        return EIO;
    }

    /*
     * Initialize the mount structure from the superblock.
     * But first do some basic consistency checking.
     */
    xfs_sb_from_disk(mp, XFS_BUF_TO_SBP(bp));
    error = xfs_mount_validate_sb(mp, &(mp->m_sb), flags);
    if (error) {
        if (loud)
            xfs_warn(mp, "SB validate failed");
        goto release_buf;
    }

    /*
     * We must be able to do sector-sized and sector-aligned IO.
     */
    if (sector_size > mp->m_sb.sb_sectsize) {
        if (loud)
            xfs_warn(mp, "device supports %u byte sectors (not %u)",
                sector_size, mp->m_sb.sb_sectsize);
        error = ENOSYS;
        goto release_buf;
    }

    /*
     * If device sector size is smaller than the superblock size,
     * re-read the superblock so the buffer is correctly sized.
     */
    if (sector_size < mp->m_sb.sb_sectsize) {
        xfs_buf_relse(bp);
        sector_size = mp->m_sb.sb_sectsize;
        goto reread;
    }

    /* Initialize per-cpu counters */
    xfs_icsb_reinit_counters(mp);

    mp->m_sb_bp = bp;
    xfs_buf_unlock(bp);
    return 0;

release_buf:
    xfs_buf_relse(bp);
    return error;
}


/*
 * xfs_mount_common
 *
 * Mount initialization code establishing various mount
 * fields from the superblock associated with the given
 * mount structure
 */
STATIC void
xfs_mount_common(xfs_mount_t *mp, xfs_sb_t *sbp)
{
    mp->m_agfrotor = mp->m_agirotor = 0;
    spin_lock_init(&mp->m_agirotor_lock);
    mp->m_maxagi = mp->m_sb.sb_agcount;
    mp->m_blkbit_log = sbp->sb_blocklog + XFS_NBBYLOG;
    mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
    mp->m_sectbb_log = sbp->sb_sectlog - BBSHIFT;
    mp->m_agno_log = xfs_highbit32(sbp->sb_agcount - 1) + 1;
    mp->m_agino_log = sbp->sb_inopblog + sbp->sb_agblklog;
    mp->m_blockmask = sbp->sb_blocksize - 1;
    mp->m_blockwsize = sbp->sb_blocksize >> XFS_WORDLOG;
    mp->m_blockwmask = mp->m_blockwsize - 1;

    mp->m_alloc_mxr[0] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 1);
    mp->m_alloc_mxr[1] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 0);
    mp->m_alloc_mnr[0] = mp->m_alloc_mxr[0] / 2;
    mp->m_alloc_mnr[1] = mp->m_alloc_mxr[1] / 2;

    mp->m_inobt_mxr[0] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 1);
    mp->m_inobt_mxr[1] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 0);
    mp->m_inobt_mnr[0] = mp->m_inobt_mxr[0] / 2;
    mp->m_inobt_mnr[1] = mp->m_inobt_mxr[1] / 2;

    mp->m_bmap_dmxr[0] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 1);
    mp->m_bmap_dmxr[1] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 0);
    mp->m_bmap_dmnr[0] = mp->m_bmap_dmxr[0] / 2;
    mp->m_bmap_dmnr[1] = mp->m_bmap_dmxr[1] / 2;

    mp->m_bsize = XFS_FSB_TO_BB(mp, 1);
    mp->m_ialloc_inos = (int)MAX((__uint16_t)XFS_INODES_PER_CHUNK,
                    sbp->sb_inopblock);
    mp->m_ialloc_blks = mp->m_ialloc_inos >> sbp->sb_inopblog;
}

/*
 * xfs_initialize_perag_data
 *
 * Read in each per-ag structure so we can count up the number of
 * allocated inodes, free inodes and used filesystem blocks as this
 * information is no longer persistent in the superblock. Once we have
 * this information, write it into the in-core superblock structure.
 */
STATIC int
xfs_initialize_perag_data(xfs_mount_t *mp, xfs_agnumber_t agcount)
{
    xfs_agnumber_t  index;
    xfs_perag_t *pag;
    xfs_sb_t    *sbp = &mp->m_sb;
    uint64_t    ifree = 0;
    uint64_t    ialloc = 0;
    uint64_t    bfree = 0;
    uint64_t    bfreelst = 0;
    uint64_t    btree = 0;
    int     error;

    for (index = 0; index < agcount; index++) {
        /*
         * read the agf, then the agi. This gets us
         * all the information we need and populates the
         * per-ag structures for us.
         */
        error = xfs_alloc_pagf_init(mp, NULL, index, 0);
        if (error)
            return error;

        error = xfs_ialloc_pagi_init(mp, NULL, index);
        if (error)
            return error;
        pag = xfs_perag_get(mp, index);
        ifree += pag->pagi_freecount;
        ialloc += pag->pagi_count;
        bfree += pag->pagf_freeblks;
        bfreelst += pag->pagf_flcount;
        btree += pag->pagf_btreeblks;
        xfs_perag_put(pag);
    }
    /*
     * Overwrite incore superblock counters with just-read data
     */
    spin_lock(&mp->m_sb_lock);
    sbp->sb_ifree = ifree;
    sbp->sb_icount = ialloc;
    sbp->sb_fdblocks = bfree + bfreelst + btree;
    spin_unlock(&mp->m_sb_lock);

    /* Fixup the per-cpu counters as well. */
    xfs_icsb_reinit_counters(mp);

    return 0;
}

/*
 * Update alignment values based on mount options and sb values
 */
STATIC int
xfs_update_alignment(xfs_mount_t *mp)
{
    xfs_sb_t    *sbp = &(mp->m_sb);

    if (mp->m_dalign) {
        /*
         * If stripe unit and stripe width are not multiples
         * of the fs blocksize turn off alignment.
         */
        if ((BBTOB(mp->m_dalign) & mp->m_blockmask) ||
            (BBTOB(mp->m_swidth) & mp->m_blockmask)) {
            if (mp->m_flags & XFS_MOUNT_RETERR) {
                xfs_warn(mp, "alignment check failed: "
                     "(sunit/swidth vs. blocksize)");
                return XFS_ERROR(EINVAL);
            }
            mp->m_dalign = mp->m_swidth = 0;
        } else {
            /*
             * Convert the stripe unit and width to FSBs.
             */
            mp->m_dalign = XFS_BB_TO_FSBT(mp, mp->m_dalign);
            if (mp->m_dalign && (sbp->sb_agblocks % mp->m_dalign)) {
                if (mp->m_flags & XFS_MOUNT_RETERR) {
                    xfs_warn(mp, "alignment check failed: "
                         "(sunit/swidth vs. ag size)");
                    return XFS_ERROR(EINVAL);
                }
                xfs_warn(mp,
        "stripe alignment turned off: sunit(%d)/swidth(%d) "
        "incompatible with agsize(%d)",
                    mp->m_dalign, mp->m_swidth,
                    sbp->sb_agblocks);

                mp->m_dalign = 0;
                mp->m_swidth = 0;
            } else if (mp->m_dalign) {
                mp->m_swidth = XFS_BB_TO_FSBT(mp, mp->m_swidth);
            } else {
                if (mp->m_flags & XFS_MOUNT_RETERR) {
                    xfs_warn(mp, "alignment check failed: "
                        "sunit(%d) less than bsize(%d)",
                        mp->m_dalign,
                        mp->m_blockmask +1);
                    return XFS_ERROR(EINVAL);
                }
                mp->m_swidth = 0;
            }
        }

        /*
         * Update superblock with new values
         * and log changes
         */
        if (xfs_sb_version_hasdalign(sbp)) {
            if (sbp->sb_unit != mp->m_dalign) {
                sbp->sb_unit = mp->m_dalign;
                mp->m_update_flags |= XFS_SB_UNIT;
            }
            if (sbp->sb_width != mp->m_swidth) {
                sbp->sb_width = mp->m_swidth;
                mp->m_update_flags |= XFS_SB_WIDTH;
            }
        }
    } else if ((mp->m_flags & XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN &&
            xfs_sb_version_hasdalign(&mp->m_sb)) {
            mp->m_dalign = sbp->sb_unit;
            mp->m_swidth = sbp->sb_width;
    }

    return 0;
}

/*
 * Set the maximum inode count for this filesystem
 */
STATIC void
xfs_set_maxicount(xfs_mount_t *mp)
{
    xfs_sb_t    *sbp = &(mp->m_sb);
    __uint64_t  icount;

    if (sbp->sb_imax_pct) {
        /*
         * Make sure the maximum inode count is a multiple
         * of the units we allocate inodes in.
         */
        icount = sbp->sb_dblocks * sbp->sb_imax_pct;
        do_div(icount, 100);
        do_div(icount, mp->m_ialloc_blks);
        mp->m_maxicount = (icount * mp->m_ialloc_blks)  <<
                   sbp->sb_inopblog;
    } else {
        mp->m_maxicount = 0;
    }
}

/*
 * Set the default minimum read and write sizes unless
 * already specified in a mount option.
 * We use smaller I/O sizes when the file system
 * is being used for NFS service (wsync mount option).
 */
STATIC void
xfs_set_rw_sizes(xfs_mount_t *mp)
{
    xfs_sb_t    *sbp = &(mp->m_sb);
    int     readio_log, writeio_log;

    if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
        if (mp->m_flags & XFS_MOUNT_WSYNC) {
            readio_log = XFS_WSYNC_READIO_LOG;
            writeio_log = XFS_WSYNC_WRITEIO_LOG;
        } else {
            readio_log = XFS_READIO_LOG_LARGE;
            writeio_log = XFS_WRITEIO_LOG_LARGE;
        }
    } else {
        readio_log = mp->m_readio_log;
        writeio_log = mp->m_writeio_log;
    }

    if (sbp->sb_blocklog > readio_log) {
        mp->m_readio_log = sbp->sb_blocklog;
    } else {
        mp->m_readio_log = readio_log;
    }
    mp->m_readio_blocks = 1 << (mp->m_readio_log - sbp->sb_blocklog);
    if (sbp->sb_blocklog > writeio_log) {
        mp->m_writeio_log = sbp->sb_blocklog;
    } else {
        mp->m_writeio_log = writeio_log;
    }
    mp->m_writeio_blocks = 1 << (mp->m_writeio_log - sbp->sb_blocklog);
}

/*
 * precalculate the low space thresholds for dynamic speculative preallocation.
 */
void
xfs_set_low_space_thresholds(
    struct xfs_mount    *mp)
{
    int i;

    for (i = 0; i < XFS_LOWSP_MAX; i++) {
        __uint64_t space = mp->m_sb.sb_dblocks;

        do_div(space, 100);
        mp->m_low_space[i] = space * (i + 1);
    }
}


/*
 * Set whether we're using inode alignment.
 */
STATIC void
xfs_set_inoalignment(xfs_mount_t *mp)
{
    if (xfs_sb_version_hasalign(&mp->m_sb) &&
        mp->m_sb.sb_inoalignmt >=
        XFS_B_TO_FSBT(mp, mp->m_inode_cluster_size))
        mp->m_inoalign_mask = mp->m_sb.sb_inoalignmt - 1;
    else
        mp->m_inoalign_mask = 0;
    /*
     * If we are using stripe alignment, check whether
     * the stripe unit is a multiple of the inode alignment
     */
    if (mp->m_dalign && mp->m_inoalign_mask &&
        !(mp->m_dalign & mp->m_inoalign_mask))
        mp->m_sinoalign = mp->m_dalign;
    else
        mp->m_sinoalign = 0;
}

/*
 * Check that the data (and log if separate) are an ok size.
 */
STATIC int
xfs_check_sizes(xfs_mount_t *mp)
{
    xfs_buf_t   *bp;
    xfs_daddr_t d;

    d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
    if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_dblocks) {
        xfs_warn(mp, "filesystem size mismatch detected");
        return XFS_ERROR(EFBIG);
    }
    bp = xfs_buf_read_uncached(mp->m_ddev_targp,
                    d - XFS_FSS_TO_BB(mp, 1),
                    XFS_FSS_TO_BB(mp, 1), 0);
    if (!bp) {
        xfs_warn(mp, "last sector read failed");
        return EIO;
    }
    xfs_buf_relse(bp);

    if (mp->m_logdev_targp != mp->m_ddev_targp) {
        d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks);
        if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_logblocks) {
            xfs_warn(mp, "log size mismatch detected");
            return XFS_ERROR(EFBIG);
        }
        bp = xfs_buf_read_uncached(mp->m_logdev_targp,
                    d - XFS_FSB_TO_BB(mp, 1),
                    XFS_FSB_TO_BB(mp, 1), 0);
        if (!bp) {
            xfs_warn(mp, "log device read failed");
            return EIO;
        }
        xfs_buf_relse(bp);
    }
    return 0;
}

/*
 * Clear the quotaflags in memory and in the superblock.
 */
int
xfs_mount_reset_sbqflags(
    struct xfs_mount    *mp)
{
    int         error;
    struct xfs_trans    *tp;

    mp->m_qflags = 0;

    /*
     * It is OK to look at sb_qflags here in mount path,
     * without m_sb_lock.
     */
    if (mp->m_sb.sb_qflags == 0)
        return 0;
    spin_lock(&mp->m_sb_lock);
    mp->m_sb.sb_qflags = 0;
    spin_unlock(&mp->m_sb_lock);

    /*
     * If the fs is readonly, let the incore superblock run
     * with quotas off but don't flush the update out to disk
     */
    if (mp->m_flags & XFS_MOUNT_RDONLY)
        return 0;

    tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SBCHANGE);
    error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
                      XFS_DEFAULT_LOG_COUNT);
    if (error) {
        xfs_trans_cancel(tp, 0);
        xfs_alert(mp, "%s: Superblock update failed!", __func__);
        return error;
    }

    xfs_mod_sb(tp, XFS_SB_QFLAGS);
    return xfs_trans_commit(tp, 0);
}

__uint64_t
xfs_default_resblks(xfs_mount_t *mp)
{
    __uint64_t resblks;

    /*
     * We default to 5% or 8192 fsbs of space reserved, whichever is
     * smaller.  This is intended to cover concurrent allocation
     * transactions when we initially hit enospc. These each require a 4
     * block reservation. Hence by default we cover roughly 2000 concurrent
     * allocation reservations.
     */
    resblks = mp->m_sb.sb_dblocks;
    do_div(resblks, 20);
    resblks = min_t(__uint64_t, resblks, 8192);
    return resblks;
}

/*
 * This function does the following on an initial mount of a file system:
 *  - reads the superblock from disk and init the mount struct
 *  - if we're a 32-bit kernel, do a size check on the superblock
 *      so we don't mount terabyte filesystems
 *  - init mount struct realtime fields
 *  - allocate inode hash table for fs
 *  - init directory manager
 *  - perform recovery and init the log manager
 */
int
xfs_mountfs(
    xfs_mount_t *mp)
{
    xfs_sb_t    *sbp = &(mp->m_sb);
    xfs_inode_t *rip;
    __uint64_t  resblks;
    uint        quotamount = 0;
    uint        quotaflags = 0;
    int     error = 0;

    xfs_mount_common(mp, sbp);

    /*
     * Check for a mismatched features2 values.  Older kernels
     * read & wrote into the wrong sb offset for sb_features2
     * on some platforms due to xfs_sb_t not being 64bit size aligned
     * when sb_features2 was added, which made older superblock
     * reading/writing routines swap it as a 64-bit value.
     *
     * For backwards compatibility, we make both slots equal.
     *
     * If we detect a mismatched field, we OR the set bits into the
     * existing features2 field in case it has already been modified; we
     * don't want to lose any features.  We then update the bad location
     * with the ORed value so that older kernels will see any features2
     * flags, and mark the two fields as needing updates once the
     * transaction subsystem is online.
     */
    if (xfs_sb_has_mismatched_features2(sbp)) {
        xfs_warn(mp, "correcting sb_features alignment problem");
        sbp->sb_features2 |= sbp->sb_bad_features2;
        sbp->sb_bad_features2 = sbp->sb_features2;
        mp->m_update_flags |= XFS_SB_FEATURES2 | XFS_SB_BAD_FEATURES2;

        /*
         * Re-check for ATTR2 in case it was found in bad_features2
         * slot.
         */
        if (xfs_sb_version_hasattr2(&mp->m_sb) &&
           !(mp->m_flags & XFS_MOUNT_NOATTR2))
            mp->m_flags |= XFS_MOUNT_ATTR2;
    }

    if (xfs_sb_version_hasattr2(&mp->m_sb) &&
       (mp->m_flags & XFS_MOUNT_NOATTR2)) {
        xfs_sb_version_removeattr2(&mp->m_sb);
        mp->m_update_flags |= XFS_SB_FEATURES2;

        /* update sb_versionnum for the clearing of the morebits */
        if (!sbp->sb_features2)
            mp->m_update_flags |= XFS_SB_VERSIONNUM;
    }

    /*
     * Check if sb_agblocks is aligned at stripe boundary
     * If sb_agblocks is NOT aligned turn off m_dalign since
     * allocator alignment is within an ag, therefore ag has
     * to be aligned at stripe boundary.
     */
    error = xfs_update_alignment(mp);
    if (error)
        goto out;

    xfs_alloc_compute_maxlevels(mp);
    xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK);
    xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK);
    xfs_ialloc_compute_maxlevels(mp);

    xfs_set_maxicount(mp);

    error = xfs_uuid_mount(mp);
    if (error)
        goto out;

    /*
     * Set the minimum read and write sizes
     */
    xfs_set_rw_sizes(mp);

    /* set the low space thresholds for dynamic preallocation */
    xfs_set_low_space_thresholds(mp);

    /*
     * Set the inode cluster size.
     * This may still be overridden by the file system
     * block size if it is larger than the chosen cluster size.
     */
    mp->m_inode_cluster_size = XFS_INODE_BIG_CLUSTER_SIZE;

    /*
     * Set inode alignment fields
     */
    xfs_set_inoalignment(mp);

    /*
     * Check that the data (and log if separate) are an ok size.
     */
    error = xfs_check_sizes(mp);
    if (error)
        goto out_remove_uuid;

    /*
     * Initialize realtime fields in the mount structure
     */
    error = xfs_rtmount_init(mp);
    if (error) {
        xfs_warn(mp, "RT mount failed");
        goto out_remove_uuid;
    }

    /*
     *  Copies the low order bits of the timestamp and the randomly
     *  set "sequence" number out of a UUID.
     */
    uuid_getnodeuniq(&sbp->sb_uuid, mp->m_fixedfsid);

    mp->m_dmevmask = 0; /* not persistent; set after each mount */

    xfs_dir_mount(mp);

    /*
     * Initialize the attribute manager's entries.
     */
    mp->m_attr_magicpct = (mp->m_sb.sb_blocksize * 37) / 100;

    /*
     * Initialize the precomputed transaction reservations values.
     */
    xfs_trans_init(mp);

    /*
     * Allocate and initialize the per-ag data.
     */
    spin_lock_init(&mp->m_perag_lock);
    INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
    error = xfs_initialize_perag(mp, sbp->sb_agcount, &mp->m_maxagi);
    if (error) {
        xfs_warn(mp, "Failed per-ag init: %d", error);
        goto out_remove_uuid;
    }

    if (!sbp->sb_logblocks) {
        xfs_warn(mp, "no log defined");
        XFS_ERROR_REPORT("xfs_mountfs", XFS_ERRLEVEL_LOW, mp);
        error = XFS_ERROR(EFSCORRUPTED);
        goto out_free_perag;
    }

    /*
     * log's mount-time initialization. Perform 1st part recovery if needed
     */
    error = xfs_log_mount(mp, mp->m_logdev_targp,
                  XFS_FSB_TO_DADDR(mp, sbp->sb_logstart),
                  XFS_FSB_TO_BB(mp, sbp->sb_logblocks));
    if (error) {
        xfs_warn(mp, "log mount failed");
        goto out_fail_wait;
    }

    /*
     * Now the log is mounted, we know if it was an unclean shutdown or
     * not. If it was, with the first phase of recovery has completed, we
     * have consistent AG blocks on disk. We have not recovered EFIs yet,
     * but they are recovered transactionally in the second recovery phase
     * later.
     *
     * Hence we can safely re-initialise incore superblock counters from
     * the per-ag data. These may not be correct if the filesystem was not
     * cleanly unmounted, so we need to wait for recovery to finish before
     * doing this.
     *
     * If the filesystem was cleanly unmounted, then we can trust the
     * values in the superblock to be correct and we don't need to do
     * anything here.
     *
     * If we are currently making the filesystem, the initialisation will
     * fail as the perag data is in an undefined state.
     */
    if (xfs_sb_version_haslazysbcount(&mp->m_sb) &&
        !XFS_LAST_UNMOUNT_WAS_CLEAN(mp) &&
         !mp->m_sb.sb_inprogress) {
        error = xfs_initialize_perag_data(mp, sbp->sb_agcount);
        if (error)
            goto out_fail_wait;
    }

    /*
     * Get and sanity-check the root inode.
     * Save the pointer to it in the mount structure.
     */
    error = xfs_iget(mp, NULL, sbp->sb_rootino, 0, XFS_ILOCK_EXCL, &rip);
    if (error) {
        xfs_warn(mp, "failed to read root inode");
        goto out_log_dealloc;
    }

    ASSERT(rip != NULL);

    if (unlikely(!S_ISDIR(rip->i_d.di_mode))) {
        xfs_warn(mp, "corrupted root inode %llu: not a directory",
            (unsigned long long)rip->i_ino);
        xfs_iunlock(rip, XFS_ILOCK_EXCL);
        XFS_ERROR_REPORT("xfs_mountfs_int(2)", XFS_ERRLEVEL_LOW,
                 mp);
        error = XFS_ERROR(EFSCORRUPTED);
        goto out_rele_rip;
    }
    mp->m_rootip = rip; /* save it */

    xfs_iunlock(rip, XFS_ILOCK_EXCL);

    /*
     * Initialize realtime inode pointers in the mount structure
     */
    error = xfs_rtmount_inodes(mp);
    if (error) {
        /*
         * Free up the root inode.
         */
        xfs_warn(mp, "failed to read RT inodes");
        goto out_rele_rip;
    }

    /*
     * If this is a read-only mount defer the superblock updates until
     * the next remount into writeable mode.  Otherwise we would never
     * perform the update e.g. for the root filesystem.
     */
    if (mp->m_update_flags && !(mp->m_flags & XFS_MOUNT_RDONLY)) {
        error = xfs_mount_log_sb(mp, mp->m_update_flags);
        if (error) {
            xfs_warn(mp, "failed to write sb changes");
            goto out_rtunmount;
        }
    }

    /*
     * Initialise the XFS quota management subsystem for this mount
     */
    if (XFS_IS_QUOTA_RUNNING(mp)) {
        error = xfs_qm_newmount(mp, &quotamount, &quotaflags);
        if (error)
            goto out_rtunmount;
    } else {
        ASSERT(!XFS_IS_QUOTA_ON(mp));

        /*
         * If a file system had quotas running earlier, but decided to
         * mount without -o uquota/pquota/gquota options, revoke the
         * quotachecked license.
         */
        if (mp->m_sb.sb_qflags & XFS_ALL_QUOTA_ACCT) {
            xfs_notice(mp, "resetting quota flags");
            error = xfs_mount_reset_sbqflags(mp);
            if (error)
                return error;
        }
    }

    /*
     * Finish recovering the file system.  This part needed to be
     * delayed until after the root and real-time bitmap inodes
     * were consistently read in.
     */
    error = xfs_log_mount_finish(mp);
    if (error) {
        xfs_warn(mp, "log mount finish failed");
        goto out_rtunmount;
    }

    /*
     * Complete the quota initialisation, post-log-replay component.
     */
    if (quotamount) {
        ASSERT(mp->m_qflags == 0);
        mp->m_qflags = quotaflags;

        xfs_qm_mount_quotas(mp);
    }

    /*
     * Now we are mounted, reserve a small amount of unused space for
     * privileged transactions. This is needed so that transaction
     * space required for critical operations can dip into this pool
     * when at ENOSPC. This is needed for operations like create with
     * attr, unwritten extent conversion at ENOSPC, etc. Data allocations
     * are not allowed to use this reserved space.
     *
     * This may drive us straight to ENOSPC on mount, but that implies
     * we were already there on the last unmount. Warn if this occurs.
     */
    if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
        resblks = xfs_default_resblks(mp);
        error = xfs_reserve_blocks(mp, &resblks, NULL);
        if (error)
            xfs_warn(mp,
    "Unable to allocate reserve blocks. Continuing without reserve pool.");
    }

    return 0;

 out_rtunmount:
    xfs_rtunmount_inodes(mp);
 out_rele_rip:
    IRELE(rip);
 out_log_dealloc:
    xfs_log_unmount(mp);
 out_fail_wait:
    if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
        xfs_wait_buftarg(mp->m_logdev_targp);
    xfs_wait_buftarg(mp->m_ddev_targp);
 out_free_perag:
    xfs_free_perag(mp);
 out_remove_uuid:
    xfs_uuid_unmount(mp);
 out:
    return error;
}

/*
 * This flushes out the inodes,dquots and the superblock, unmounts the
 * log and makes sure that incore structures are freed.
 */
void
xfs_unmountfs(
    struct xfs_mount    *mp)
{
    __uint64_t      resblks;
    int         error;

    xfs_qm_unmount_quotas(mp);
    xfs_rtunmount_inodes(mp);
    IRELE(mp->m_rootip);

    /*
     * We can potentially deadlock here if we have an inode cluster
     * that has been freed has its buffer still pinned in memory because
     * the transaction is still sitting in a iclog. The stale inodes
     * on that buffer will have their flush locks held until the
     * transaction hits the disk and the callbacks run. the inode
     * flush takes the flush lock unconditionally and with nothing to
     * push out the iclog we will never get that unlocked. hence we
     * need to force the log first.
     */
    xfs_log_force(mp, XFS_LOG_SYNC);

    /*
     * Flush all pending changes from the AIL.
     */
    xfs_ail_push_all_sync(mp->m_ail);

    /*
     * And reclaim all inodes.  At this point there should be no dirty
     * inode, and none should be pinned or locked, but use synchronous
     * reclaim just to be sure.
     */
    xfs_reclaim_inodes(mp, SYNC_WAIT);

    xfs_qm_unmount(mp);

    /*
     * Flush out the log synchronously so that we know for sure
     * that nothing is pinned.  This is important because bflush()
     * will skip pinned buffers.
     */
    xfs_log_force(mp, XFS_LOG_SYNC);

    /*
     * Unreserve any blocks we have so that when we unmount we don't account
     * the reserved free space as used. This is really only necessary for
     * lazy superblock counting because it trusts the incore superblock
     * counters to be absolutely correct on clean unmount.
     *
     * We don't bother correcting this elsewhere for lazy superblock
     * counting because on mount of an unclean filesystem we reconstruct the
     * correct counter value and this is irrelevant.
     *
     * For non-lazy counter filesystems, this doesn't matter at all because
     * we only every apply deltas to the superblock and hence the incore
     * value does not matter....
     */
    resblks = 0;
    error = xfs_reserve_blocks(mp, &resblks, NULL);
    if (error)
        xfs_warn(mp, "Unable to free reserved block pool. "
                "Freespace may not be correct on next mount.");

    error = xfs_log_sbcount(mp);
    if (error)
        xfs_warn(mp, "Unable to update superblock counters. "
                "Freespace may not be correct on next mount.");

    /*
     * At this point we might have modified the superblock again and thus
     * added an item to the AIL, thus flush it again.
     */
    xfs_ail_push_all_sync(mp->m_ail);
    xfs_wait_buftarg(mp->m_ddev_targp);

    /*
     * The superblock buffer is uncached and xfsaild_push() will lock and
     * set the XBF_ASYNC flag on the buffer. We cannot do xfs_buf_iowait()
     * here but a lock on the superblock buffer will block until iodone()
     * has completed.
     */
    xfs_buf_lock(mp->m_sb_bp);
    xfs_buf_unlock(mp->m_sb_bp);

    xfs_log_unmount_write(mp);
    xfs_log_unmount(mp);
    xfs_uuid_unmount(mp);

#if defined(DEBUG)
    xfs_errortag_clearall(mp, 0);
#endif
    xfs_free_perag(mp);
}

int
xfs_fs_writable(xfs_mount_t *mp)
{
    return !(mp->m_super->s_writers.frozen || XFS_FORCED_SHUTDOWN(mp) ||
        (mp->m_flags & XFS_MOUNT_RDONLY));
}

/*
 * xfs_log_sbcount
 *
 * Sync the superblock counters to disk.
 *
 * Note this code can be called during the process of freezing, so
 * we may need to use the transaction allocator which does not
 * block when the transaction subsystem is in its frozen state.
 */
int
xfs_log_sbcount(xfs_mount_t *mp)
{
    xfs_trans_t *tp;
    int     error;

    if (!xfs_fs_writable(mp))
        return 0;

    xfs_icsb_sync_counters(mp, 0);

    /*
     * we don't need to do this if we are updating the superblock
     * counters on every modification.
     */
    if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
        return 0;

    tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP);
    error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
                    XFS_DEFAULT_LOG_COUNT);
    if (error) {
        xfs_trans_cancel(tp, 0);
        return error;
    }

    xfs_mod_sb(tp, XFS_SB_IFREE | XFS_SB_ICOUNT | XFS_SB_FDBLOCKS);
    xfs_trans_set_sync(tp);
    error = xfs_trans_commit(tp, 0);
    return error;
}

/*
 * xfs_mod_sb() can be used to copy arbitrary changes to the
 * in-core superblock into the superblock buffer to be logged.
 * It does not provide the higher level of locking that is
 * needed to protect the in-core superblock from concurrent
 * access.
 */
void
xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
{
    xfs_buf_t   *bp;
    int     first;
    int     last;
    xfs_mount_t *mp;
    xfs_sb_field_t  f;

    ASSERT(fields);
    if (!fields)
        return;
    mp = tp->t_mountp;
    bp = xfs_trans_getsb(tp, mp, 0);
    first = sizeof(xfs_sb_t);
    last = 0;

    /* translate/copy */

    xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, fields);

    /* find modified range */
    f = (xfs_sb_field_t)xfs_highbit64((__uint64_t)fields);
    ASSERT((1LL << f) & XFS_SB_MOD_BITS);
    last = xfs_sb_info[f + 1].offset - 1;

    f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
    ASSERT((1LL << f) & XFS_SB_MOD_BITS);
    first = xfs_sb_info[f].offset;

    xfs_trans_log_buf(tp, bp, first, last);
}


/*
 * xfs_mod_incore_sb_unlocked() is a utility routine common used to apply
 * a delta to a specified field in the in-core superblock.  Simply
 * switch on the field indicated and apply the delta to that field.
 * Fields are not allowed to dip below zero, so if the delta would
 * do this do not apply it and return EINVAL.
 *
 * The m_sb_lock must be held when this routine is called.
 */
STATIC int
xfs_mod_incore_sb_unlocked(
    xfs_mount_t *mp,
    xfs_sb_field_t  field,
    int64_t     delta,
    int     rsvd)
{
    int     scounter;   /* short counter for 32 bit fields */
    long long   lcounter;   /* long counter for 64 bit fields */
    long long   res_used, rem;

    /*
     * With the in-core superblock spin lock held, switch
     * on the indicated field.  Apply the delta to the
     * proper field.  If the fields value would dip below
     * 0, then do not apply the delta and return EINVAL.
     */
    switch (field) {
    case XFS_SBS_ICOUNT:
        lcounter = (long long)mp->m_sb.sb_icount;
        lcounter += delta;
        if (lcounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_icount = lcounter;
        return 0;
    case XFS_SBS_IFREE:
        lcounter = (long long)mp->m_sb.sb_ifree;
        lcounter += delta;
        if (lcounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_ifree = lcounter;
        return 0;
    case XFS_SBS_FDBLOCKS:
        lcounter = (long long)
            mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
        res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);

        if (delta > 0) {        /* Putting blocks back */
            if (res_used > delta) {
                mp->m_resblks_avail += delta;
            } else {
                rem = delta - res_used;
                mp->m_resblks_avail = mp->m_resblks;
                lcounter += rem;
            }
        } else {                /* Taking blocks away */
            lcounter += delta;
            if (lcounter >= 0) {
                mp->m_sb.sb_fdblocks = lcounter +
                            XFS_ALLOC_SET_ASIDE(mp);
                return 0;
            }

            /*
             * We are out of blocks, use any available reserved
             * blocks if were allowed to.
             */
            if (!rsvd)
                return XFS_ERROR(ENOSPC);

            lcounter = (long long)mp->m_resblks_avail + delta;
            if (lcounter >= 0) {
                mp->m_resblks_avail = lcounter;
                return 0;
            }
            printk_once(KERN_WARNING
                "Filesystem \"%s\": reserve blocks depleted! "
                "Consider increasing reserve pool size.",
                mp->m_fsname);
            return XFS_ERROR(ENOSPC);
        }

        mp->m_sb.sb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
        return 0;
    case XFS_SBS_FREXTENTS:
        lcounter = (long long)mp->m_sb.sb_frextents;
        lcounter += delta;
        if (lcounter < 0) {
            return XFS_ERROR(ENOSPC);
        }
        mp->m_sb.sb_frextents = lcounter;
        return 0;
    case XFS_SBS_DBLOCKS:
        lcounter = (long long)mp->m_sb.sb_dblocks;
        lcounter += delta;
        if (lcounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_dblocks = lcounter;
        return 0;
    case XFS_SBS_AGCOUNT:
        scounter = mp->m_sb.sb_agcount;
        scounter += delta;
        if (scounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_agcount = scounter;
        return 0;
    case XFS_SBS_IMAX_PCT:
        scounter = mp->m_sb.sb_imax_pct;
        scounter += delta;
        if (scounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_imax_pct = scounter;
        return 0;
    case XFS_SBS_REXTSIZE:
        scounter = mp->m_sb.sb_rextsize;
        scounter += delta;
        if (scounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_rextsize = scounter;
        return 0;
    case XFS_SBS_RBMBLOCKS:
        scounter = mp->m_sb.sb_rbmblocks;
        scounter += delta;
        if (scounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_rbmblocks = scounter;
        return 0;
    case XFS_SBS_RBLOCKS:
        lcounter = (long long)mp->m_sb.sb_rblocks;
        lcounter += delta;
        if (lcounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_rblocks = lcounter;
        return 0;
    case XFS_SBS_REXTENTS:
        lcounter = (long long)mp->m_sb.sb_rextents;
        lcounter += delta;
        if (lcounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_rextents = lcounter;
        return 0;
    case XFS_SBS_REXTSLOG:
        scounter = mp->m_sb.sb_rextslog;
        scounter += delta;
        if (scounter < 0) {
            ASSERT(0);
            return XFS_ERROR(EINVAL);
        }
        mp->m_sb.sb_rextslog = scounter;
        return 0;
    default:
        ASSERT(0);
        return XFS_ERROR(EINVAL);
    }
}

/*
 * xfs_mod_incore_sb() is used to change a field in the in-core
 * superblock structure by the specified delta.  This modification
 * is protected by the m_sb_lock.  Just use the xfs_mod_incore_sb_unlocked()
 * routine to do the work.
 */
int
xfs_mod_incore_sb(
    struct xfs_mount    *mp,
    xfs_sb_field_t      field,
    int64_t         delta,
    int         rsvd)
{
    int         status;

#ifdef HAVE_PERCPU_SB
    ASSERT(field < XFS_SBS_ICOUNT || field > XFS_SBS_FDBLOCKS);
#endif
    spin_lock(&mp->m_sb_lock);
    status = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd);
    spin_unlock(&mp->m_sb_lock);

    return status;
}

/*
 * Change more than one field in the in-core superblock structure at a time.
 *
 * The fields and changes to those fields are specified in the array of
 * xfs_mod_sb structures passed in.  Either all of the specified deltas
 * will be applied or none of them will.  If any modified field dips below 0,
 * then all modifications will be backed out and EINVAL will be returned.
 *
 * Note that this function may not be used for the superblock values that
 * are tracked with the in-memory per-cpu counters - a direct call to
 * xfs_icsb_modify_counters is required for these.
 */
int
xfs_mod_incore_sb_batch(
    struct xfs_mount    *mp,
    xfs_mod_sb_t        *msb,
    uint            nmsb,
    int         rsvd)
{
    xfs_mod_sb_t        *msbp;
    int         error = 0;

    /*
     * Loop through the array of mod structures and apply each individually.
     * If any fail, then back out all those which have already been applied.
     * Do all of this within the scope of the m_sb_lock so that all of the
     * changes will be atomic.
     */
    spin_lock(&mp->m_sb_lock);
    for (msbp = msb; msbp < (msb + nmsb); msbp++) {
        ASSERT(msbp->msb_field < XFS_SBS_ICOUNT ||
               msbp->msb_field > XFS_SBS_FDBLOCKS);

        error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
                           msbp->msb_delta, rsvd);
        if (error)
            goto unwind;
    }
    spin_unlock(&mp->m_sb_lock);
    return 0;

unwind:
    while (--msbp >= msb) {
        error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
                           -msbp->msb_delta, rsvd);
        ASSERT(error == 0);
    }
    spin_unlock(&mp->m_sb_lock);
    return error;
}

/*
 * xfs_getsb() is called to obtain the buffer for the superblock.
 * The buffer is returned locked and read in from disk.
 * The buffer should be released with a call to xfs_brelse().
 *
 * If the flags parameter is BUF_TRYLOCK, then we'll only return
 * the superblock buffer if it can be locked without sleeping.
 * If it can't then we'll return NULL.
 */
struct xfs_buf *
xfs_getsb(
    struct xfs_mount    *mp,
    int         flags)
{
    struct xfs_buf      *bp = mp->m_sb_bp;

    if (!xfs_buf_trylock(bp)) {
        if (flags & XBF_TRYLOCK)
            return NULL;
        xfs_buf_lock(bp);
    }

    xfs_buf_hold(bp);
    ASSERT(XFS_BUF_ISDONE(bp));
    return bp;
}

/*
 * Used to free the superblock along various error paths.
 */
void
xfs_freesb(
    struct xfs_mount    *mp)
{
    struct xfs_buf      *bp = mp->m_sb_bp;

    xfs_buf_lock(bp);
    mp->m_sb_bp = NULL;
    xfs_buf_relse(bp);
}

/*
 * Used to log changes to the superblock unit and width fields which could
 * be altered by the mount options, as well as any potential sb_features2
 * fixup. Only the first superblock is updated.
 */
int
xfs_mount_log_sb(
    xfs_mount_t *mp,
    __int64_t   fields)
{
    xfs_trans_t *tp;
    int     error;

    ASSERT(fields & (XFS_SB_UNIT | XFS_SB_WIDTH | XFS_SB_UUID |
             XFS_SB_FEATURES2 | XFS_SB_BAD_FEATURES2 |
             XFS_SB_VERSIONNUM));

    tp = xfs_trans_alloc(mp, XFS_TRANS_SB_UNIT);
    error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
                XFS_DEFAULT_LOG_COUNT);
    if (error) {
        xfs_trans_cancel(tp, 0);
        return error;
    }
    xfs_mod_sb(tp, fields);
    error = xfs_trans_commit(tp, 0);
    return error;
}

/*
 * If the underlying (data/log/rt) device is readonly, there are some
 * operations that cannot proceed.
 */
int
xfs_dev_is_read_only(
    struct xfs_mount    *mp,
    char            *message)
{
    if (xfs_readonly_buftarg(mp->m_ddev_targp) ||
        xfs_readonly_buftarg(mp->m_logdev_targp) ||
        (mp->m_rtdev_targp && xfs_readonly_buftarg(mp->m_rtdev_targp))) {
        xfs_notice(mp, "%s required on read-only device.", message);
        xfs_notice(mp, "write access unavailable, cannot proceed.");
        return EROFS;
    }
    return 0;
}

#ifdef HAVE_PERCPU_SB
/*
 * Per-cpu incore superblock counters
 *
 * Simple concept, difficult implementation
 *
 * Basically, replace the incore superblock counters with a distributed per cpu
 * counter for contended fields (e.g.  free block count).
 *
 * Difficulties arise in that the incore sb is used for ENOSPC checking, and
 * hence needs to be accurately read when we are running low on space. Hence
 * there is a method to enable and disable the per-cpu counters based on how
 * much "stuff" is available in them.
 *
 * Basically, a counter is enabled if there is enough free resource to justify
 * running a per-cpu fast-path. If the per-cpu counter runs out (i.e. a local
 * ENOSPC), then we disable the counters to synchronise all callers and
 * re-distribute the available resources.
 *
 * If, once we redistributed the available resources, we still get a failure,
 * we disable the per-cpu counter and go through the slow path.
 *
 * The slow path is the current xfs_mod_incore_sb() function.  This means that
 * when we disable a per-cpu counter, we need to drain its resources back to
 * the global superblock. We do this after disabling the counter to prevent
 * more threads from queueing up on the counter.
 *
 * Essentially, this means that we still need a lock in the fast path to enable
 * synchronisation between the global counters and the per-cpu counters. This
 * is not a problem because the lock will be local to a CPU almost all the time
 * and have little contention except when we get to ENOSPC conditions.
 *
 * Basically, this lock becomes a barrier that enables us to lock out the fast
 * path while we do things like enabling and disabling counters and
 * synchronising the counters.
 *
 * Locking rules:
 *
 *  1. m_sb_lock before picking up per-cpu locks
 *  2. per-cpu locks always picked up via for_each_online_cpu() order
 *  3. accurate counter sync requires m_sb_lock + per cpu locks
 *  4. modifying per-cpu counters requires holding per-cpu lock
 *  5. modifying global counters requires holding m_sb_lock
 *  6. enabling or disabling a counter requires holding the m_sb_lock 
 *     and _none_ of the per-cpu locks.
 *
 * Disabled counters are only ever re-enabled by a balance operation
 * that results in more free resources per CPU than a given threshold.
 * To ensure counters don't remain disabled, they are rebalanced when
 * the global resource goes above a higher threshold (i.e. some hysteresis
 * is present to prevent thrashing).
 */

#ifdef CONFIG_HOTPLUG_CPU
/*
 * hot-plug CPU notifier support.
 *
 * We need a notifier per filesystem as we need to be able to identify
 * the filesystem to balance the counters out. This is achieved by
 * having a notifier block embedded in the xfs_mount_t and doing pointer
 * magic to get the mount pointer from the notifier block address.
 */
STATIC int
xfs_icsb_cpu_notify(
    struct notifier_block *nfb,
    unsigned long action,
    void *hcpu)
{
    xfs_icsb_cnts_t *cntp;
    xfs_mount_t *mp;

    mp = (xfs_mount_t *)container_of(nfb, xfs_mount_t, m_icsb_notifier);
    cntp = (xfs_icsb_cnts_t *)
            per_cpu_ptr(mp->m_sb_cnts, (unsigned long)hcpu);
    switch (action) {
    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
        /* Easy Case - initialize the area and locks, and
         * then rebalance when online does everything else for us. */
        memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
        break;
    case CPU_ONLINE:
    case CPU_ONLINE_FROZEN:
        xfs_icsb_lock(mp);
        xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0);
        xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
        xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
        xfs_icsb_unlock(mp);
        break;
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        /* Disable all the counters, then fold the dead cpu's
         * count into the total on the global superblock and
         * re-enable the counters. */
        xfs_icsb_lock(mp);
        spin_lock(&mp->m_sb_lock);
        xfs_icsb_disable_counter(mp, XFS_SBS_ICOUNT);
        xfs_icsb_disable_counter(mp, XFS_SBS_IFREE);
        xfs_icsb_disable_counter(mp, XFS_SBS_FDBLOCKS);

        mp->m_sb.sb_icount += cntp->icsb_icount;
        mp->m_sb.sb_ifree += cntp->icsb_ifree;
        mp->m_sb.sb_fdblocks += cntp->icsb_fdblocks;

        memset(cntp, 0, sizeof(xfs_icsb_cnts_t));

        xfs_icsb_balance_counter_locked(mp, XFS_SBS_ICOUNT, 0);
        xfs_icsb_balance_counter_locked(mp, XFS_SBS_IFREE, 0);
        xfs_icsb_balance_counter_locked(mp, XFS_SBS_FDBLOCKS, 0);
        spin_unlock(&mp->m_sb_lock);
        xfs_icsb_unlock(mp);
        break;
    }

    return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */

int
xfs_icsb_init_counters(
    xfs_mount_t *mp)
{
    xfs_icsb_cnts_t *cntp;
    int     i;

    mp->m_sb_cnts = alloc_percpu(xfs_icsb_cnts_t);
    if (mp->m_sb_cnts == NULL)
        return -ENOMEM;

#ifdef CONFIG_HOTPLUG_CPU
    mp->m_icsb_notifier.notifier_call = xfs_icsb_cpu_notify;
    mp->m_icsb_notifier.priority = 0;
    register_hotcpu_notifier(&mp->m_icsb_notifier);
#endif /* CONFIG_HOTPLUG_CPU */

    for_each_online_cpu(i) {
        cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
        memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
    }

    mutex_init(&mp->m_icsb_mutex);

    /*
     * start with all counters disabled so that the
     * initial balance kicks us off correctly
     */
    mp->m_icsb_counters = -1;
    return 0;
}

void
xfs_icsb_reinit_counters(
    xfs_mount_t *mp)
{
    xfs_icsb_lock(mp);
    /*
     * start with all counters disabled so that the
     * initial balance kicks us off correctly
     */
    mp->m_icsb_counters = -1;
    xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0);
    xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
    xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
    xfs_icsb_unlock(mp);
}

void
xfs_icsb_destroy_counters(
    xfs_mount_t *mp)
{
    if (mp->m_sb_cnts) {
        unregister_hotcpu_notifier(&mp->m_icsb_notifier);
        free_percpu(mp->m_sb_cnts);
    }
    mutex_destroy(&mp->m_icsb_mutex);
}

STATIC void
xfs_icsb_lock_cntr(
    xfs_icsb_cnts_t *icsbp)
{
    while (test_and_set_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags)) {
        ndelay(1000);
    }
}

STATIC void
xfs_icsb_unlock_cntr(
    xfs_icsb_cnts_t *icsbp)
{
    clear_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags);
}


STATIC void
xfs_icsb_lock_all_counters(
    xfs_mount_t *mp)
{
    xfs_icsb_cnts_t *cntp;
    int     i;

    for_each_online_cpu(i) {
        cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
        xfs_icsb_lock_cntr(cntp);
    }
}

STATIC void
xfs_icsb_unlock_all_counters(
    xfs_mount_t *mp)
{
    xfs_icsb_cnts_t *cntp;
    int     i;

    for_each_online_cpu(i) {
        cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
        xfs_icsb_unlock_cntr(cntp);
    }
}

STATIC void
xfs_icsb_count(
    xfs_mount_t *mp,
    xfs_icsb_cnts_t *cnt,
    int     flags)
{
    xfs_icsb_cnts_t *cntp;
    int     i;

    memset(cnt, 0, sizeof(xfs_icsb_cnts_t));

    if (!(flags & XFS_ICSB_LAZY_COUNT))
        xfs_icsb_lock_all_counters(mp);

    for_each_online_cpu(i) {
        cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
        cnt->icsb_icount += cntp->icsb_icount;
        cnt->icsb_ifree += cntp->icsb_ifree;
        cnt->icsb_fdblocks += cntp->icsb_fdblocks;
    }

    if (!(flags & XFS_ICSB_LAZY_COUNT))
        xfs_icsb_unlock_all_counters(mp);
}

STATIC int
xfs_icsb_counter_disabled(
    xfs_mount_t *mp,
    xfs_sb_field_t  field)
{
    ASSERT((field >= XFS_SBS_ICOUNT) && (field <= XFS_SBS_FDBLOCKS));
    return test_bit(field, &mp->m_icsb_counters);
}

STATIC void
xfs_icsb_disable_counter(
    xfs_mount_t *mp,
    xfs_sb_field_t  field)
{
    xfs_icsb_cnts_t cnt;

    ASSERT((field >= XFS_SBS_ICOUNT) && (field <= XFS_SBS_FDBLOCKS));

    /*
     * If we are already disabled, then there is nothing to do
     * here. We check before locking all the counters to avoid
     * the expensive lock operation when being called in the
     * slow path and the counter is already disabled. This is
     * safe because the only time we set or clear this state is under
     * the m_icsb_mutex.
     */
    if (xfs_icsb_counter_disabled(mp, field))
        return;

    xfs_icsb_lock_all_counters(mp);
    if (!test_and_set_bit(field, &mp->m_icsb_counters)) {
        /* drain back to superblock */

        xfs_icsb_count(mp, &cnt, XFS_ICSB_LAZY_COUNT);
        switch(field) {
        case XFS_SBS_ICOUNT:
            mp->m_sb.sb_icount = cnt.icsb_icount;
            break;
        case XFS_SBS_IFREE:
            mp->m_sb.sb_ifree = cnt.icsb_ifree;
            break;
        case XFS_SBS_FDBLOCKS:
            mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
            break;
        default:
            BUG();
        }
    }

    xfs_icsb_unlock_all_counters(mp);
}

STATIC void
xfs_icsb_enable_counter(
    xfs_mount_t *mp,
    xfs_sb_field_t  field,
    uint64_t    count,
    uint64_t    resid)
{
    xfs_icsb_cnts_t *cntp;
    int     i;

    ASSERT((field >= XFS_SBS_ICOUNT) && (field <= XFS_SBS_FDBLOCKS));

    xfs_icsb_lock_all_counters(mp);
    for_each_online_cpu(i) {
        cntp = per_cpu_ptr(mp->m_sb_cnts, i);
        switch (field) {
        case XFS_SBS_ICOUNT:
            cntp->icsb_icount = count + resid;
            break;
        case XFS_SBS_IFREE:
            cntp->icsb_ifree = count + resid;
            break;
        case XFS_SBS_FDBLOCKS:
            cntp->icsb_fdblocks = count + resid;
            break;
        default:
            BUG();
            break;
        }
        resid = 0;
    }
    clear_bit(field, &mp->m_icsb_counters);
    xfs_icsb_unlock_all_counters(mp);
}

void
xfs_icsb_sync_counters_locked(
    xfs_mount_t *mp,
    int     flags)
{
    xfs_icsb_cnts_t cnt;

    xfs_icsb_count(mp, &cnt, flags);

    if (!xfs_icsb_counter_disabled(mp, XFS_SBS_ICOUNT))
        mp->m_sb.sb_icount = cnt.icsb_icount;
    if (!xfs_icsb_counter_disabled(mp, XFS_SBS_IFREE))
        mp->m_sb.sb_ifree = cnt.icsb_ifree;
    if (!xfs_icsb_counter_disabled(mp, XFS_SBS_FDBLOCKS))
        mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
}

/*
 * Accurate update of per-cpu counters to incore superblock
 */
void
xfs_icsb_sync_counters(
    xfs_mount_t *mp,
    int     flags)
{
    spin_lock(&mp->m_sb_lock);
    xfs_icsb_sync_counters_locked(mp, flags);
    spin_unlock(&mp->m_sb_lock);
}

/*
 * Balance and enable/disable counters as necessary.
 *
 * Thresholds for re-enabling counters are somewhat magic.  inode counts are
 * chosen to be the same number as single on disk allocation chunk per CPU, and
 * free blocks is something far enough zero that we aren't going thrash when we
 * get near ENOSPC. We also need to supply a minimum we require per cpu to
 * prevent looping endlessly when xfs_alloc_space asks for more than will
 * be distributed to a single CPU but each CPU has enough blocks to be
 * reenabled.
 *
 * Note that we can be called when counters are already disabled.
 * xfs_icsb_disable_counter() optimises the counter locking in this case to
 * prevent locking every per-cpu counter needlessly.
 */

#define XFS_ICSB_INO_CNTR_REENABLE  (uint64_t)64
#define XFS_ICSB_FDBLK_CNTR_REENABLE(mp) \
        (uint64_t)(512 + XFS_ALLOC_SET_ASIDE(mp))
STATIC void
xfs_icsb_balance_counter_locked(
    xfs_mount_t *mp,
    xfs_sb_field_t  field,
    int     min_per_cpu)
{
    uint64_t    count, resid;
    int     weight = num_online_cpus();
    uint64_t    min = (uint64_t)min_per_cpu;

    /* disable counter and sync counter */
    xfs_icsb_disable_counter(mp, field);

    /* update counters  - first CPU gets residual*/
    switch (field) {
    case XFS_SBS_ICOUNT:
        count = mp->m_sb.sb_icount;
        resid = do_div(count, weight);
        if (count < max(min, XFS_ICSB_INO_CNTR_REENABLE))
            return;
        break;
    case XFS_SBS_IFREE:
        count = mp->m_sb.sb_ifree;
        resid = do_div(count, weight);
        if (count < max(min, XFS_ICSB_INO_CNTR_REENABLE))
            return;
        break;
    case XFS_SBS_FDBLOCKS:
        count = mp->m_sb.sb_fdblocks;
        resid = do_div(count, weight);
        if (count < max(min, XFS_ICSB_FDBLK_CNTR_REENABLE(mp)))
            return;
        break;
    default:
        BUG();
        count = resid = 0;  /* quiet, gcc */
        break;
    }

    xfs_icsb_enable_counter(mp, field, count, resid);
}

STATIC void
xfs_icsb_balance_counter(
    xfs_mount_t *mp,
    xfs_sb_field_t  fields,
    int     min_per_cpu)
{
    spin_lock(&mp->m_sb_lock);
    xfs_icsb_balance_counter_locked(mp, fields, min_per_cpu);
    spin_unlock(&mp->m_sb_lock);
}

int
xfs_icsb_modify_counters(
    xfs_mount_t *mp,
    xfs_sb_field_t  field,
    int64_t     delta,
    int     rsvd)
{
    xfs_icsb_cnts_t *icsbp;
    long long   lcounter;   /* long counter for 64 bit fields */
    int     ret = 0;

    might_sleep();
again:
    preempt_disable();
    icsbp = this_cpu_ptr(mp->m_sb_cnts);

    /*
     * if the counter is disabled, go to slow path
     */
    if (unlikely(xfs_icsb_counter_disabled(mp, field)))
        goto slow_path;
    xfs_icsb_lock_cntr(icsbp);
    if (unlikely(xfs_icsb_counter_disabled(mp, field))) {
        xfs_icsb_unlock_cntr(icsbp);
        goto slow_path;
    }

    switch (field) {
    case XFS_SBS_ICOUNT:
        lcounter = icsbp->icsb_icount;
        lcounter += delta;
        if (unlikely(lcounter < 0))
            goto balance_counter;
        icsbp->icsb_icount = lcounter;
        break;

    case XFS_SBS_IFREE:
        lcounter = icsbp->icsb_ifree;
        lcounter += delta;
        if (unlikely(lcounter < 0))
            goto balance_counter;
        icsbp->icsb_ifree = lcounter;
        break;

    case XFS_SBS_FDBLOCKS:
        BUG_ON((mp->m_resblks - mp->m_resblks_avail) != 0);

        lcounter = icsbp->icsb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
        lcounter += delta;
        if (unlikely(lcounter < 0))
            goto balance_counter;
        icsbp->icsb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
        break;
    default:
        BUG();
        break;
    }
    xfs_icsb_unlock_cntr(icsbp);
    preempt_enable();
    return 0;

slow_path:
    preempt_enable();

    /*
     * serialise with a mutex so we don't burn lots of cpu on
     * the superblock lock. We still need to hold the superblock
     * lock, however, when we modify the global structures.
     */
    xfs_icsb_lock(mp);

    /*
     * Now running atomically.
     *
     * If the counter is enabled, someone has beaten us to rebalancing.
     * Drop the lock and try again in the fast path....
     */
    if (!(xfs_icsb_counter_disabled(mp, field))) {
        xfs_icsb_unlock(mp);
        goto again;
    }

    /*
     * The counter is currently disabled. Because we are
     * running atomically here, we know a rebalance cannot
     * be in progress. Hence we can go straight to operating
     * on the global superblock. We do not call xfs_mod_incore_sb()
     * here even though we need to get the m_sb_lock. Doing so
     * will cause us to re-enter this function and deadlock.
     * Hence we get the m_sb_lock ourselves and then call
     * xfs_mod_incore_sb_unlocked() as the unlocked path operates
     * directly on the global counters.
     */
    spin_lock(&mp->m_sb_lock);
    ret = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd);
    spin_unlock(&mp->m_sb_lock);

    /*
     * Now that we've modified the global superblock, we
     * may be able to re-enable the distributed counters
     * (e.g. lots of space just got freed). After that
     * we are done.
     */
    if (ret != ENOSPC)
        xfs_icsb_balance_counter(mp, field, 0);
    xfs_icsb_unlock(mp);
    return ret;

balance_counter:
    xfs_icsb_unlock_cntr(icsbp);
    preempt_enable();

    /*
     * We may have multiple threads here if multiple per-cpu
     * counters run dry at the same time. This will mean we can
     * do more balances than strictly necessary but it is not
     * the common slowpath case.
     */
    xfs_icsb_lock(mp);

    /*
     * running atomically.
     *
     * This will leave the counter in the correct state for future
     * accesses. After the rebalance, we simply try again and our retry
     * will either succeed through the fast path or slow path without
     * another balance operation being required.
     */
    xfs_icsb_balance_counter(mp, field, delta);
    xfs_icsb_unlock(mp);
    goto again;
}

#endif