timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING

[linux/fpc-iii.git] / fs / xfs / xfs_mount.c

/*
 * 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_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_inode.h"
#include "xfs_dir2.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_rtalloc.h"
#include "xfs_bmap.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_log.h"
#include "xfs_error.h"
#include "xfs_quota.h"
#include "xfs_fsops.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_sysfs.h"


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 -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 -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);
}


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);

        /* Limited by ULONG_MAX of page cache index */
        if (nblocks >> (PAGE_CACHE_SHIFT - sbp->sb_blocklog) > ULONG_MAX)
                return -EFBIG;
        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, agcount);
        else
                index = xfs_set_inode64(mp, agcount);

        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;
}

/*
 * xfs_readsb
 *
 * Does the initial read of the superblock.
 */
int
xfs_readsb(
        struct xfs_mount *mp,
        int             flags)
{
        unsigned int    sector_size;
        struct xfs_buf  *bp;
        struct xfs_sb   *sbp = &mp->m_sb;
        int             error;
        int             loud = !(flags & XFS_MFSI_QUIET);
        const struct xfs_buf_ops *buf_ops;

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

        /*
         * For the initial read, we must guess at the sector
         * size based on the block device.  It's enough to
         * get the sb_sectsize out of the superblock and
         * then reread with the proper length.
         * We don't verify it yet, because it may not be complete.
         */
        sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
        buf_ops = NULL;

        /*
         * Allocate a (locked) buffer to hold the superblock.
         * This will be kept around at all times to optimize
         * access to the superblock.
         */
reread:
        error = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
                                   BTOBB(sector_size), 0, &bp, buf_ops);
        if (error) {
                if (loud)
                        xfs_warn(mp, "SB validate failed with error %d.", error);
                /* bad CRC means corrupted metadata */
                if (error == -EFSBADCRC)
                        error = -EFSCORRUPTED;
                return error;
        }

        /*
         * Initialize the mount structure from the superblock.
         */
        xfs_sb_from_disk(sbp, XFS_BUF_TO_SBP(bp));

        /*
         * If we haven't validated the superblock, do so now before we try
         * to check the sector size and reread the superblock appropriately.
         */
        if (sbp->sb_magicnum != XFS_SB_MAGIC) {
                if (loud)
                        xfs_warn(mp, "Invalid superblock magic number");
                error = -EINVAL;
                goto release_buf;
        }

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

        if (buf_ops == NULL) {
                /*
                 * Re-read the superblock so the buffer is correctly sized,
                 * and properly verified.
                 */
                xfs_buf_relse(bp);
                sector_size = sbp->sb_sectsize;
                buf_ops = loud ? &xfs_sb_buf_ops : &xfs_sb_quiet_buf_ops;
                goto reread;
        }

        xfs_reinit_percpu_counters(mp);

        /* no need to be quiet anymore, so reset the buf ops */
        bp->b_ops = &xfs_sb_buf_ops;

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

release_buf:
        xfs_buf_relse(bp);
        return error;
}

/*
 * 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)) {
                        xfs_warn(mp,
                "alignment check failed: sunit/swidth vs. blocksize(%d)",
                                sbp->sb_blocksize);
                        return -EINVAL;
                } 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)) {
                                xfs_warn(mp,
                        "alignment check failed: sunit/swidth vs. agsize(%d)",
                                         sbp->sb_agblocks);
                                return -EINVAL;
                        } else if (mp->m_dalign) {
                                mp->m_swidth = XFS_BB_TO_FSBT(mp, mp->m_swidth);
                        } else {
                                xfs_warn(mp,
                        "alignment check failed: sunit(%d) less than bsize(%d)",
                                         mp->m_dalign, sbp->sb_blocksize);
                                return -EINVAL;
                        }
                }

                /*
                 * 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_sb = true;
                        }
                        if (sbp->sb_width != mp->m_swidth) {
                                sbp->sb_width = mp->m_swidth;
                                mp->m_update_sb = true;
                        }
                } else {
                        xfs_warn(mp,
        "cannot change alignment: superblock does not support data alignment");
                        return -EINVAL;
                }
        } 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) is an ok size.
 */
STATIC int
xfs_check_sizes(
        struct xfs_mount *mp)
{
        struct xfs_buf  *bp;
        xfs_daddr_t     d;
        int             error;

        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 -EFBIG;
        }
        error = xfs_buf_read_uncached(mp->m_ddev_targp,
                                        d - XFS_FSS_TO_BB(mp, 1),
                                        XFS_FSS_TO_BB(mp, 1), 0, &bp, NULL);
        if (error) {
                xfs_warn(mp, "last sector read failed");
                return error;
        }
        xfs_buf_relse(bp);

        if (mp->m_logdev_targp == mp->m_ddev_targp)
                return 0;

        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 -EFBIG;
        }
        error = xfs_buf_read_uncached(mp->m_logdev_targp,
                                        d - XFS_FSB_TO_BB(mp, 1),
                                        XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
        if (error) {
                xfs_warn(mp, "log device read failed");
                return error;
        }
        xfs_buf_relse(bp);
        return 0;
}

/*
 * Clear the quotaflags in memory and in the superblock.
 */
int
xfs_mount_reset_sbqflags(
        struct xfs_mount        *mp)
{
        mp->m_qflags = 0;

        /* It is OK to look at sb_qflags in the 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 (!xfs_fs_writable(mp, SB_FREEZE_WRITE))
                return 0;

        return xfs_sync_sb(mp, false);
}

__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_sb_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. The
         * superblock writeback code ensures the new sb_features2 is copied to
         * sb_bad_features2 before it is logged or written to disk.
         */
        if (xfs_sb_has_mismatched_features2(sbp)) {
                xfs_warn(mp, "correcting sb_features alignment problem");
                sbp->sb_features2 |= sbp->sb_bad_features2;
                mp->m_update_sb = true;

                /*
                 * 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_sb = true;

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

        /* always use v2 inodes by default now */
        if (!(mp->m_sb.sb_versionnum & XFS_SB_VERSION_NLINKBIT)) {
                mp->m_sb.sb_versionnum |= XFS_SB_VERSION_NLINKBIT;
                mp->m_update_sb = true;
        }

        /*
         * 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_sysfs_init(&mp->m_kobj, &xfs_mp_ktype, NULL, mp->m_fsname);
        if (error)
                goto out;

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

        /*
         * 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.
         *
         * For v5 filesystems, scale the cluster size with the inode size to
         * keep a constant ratio of inode per cluster buffer, but only if mkfs
         * has set the inode alignment value appropriately for larger cluster
         * sizes.
         */
        mp->m_inode_cluster_size = XFS_INODE_BIG_CLUSTER_SIZE;
        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                int     new_size = mp->m_inode_cluster_size;

                new_size *= mp->m_sb.sb_inodesize / XFS_DINODE_MIN_SIZE;
                if (mp->m_sb.sb_inoalignmt >= XFS_B_TO_FSBT(mp, new_size))
                        mp->m_inode_cluster_size = new_size;
        }

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

        /*
         * Check that the data (and log if separate) is 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 */

        error = xfs_da_mount(mp);
        if (error) {
                xfs_warn(mp, "Failed dir/attr init: %d", error);
                goto out_remove_uuid;
        }

        /*
         * 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_free_dir;
        }

        if (!sbp->sb_logblocks) {
                xfs_warn(mp, "no log defined");
                XFS_ERROR_REPORT("xfs_mountfs", XFS_ERRLEVEL_LOW, mp);
                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_log_dealloc;
        }

        /*
         * 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 = -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_sb && !(mp->m_flags & XFS_MOUNT_RDONLY)) {
                error = xfs_sync_sb(mp, false);
                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)
                                goto out_rtunmount;
                }
        }

        /*
         * 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_free_dir:
        xfs_da_unmount(mp);
 out_remove_uuid:
        xfs_uuid_unmount(mp);
 out_remove_sysfs:
        xfs_sysfs_del(&mp->m_kobj);
 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;

        cancel_delayed_work_sync(&mp->m_eofblocks_work);

        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
         * inodes and none should be pinned or locked, but use synchronous
         * reclaim just to be sure. We can stop background inode reclaim
         * here as well if it is still running.
         */
        cancel_delayed_work_sync(&mp->m_reclaim_work);
        xfs_reclaim_inodes(mp, SYNC_WAIT);

        xfs_qm_unmount(mp);

        /*
         * 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.");

        xfs_log_unmount(mp);
        xfs_da_unmount(mp);
        xfs_uuid_unmount(mp);

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

        xfs_sysfs_del(&mp->m_kobj);
}

/*
 * Determine whether modifications can proceed. The caller specifies the minimum
 * freeze level for which modifications should not be allowed. This allows
 * certain operations to proceed while the freeze sequence is in progress, if
 * necessary.
 */
bool
xfs_fs_writable(
        struct xfs_mount        *mp,
        int                     level)
{
        ASSERT(level > SB_UNFROZEN);
        if ((mp->m_super->s_writers.frozen >= level) ||
            XFS_FORCED_SHUTDOWN(mp) || (mp->m_flags & XFS_MOUNT_RDONLY))
                return false;

        return true;
}

/*
 * xfs_log_sbcount
 *
 * Sync the superblock counters to disk.
 *
 * Note this code can be called during the process of freezing, so we use the
 * transaction allocator that does not block when the transaction subsystem is
 * in its frozen state.
 */
int
xfs_log_sbcount(xfs_mount_t *mp)
{
        /* allow this to proceed during the freeze sequence... */
        if (!xfs_fs_writable(mp, SB_FREEZE_COMPLETE))
                return 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;

        return xfs_sync_sb(mp, true);
}

/*
 * Deltas for the inode count are +/-64, hence we use a large batch size
 * of 128 so we don't need to take the counter lock on every update.
 */
#define XFS_ICOUNT_BATCH        128
int
xfs_mod_icount(
        struct xfs_mount        *mp,
        int64_t                 delta)
{
        __percpu_counter_add(&mp->m_icount, delta, XFS_ICOUNT_BATCH);
        if (__percpu_counter_compare(&mp->m_icount, 0, XFS_ICOUNT_BATCH) < 0) {
                ASSERT(0);
                percpu_counter_add(&mp->m_icount, -delta);
                return -EINVAL;
        }
        return 0;
}

int
xfs_mod_ifree(
        struct xfs_mount        *mp,
        int64_t                 delta)
{
        percpu_counter_add(&mp->m_ifree, delta);
        if (percpu_counter_compare(&mp->m_ifree, 0) < 0) {
                ASSERT(0);
                percpu_counter_add(&mp->m_ifree, -delta);
                return -EINVAL;
        }
        return 0;
}

/*
 * Deltas for the block count can vary from 1 to very large, but lock contention
 * only occurs on frequent small block count updates such as in the delayed
 * allocation path for buffered writes (page a time updates). Hence we set
 * a large batch count (1024) to minimise global counter updates except when
 * we get near to ENOSPC and we have to be very accurate with our updates.
 */
#define XFS_FDBLOCKS_BATCH      1024
int
xfs_mod_fdblocks(
        struct xfs_mount        *mp,
        int64_t                 delta,
        bool                    rsvd)
{
        int64_t                 lcounter;
        long long               res_used;
        s32                     batch;

        if (delta > 0) {
                /*
                 * If the reserve pool is depleted, put blocks back into it
                 * first. Most of the time the pool is full.
                 */
                if (likely(mp->m_resblks == mp->m_resblks_avail)) {
                        percpu_counter_add(&mp->m_fdblocks, delta);
                        return 0;
                }

                spin_lock(&mp->m_sb_lock);
                res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);

                if (res_used > delta) {
                        mp->m_resblks_avail += delta;
                } else {
                        delta -= res_used;
                        mp->m_resblks_avail = mp->m_resblks;
                        percpu_counter_add(&mp->m_fdblocks, delta);
                }
                spin_unlock(&mp->m_sb_lock);
                return 0;
        }

        /*
         * Taking blocks away, need to be more accurate the closer we
         * are to zero.
         *
         * If the counter has a value of less than 2 * max batch size,
         * then make everything serialise as we are real close to
         * ENOSPC.
         */
        if (__percpu_counter_compare(&mp->m_fdblocks, 2 * XFS_FDBLOCKS_BATCH,
                                     XFS_FDBLOCKS_BATCH) < 0)
                batch = 1;
        else
                batch = XFS_FDBLOCKS_BATCH;

        __percpu_counter_add(&mp->m_fdblocks, delta, batch);
        if (__percpu_counter_compare(&mp->m_fdblocks, XFS_ALLOC_SET_ASIDE(mp),
                                     XFS_FDBLOCKS_BATCH) >= 0) {
                /* we had space! */
                return 0;
        }

        /*
         * lock up the sb for dipping into reserves before releasing the space
         * that took us to ENOSPC.
         */
        spin_lock(&mp->m_sb_lock);
        percpu_counter_add(&mp->m_fdblocks, -delta);
        if (!rsvd)
                goto fdblocks_enospc;

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

int
xfs_mod_frextents(
        struct xfs_mount        *mp,
        int64_t                 delta)
{
        int64_t                 lcounter;
        int                     ret = 0;

        spin_lock(&mp->m_sb_lock);
        lcounter = mp->m_sb.sb_frextents + delta;
        if (lcounter < 0)
                ret = -ENOSPC;
        else
                mp->m_sb.sb_frextents = lcounter;
        spin_unlock(&mp->m_sb_lock);
        return ret;
}

/*
 * 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);
}

/*
 * 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;
}