Merge branch 'for-rmk' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux...

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / xfs / xfs_fsops.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_types.h"
#include "xfs_bit.h"
#include "xfs_inum.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_btree.h"
#include "xfs_error.h"
#include "xfs_alloc.h"
#include "xfs_ialloc.h"
#include "xfs_fsops.h"
#include "xfs_itable.h"
#include "xfs_trans_space.h"
#include "xfs_rtalloc.h"
#include "xfs_rw.h"
#include "xfs_filestream.h"
#include "xfs_trace.h"

/*
 * File system operations
 */

int
xfs_fs_geometry(
        xfs_mount_t             *mp,
        xfs_fsop_geom_t         *geo,
        int                     new_version)
{
        geo->blocksize = mp->m_sb.sb_blocksize;
        geo->rtextsize = mp->m_sb.sb_rextsize;
        geo->agblocks = mp->m_sb.sb_agblocks;
        geo->agcount = mp->m_sb.sb_agcount;
        geo->logblocks = mp->m_sb.sb_logblocks;
        geo->sectsize = mp->m_sb.sb_sectsize;
        geo->inodesize = mp->m_sb.sb_inodesize;
        geo->imaxpct = mp->m_sb.sb_imax_pct;
        geo->datablocks = mp->m_sb.sb_dblocks;
        geo->rtblocks = mp->m_sb.sb_rblocks;
        geo->rtextents = mp->m_sb.sb_rextents;
        geo->logstart = mp->m_sb.sb_logstart;
        ASSERT(sizeof(geo->uuid)==sizeof(mp->m_sb.sb_uuid));
        memcpy(geo->uuid, &mp->m_sb.sb_uuid, sizeof(mp->m_sb.sb_uuid));
        if (new_version >= 2) {
                geo->sunit = mp->m_sb.sb_unit;
                geo->swidth = mp->m_sb.sb_width;
        }
        if (new_version >= 3) {
                geo->version = XFS_FSOP_GEOM_VERSION;
                geo->flags =
                        (xfs_sb_version_hasattr(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_ATTR : 0) |
                        (xfs_sb_version_hasnlink(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_NLINK : 0) |
                        (xfs_sb_version_hasquota(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_QUOTA : 0) |
                        (xfs_sb_version_hasalign(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_IALIGN : 0) |
                        (xfs_sb_version_hasdalign(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_DALIGN : 0) |
                        (xfs_sb_version_hasshared(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_SHARED : 0) |
                        (xfs_sb_version_hasextflgbit(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_EXTFLG : 0) |
                        (xfs_sb_version_hasdirv2(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_DIRV2 : 0) |
                        (xfs_sb_version_hassector(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_SECTOR : 0) |
                        (xfs_sb_version_hasasciici(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_DIRV2CI : 0) |
                        (xfs_sb_version_haslazysbcount(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_LAZYSB : 0) |
                        (xfs_sb_version_hasattr2(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_ATTR2 : 0);
                geo->logsectsize = xfs_sb_version_hassector(&mp->m_sb) ?
                                mp->m_sb.sb_logsectsize : BBSIZE;
                geo->rtsectsize = mp->m_sb.sb_blocksize;
                geo->dirblocksize = mp->m_dirblksize;
        }
        if (new_version >= 4) {
                geo->flags |=
                        (xfs_sb_version_haslogv2(&mp->m_sb) ?
                                XFS_FSOP_GEOM_FLAGS_LOGV2 : 0);
                geo->logsunit = mp->m_sb.sb_logsunit;
        }
        return 0;
}

static int
xfs_growfs_data_private(
        xfs_mount_t             *mp,            /* mount point for filesystem */
        xfs_growfs_data_t       *in)            /* growfs data input struct */
{
        xfs_agf_t               *agf;
        xfs_agi_t               *agi;
        xfs_agnumber_t          agno;
        xfs_extlen_t            agsize;
        xfs_extlen_t            tmpsize;
        xfs_alloc_rec_t         *arec;
        struct xfs_btree_block  *block;
        xfs_buf_t               *bp;
        int                     bucket;
        int                     dpct;
        int                     error;
        xfs_agnumber_t          nagcount;
        xfs_agnumber_t          nagimax = 0;
        xfs_rfsblock_t          nb, nb_mod;
        xfs_rfsblock_t          new;
        xfs_rfsblock_t          nfree;
        xfs_agnumber_t          oagcount;
        int                     pct;
        xfs_trans_t             *tp;

        nb = in->newblocks;
        pct = in->imaxpct;
        if (nb < mp->m_sb.sb_dblocks || pct < 0 || pct > 100)
                return XFS_ERROR(EINVAL);
        if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
                return error;
        dpct = pct - mp->m_sb.sb_imax_pct;
        bp = xfs_buf_read_uncached(mp, mp->m_ddev_targp,
                                XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
                                BBTOB(XFS_FSS_TO_BB(mp, 1)), 0);
        if (!bp)
                return EIO;
        xfs_buf_relse(bp);

        new = nb;       /* use new as a temporary here */
        nb_mod = do_div(new, mp->m_sb.sb_agblocks);
        nagcount = new + (nb_mod != 0);
        if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) {
                nagcount--;
                nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks;
                if (nb < mp->m_sb.sb_dblocks)
                        return XFS_ERROR(EINVAL);
        }
        new = nb - mp->m_sb.sb_dblocks;
        oagcount = mp->m_sb.sb_agcount;

        /* allocate the new per-ag structures */
        if (nagcount > oagcount) {
                error = xfs_initialize_perag(mp, nagcount, &nagimax);
                if (error)
                        return error;
        }

        tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFS);
        tp->t_flags |= XFS_TRANS_RESERVE;
        if ((error = xfs_trans_reserve(tp, XFS_GROWFS_SPACE_RES(mp),
                        XFS_GROWDATA_LOG_RES(mp), 0, 0, 0))) {
                xfs_trans_cancel(tp, 0);
                return error;
        }

        /*
         * Write new AG headers to disk. Non-transactional, but written
         * synchronously so they are completed prior to the growfs transaction
         * being logged.
         */
        nfree = 0;
        for (agno = nagcount - 1; agno >= oagcount; agno--, new -= agsize) {
                /*
                 * AG freelist header block
                 */
                bp = xfs_buf_get(mp->m_ddev_targp,
                                 XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
                                 XFS_FSS_TO_BB(mp, 1), XBF_LOCK | XBF_MAPPED);
                agf = XFS_BUF_TO_AGF(bp);
                memset(agf, 0, mp->m_sb.sb_sectsize);
                agf->agf_magicnum = cpu_to_be32(XFS_AGF_MAGIC);
                agf->agf_versionnum = cpu_to_be32(XFS_AGF_VERSION);
                agf->agf_seqno = cpu_to_be32(agno);
                if (agno == nagcount - 1)
                        agsize =
                                nb -
                                (agno * (xfs_rfsblock_t)mp->m_sb.sb_agblocks);
                else
                        agsize = mp->m_sb.sb_agblocks;
                agf->agf_length = cpu_to_be32(agsize);
                agf->agf_roots[XFS_BTNUM_BNOi] = cpu_to_be32(XFS_BNO_BLOCK(mp));
                agf->agf_roots[XFS_BTNUM_CNTi] = cpu_to_be32(XFS_CNT_BLOCK(mp));
                agf->agf_levels[XFS_BTNUM_BNOi] = cpu_to_be32(1);
                agf->agf_levels[XFS_BTNUM_CNTi] = cpu_to_be32(1);
                agf->agf_flfirst = 0;
                agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
                agf->agf_flcount = 0;
                tmpsize = agsize - XFS_PREALLOC_BLOCKS(mp);
                agf->agf_freeblks = cpu_to_be32(tmpsize);
                agf->agf_longest = cpu_to_be32(tmpsize);
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
                }
                /*
                 * AG inode header block
                 */
                bp = xfs_buf_get(mp->m_ddev_targp,
                                 XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
                                 XFS_FSS_TO_BB(mp, 1), XBF_LOCK | XBF_MAPPED);
                agi = XFS_BUF_TO_AGI(bp);
                memset(agi, 0, mp->m_sb.sb_sectsize);
                agi->agi_magicnum = cpu_to_be32(XFS_AGI_MAGIC);
                agi->agi_versionnum = cpu_to_be32(XFS_AGI_VERSION);
                agi->agi_seqno = cpu_to_be32(agno);
                agi->agi_length = cpu_to_be32(agsize);
                agi->agi_count = 0;
                agi->agi_root = cpu_to_be32(XFS_IBT_BLOCK(mp));
                agi->agi_level = cpu_to_be32(1);
                agi->agi_freecount = 0;
                agi->agi_newino = cpu_to_be32(NULLAGINO);
                agi->agi_dirino = cpu_to_be32(NULLAGINO);
                for (bucket = 0; bucket < XFS_AGI_UNLINKED_BUCKETS; bucket++)
                        agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
                }
                /*
                 * BNO btree root block
                 */
                bp = xfs_buf_get(mp->m_ddev_targp,
                                 XFS_AGB_TO_DADDR(mp, agno, XFS_BNO_BLOCK(mp)),
                                 BTOBB(mp->m_sb.sb_blocksize),
                                 XBF_LOCK | XBF_MAPPED);
                block = XFS_BUF_TO_BLOCK(bp);
                memset(block, 0, mp->m_sb.sb_blocksize);
                block->bb_magic = cpu_to_be32(XFS_ABTB_MAGIC);
                block->bb_level = 0;
                block->bb_numrecs = cpu_to_be16(1);
                block->bb_u.s.bb_leftsib = cpu_to_be32(NULLAGBLOCK);
                block->bb_u.s.bb_rightsib = cpu_to_be32(NULLAGBLOCK);
                arec = XFS_ALLOC_REC_ADDR(mp, block, 1);
                arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
                arec->ar_blockcount = cpu_to_be32(
                        agsize - be32_to_cpu(arec->ar_startblock));
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
                }
                /*
                 * CNT btree root block
                 */
                bp = xfs_buf_get(mp->m_ddev_targp,
                                 XFS_AGB_TO_DADDR(mp, agno, XFS_CNT_BLOCK(mp)),
                                 BTOBB(mp->m_sb.sb_blocksize),
                                 XBF_LOCK | XBF_MAPPED);
                block = XFS_BUF_TO_BLOCK(bp);
                memset(block, 0, mp->m_sb.sb_blocksize);
                block->bb_magic = cpu_to_be32(XFS_ABTC_MAGIC);
                block->bb_level = 0;
                block->bb_numrecs = cpu_to_be16(1);
                block->bb_u.s.bb_leftsib = cpu_to_be32(NULLAGBLOCK);
                block->bb_u.s.bb_rightsib = cpu_to_be32(NULLAGBLOCK);
                arec = XFS_ALLOC_REC_ADDR(mp, block, 1);
                arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
                arec->ar_blockcount = cpu_to_be32(
                        agsize - be32_to_cpu(arec->ar_startblock));
                nfree += be32_to_cpu(arec->ar_blockcount);
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
                }
                /*
                 * INO btree root block
                 */
                bp = xfs_buf_get(mp->m_ddev_targp,
                                 XFS_AGB_TO_DADDR(mp, agno, XFS_IBT_BLOCK(mp)),
                                 BTOBB(mp->m_sb.sb_blocksize),
                                 XBF_LOCK | XBF_MAPPED);
                block = XFS_BUF_TO_BLOCK(bp);
                memset(block, 0, mp->m_sb.sb_blocksize);
                block->bb_magic = cpu_to_be32(XFS_IBT_MAGIC);
                block->bb_level = 0;
                block->bb_numrecs = 0;
                block->bb_u.s.bb_leftsib = cpu_to_be32(NULLAGBLOCK);
                block->bb_u.s.bb_rightsib = cpu_to_be32(NULLAGBLOCK);
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
                }
        }
        xfs_trans_agblocks_delta(tp, nfree);
        /*
         * There are new blocks in the old last a.g.
         */
        if (new) {
                /*
                 * Change the agi length.
                 */
                error = xfs_ialloc_read_agi(mp, tp, agno, &bp);
                if (error) {
                        goto error0;
                }
                ASSERT(bp);
                agi = XFS_BUF_TO_AGI(bp);
                be32_add_cpu(&agi->agi_length, new);
                ASSERT(nagcount == oagcount ||
                       be32_to_cpu(agi->agi_length) == mp->m_sb.sb_agblocks);
                xfs_ialloc_log_agi(tp, bp, XFS_AGI_LENGTH);
                /*
                 * Change agf length.
                 */
                error = xfs_alloc_read_agf(mp, tp, agno, 0, &bp);
                if (error) {
                        goto error0;
                }
                ASSERT(bp);
                agf = XFS_BUF_TO_AGF(bp);
                be32_add_cpu(&agf->agf_length, new);
                ASSERT(be32_to_cpu(agf->agf_length) ==
                       be32_to_cpu(agi->agi_length));

                xfs_alloc_log_agf(tp, bp, XFS_AGF_LENGTH);
                /*
                 * Free the new space.
                 */
                error = xfs_free_extent(tp, XFS_AGB_TO_FSB(mp, agno,
                        be32_to_cpu(agf->agf_length) - new), new);
                if (error) {
                        goto error0;
                }
        }

        /*
         * Update changed superblock fields transactionally. These are not
         * seen by the rest of the world until the transaction commit applies
         * them atomically to the superblock.
         */
        if (nagcount > oagcount)
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount);
        if (nb > mp->m_sb.sb_dblocks)
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS,
                                 nb - mp->m_sb.sb_dblocks);
        if (nfree)
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, nfree);
        if (dpct)
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_IMAXPCT, dpct);
        error = xfs_trans_commit(tp, 0);
        if (error)
                return error;

        /* New allocation groups fully initialized, so update mount struct */
        if (nagimax)
                mp->m_maxagi = nagimax;
        if (mp->m_sb.sb_imax_pct) {
                __uint64_t icount = mp->m_sb.sb_dblocks * mp->m_sb.sb_imax_pct;
                do_div(icount, 100);
                mp->m_maxicount = icount << mp->m_sb.sb_inopblog;
        } else
                mp->m_maxicount = 0;
        xfs_set_low_space_thresholds(mp);

        /* update secondary superblocks. */
        for (agno = 1; agno < nagcount; agno++) {
                error = xfs_read_buf(mp, mp->m_ddev_targp,
                                  XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
                                  XFS_FSS_TO_BB(mp, 1), 0, &bp);
                if (error) {
                        xfs_fs_cmn_err(CE_WARN, mp,
                        "error %d reading secondary superblock for ag %d",
                                error, agno);
                        break;
                }
                xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, XFS_SB_ALL_BITS);
                /*
                 * If we get an error writing out the alternate superblocks,
                 * just issue a warning and continue.  The real work is
                 * already done and committed.
                 */
                if (!(error = xfs_bwrite(mp, bp))) {
                        continue;
                } else {
                        xfs_fs_cmn_err(CE_WARN, mp,
                "write error %d updating secondary superblock for ag %d",
                                error, agno);
                        break; /* no point in continuing */
                }
        }
        return 0;

 error0:
        xfs_trans_cancel(tp, XFS_TRANS_ABORT);
        return error;
}

static int
xfs_growfs_log_private(
        xfs_mount_t             *mp,    /* mount point for filesystem */
        xfs_growfs_log_t        *in)    /* growfs log input struct */
{
        xfs_extlen_t            nb;

        nb = in->newblocks;
        if (nb < XFS_MIN_LOG_BLOCKS || nb < XFS_B_TO_FSB(mp, XFS_MIN_LOG_BYTES))
                return XFS_ERROR(EINVAL);
        if (nb == mp->m_sb.sb_logblocks &&
            in->isint == (mp->m_sb.sb_logstart != 0))
                return XFS_ERROR(EINVAL);
        /*
         * Moving the log is hard, need new interfaces to sync
         * the log first, hold off all activity while moving it.
         * Can have shorter or longer log in the same space,
         * or transform internal to external log or vice versa.
         */
        return XFS_ERROR(ENOSYS);
}

/*
 * protected versions of growfs function acquire and release locks on the mount
 * point - exported through ioctls: XFS_IOC_FSGROWFSDATA, XFS_IOC_FSGROWFSLOG,
 * XFS_IOC_FSGROWFSRT
 */


int
xfs_growfs_data(
        xfs_mount_t             *mp,
        xfs_growfs_data_t       *in)
{
        int error;

        if (!capable(CAP_SYS_ADMIN))
                return XFS_ERROR(EPERM);
        if (!mutex_trylock(&mp->m_growlock))
                return XFS_ERROR(EWOULDBLOCK);
        error = xfs_growfs_data_private(mp, in);
        mutex_unlock(&mp->m_growlock);
        return error;
}

int
xfs_growfs_log(
        xfs_mount_t             *mp,
        xfs_growfs_log_t        *in)
{
        int error;

        if (!capable(CAP_SYS_ADMIN))
                return XFS_ERROR(EPERM);
        if (!mutex_trylock(&mp->m_growlock))
                return XFS_ERROR(EWOULDBLOCK);
        error = xfs_growfs_log_private(mp, in);
        mutex_unlock(&mp->m_growlock);
        return error;
}

/*
 * exported through ioctl XFS_IOC_FSCOUNTS
 */

int
xfs_fs_counts(
        xfs_mount_t             *mp,
        xfs_fsop_counts_t       *cnt)
{
        xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
        spin_lock(&mp->m_sb_lock);
        cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
        cnt->freertx = mp->m_sb.sb_frextents;
        cnt->freeino = mp->m_sb.sb_ifree;
        cnt->allocino = mp->m_sb.sb_icount;
        spin_unlock(&mp->m_sb_lock);
        return 0;
}

/*
 * exported through ioctl XFS_IOC_SET_RESBLKS & XFS_IOC_GET_RESBLKS
 *
 * xfs_reserve_blocks is called to set m_resblks
 * in the in-core mount table. The number of unused reserved blocks
 * is kept in m_resblks_avail.
 *
 * Reserve the requested number of blocks if available. Otherwise return
 * as many as possible to satisfy the request. The actual number
 * reserved are returned in outval
 *
 * A null inval pointer indicates that only the current reserved blocks
 * available  should  be returned no settings are changed.
 */

int
xfs_reserve_blocks(
        xfs_mount_t             *mp,
        __uint64_t              *inval,
        xfs_fsop_resblks_t      *outval)
{
        __int64_t               lcounter, delta, fdblks_delta;
        __uint64_t              request;

        /* If inval is null, report current values and return */
        if (inval == (__uint64_t *)NULL) {
                if (!outval)
                        return EINVAL;
                outval->resblks = mp->m_resblks;
                outval->resblks_avail = mp->m_resblks_avail;
                return 0;
        }

        request = *inval;

        /*
         * With per-cpu counters, this becomes an interesting
         * problem. we needto work out if we are freeing or allocation
         * blocks first, then we can do the modification as necessary.
         *
         * We do this under the m_sb_lock so that if we are near
         * ENOSPC, we will hold out any changes while we work out
         * what to do. This means that the amount of free space can
         * change while we do this, so we need to retry if we end up
         * trying to reserve more space than is available.
         *
         * We also use the xfs_mod_incore_sb() interface so that we
         * don't have to care about whether per cpu counter are
         * enabled, disabled or even compiled in....
         */
retry:
        spin_lock(&mp->m_sb_lock);
        xfs_icsb_sync_counters_locked(mp, 0);

        /*
         * If our previous reservation was larger than the current value,
         * then move any unused blocks back to the free pool.
         */
        fdblks_delta = 0;
        if (mp->m_resblks > request) {
                lcounter = mp->m_resblks_avail - request;
                if (lcounter  > 0) {            /* release unused blocks */
                        fdblks_delta = lcounter;
                        mp->m_resblks_avail -= lcounter;
                }
                mp->m_resblks = request;
        } else {
                __int64_t       free;

                free =  mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
                if (!free)
                        goto out; /* ENOSPC and fdblks_delta = 0 */

                delta = request - mp->m_resblks;
                lcounter = free - delta;
                if (lcounter < 0) {
                        /* We can't satisfy the request, just get what we can */
                        mp->m_resblks += free;
                        mp->m_resblks_avail += free;
                        fdblks_delta = -free;
                } else {
                        fdblks_delta = -delta;
                        mp->m_resblks = request;
                        mp->m_resblks_avail += delta;
                }
        }
out:
        if (outval) {
                outval->resblks = mp->m_resblks;
                outval->resblks_avail = mp->m_resblks_avail;
        }
        spin_unlock(&mp->m_sb_lock);

        if (fdblks_delta) {
                /*
                 * If we are putting blocks back here, m_resblks_avail is
                 * already at its max so this will put it in the free pool.
                 *
                 * If we need space, we'll either succeed in getting it
                 * from the free block count or we'll get an enospc. If
                 * we get a ENOSPC, it means things changed while we were
                 * calculating fdblks_delta and so we should try again to
                 * see if there is anything left to reserve.
                 *
                 * Don't set the reserved flag here - we don't want to reserve
                 * the extra reserve blocks from the reserve.....
                 */
                int error;
                error = xfs_icsb_modify_counters(mp, XFS_SBS_FDBLOCKS,
                                                 fdblks_delta, 0);
                if (error == ENOSPC)
                        goto retry;
        }
        return 0;
}

/*
 * Dump a transaction into the log that contains no real change. This is needed
 * to be able to make the log dirty or stamp the current tail LSN into the log
 * during the covering operation.
 *
 * We cannot use an inode here for this - that will push dirty state back up
 * into the VFS and then periodic inode flushing will prevent log covering from
 * making progress. Hence we log a field in the superblock instead.
 */
int
xfs_fs_log_dummy(
        xfs_mount_t     *mp,
        int             flags)
{
        xfs_trans_t     *tp;
        int             error;

        tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, 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;
        }

        /* log the UUID because it is an unchanging field */
        xfs_mod_sb(tp, XFS_SB_UUID);
        if (flags & SYNC_WAIT)
                xfs_trans_set_sync(tp);
        return xfs_trans_commit(tp, 0);
}

int
xfs_fs_goingdown(
        xfs_mount_t     *mp,
        __uint32_t      inflags)
{
        switch (inflags) {
        case XFS_FSOP_GOING_FLAGS_DEFAULT: {
                struct super_block *sb = freeze_bdev(mp->m_super->s_bdev);

                if (sb && !IS_ERR(sb)) {
                        xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
                        thaw_bdev(sb->s_bdev, sb);
                }

                break;
        }
        case XFS_FSOP_GOING_FLAGS_LOGFLUSH:
                xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
                break;
        case XFS_FSOP_GOING_FLAGS_NOLOGFLUSH:
                xfs_force_shutdown(mp,
                                SHUTDOWN_FORCE_UMOUNT | SHUTDOWN_LOG_IO_ERROR);
                break;
        default:
                return XFS_ERROR(EINVAL);
        }

        return 0;
}