initial commit with v2.6.32.60

[linux-2.6.32.60-moxart.git] / fs / xfs / linux-2.6 / xfs_sync.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_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_inode.h"
#include "xfs_dinode.h"
#include "xfs_error.h"
#include "xfs_mru_cache.h"
#include "xfs_filestream.h"
#include "xfs_vnodeops.h"
#include "xfs_utils.h"
#include "xfs_buf_item.h"
#include "xfs_inode_item.h"
#include "xfs_rw.h"
#include "xfs_quota.h"

#include <linux/kthread.h>
#include <linux/freezer.h>


STATIC xfs_inode_t *
xfs_inode_ag_lookup(
        struct xfs_mount        *mp,
        struct xfs_perag        *pag,
        uint32_t                *first_index,
        int                     tag)
{
        int                     nr_found;
        struct xfs_inode        *ip;

        /*
         * use a gang lookup to find the next inode in the tree
         * as the tree is sparse and a gang lookup walks to find
         * the number of objects requested.
         */
        if (tag == XFS_ICI_NO_TAG) {
                nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,
                                (void **)&ip, *first_index, 1);
        } else {
                nr_found = radix_tree_gang_lookup_tag(&pag->pag_ici_root,
                                (void **)&ip, *first_index, 1, tag);
        }
        if (!nr_found)
                return NULL;

        /*
         * Update the index for the next lookup. Catch overflows
         * into the next AG range which can occur if we have inodes
         * in the last block of the AG and we are currently
         * pointing to the last inode.
         */
        *first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
        if (*first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
                return NULL;
        return ip;
}

STATIC int
xfs_inode_ag_walk(
        struct xfs_mount        *mp,
        xfs_agnumber_t          ag,
        int                     (*execute)(struct xfs_inode *ip,
                                           struct xfs_perag *pag, int flags),
        int                     flags,
        int                     tag,
        int                     exclusive,
        int                     *nr_to_scan)
{
        struct xfs_perag        *pag = &mp->m_perag[ag];
        uint32_t                first_index;
        int                     last_error = 0;
        int                     skipped;

restart:
        skipped = 0;
        first_index = 0;
        do {
                int             error = 0;
                xfs_inode_t     *ip;

                if (exclusive)
                        write_lock(&pag->pag_ici_lock);
                else
                        read_lock(&pag->pag_ici_lock);
                ip = xfs_inode_ag_lookup(mp, pag, &first_index, tag);
                if (!ip) {
                        if (exclusive)
                                write_unlock(&pag->pag_ici_lock);
                        else
                                read_unlock(&pag->pag_ici_lock);
                        break;
                }

                /* execute releases pag->pag_ici_lock */
                error = execute(ip, pag, flags);
                if (error == EAGAIN) {
                        skipped++;
                        continue;
                }
                if (error)
                        last_error = error;

                /* bail out if the filesystem is corrupted.  */
                if (error == EFSCORRUPTED)
                        break;

        } while ((*nr_to_scan)--);

        if (skipped) {
                delay(1);
                goto restart;
        }

        xfs_put_perag(mp, pag);
        return last_error;
}

int
xfs_inode_ag_iterator(
        struct xfs_mount        *mp,
        int                     (*execute)(struct xfs_inode *ip,
                                           struct xfs_perag *pag, int flags),
        int                     flags,
        int                     tag,
        int                     exclusive,
        int                     *nr_to_scan)
{
        int                     error = 0;
        int                     last_error = 0;
        xfs_agnumber_t          ag;
        int                     nr;

        nr = nr_to_scan ? *nr_to_scan : INT_MAX;
        for (ag = 0; ag < mp->m_sb.sb_agcount; ag++) {
                if (!mp->m_perag[ag].pag_ici_init)
                        continue;
                error = xfs_inode_ag_walk(mp, ag, execute, flags, tag,
                                                exclusive, &nr);
                if (error) {
                        last_error = error;
                        if (error == EFSCORRUPTED)
                                break;
                }
                if (nr <= 0)
                        break;
        }
        if (nr_to_scan)
                *nr_to_scan = nr;
        return XFS_ERROR(last_error);
}

/* must be called with pag_ici_lock held and releases it */
int
xfs_sync_inode_valid(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag)
{
        struct inode            *inode = VFS_I(ip);
        int                     error = EFSCORRUPTED;

        /* nothing to sync during shutdown */
        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                goto out_unlock;

        /* avoid new or reclaimable inodes. Leave for reclaim code to flush */
        error = ENOENT;
        if (xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
                goto out_unlock;

        /* If we can't grab the inode, it must on it's way to reclaim. */
        if (!igrab(inode))
                goto out_unlock;

        if (is_bad_inode(inode)) {
                IRELE(ip);
                goto out_unlock;
        }

        /* inode is valid */
        error = 0;
out_unlock:
        read_unlock(&pag->pag_ici_lock);
        return error;
}

STATIC int
xfs_sync_inode_data(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        int                     flags)
{
        struct inode            *inode = VFS_I(ip);
        struct address_space *mapping = inode->i_mapping;
        int                     error = 0;

        error = xfs_sync_inode_valid(ip, pag);
        if (error)
                return error;

        if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
                goto out_wait;

        if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) {
                if (flags & SYNC_TRYLOCK)
                        goto out_wait;
                xfs_ilock(ip, XFS_IOLOCK_SHARED);
        }

        error = xfs_flush_pages(ip, 0, -1, (flags & SYNC_WAIT) ?
                                0 : XFS_B_ASYNC, FI_NONE);
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);

 out_wait:
        if (flags & SYNC_WAIT)
                xfs_ioend_wait(ip);
        IRELE(ip);
        return error;
}

STATIC int
xfs_sync_inode_attr(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        int                     flags)
{
        int                     error = 0;

        error = xfs_sync_inode_valid(ip, pag);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_inode_clean(ip))
                goto out_unlock;
        if (!xfs_iflock_nowait(ip)) {
                if (!(flags & SYNC_WAIT))
                        goto out_unlock;
                xfs_iflock(ip);
        }

        if (xfs_inode_clean(ip)) {
                xfs_ifunlock(ip);
                goto out_unlock;
        }

        error = xfs_iflush(ip, (flags & SYNC_WAIT) ?
                           XFS_IFLUSH_SYNC : XFS_IFLUSH_DELWRI);

 out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_SHARED);
        IRELE(ip);
        return error;
}

/*
 * Write out pagecache data for the whole filesystem.
 */
int
xfs_sync_data(
        struct xfs_mount        *mp,
        int                     flags)
{
        int                     error;

        ASSERT((flags & ~(SYNC_TRYLOCK|SYNC_WAIT)) == 0);

        error = xfs_inode_ag_iterator(mp, xfs_sync_inode_data, flags,
                                      XFS_ICI_NO_TAG, 0, NULL);
        if (error)
                return XFS_ERROR(error);

        xfs_log_force(mp, 0,
                      (flags & SYNC_WAIT) ?
                       XFS_LOG_FORCE | XFS_LOG_SYNC :
                       XFS_LOG_FORCE);
        return 0;
}

/*
 * Write out inode metadata (attributes) for the whole filesystem.
 */
int
xfs_sync_attr(
        struct xfs_mount        *mp,
        int                     flags)
{
        ASSERT((flags & ~SYNC_WAIT) == 0);

        return xfs_inode_ag_iterator(mp, xfs_sync_inode_attr, flags,
                                     XFS_ICI_NO_TAG, 0, NULL);
}

STATIC int
xfs_commit_dummy_trans(
        struct xfs_mount        *mp,
        uint                    flags)
{
        struct xfs_inode        *ip = mp->m_rootip;
        struct xfs_trans        *tp;
        int                     error;
        int                     log_flags = XFS_LOG_FORCE;

        if (flags & SYNC_WAIT)
                log_flags |= XFS_LOG_SYNC;

        /*
         * Put a dummy transaction in the log to tell recovery
         * that all others are OK.
         */
        tp = xfs_trans_alloc(mp, XFS_TRANS_DUMMY1);
        error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0);
        if (error) {
                xfs_trans_cancel(tp, 0);
                return error;
        }

        xfs_ilock(ip, XFS_ILOCK_EXCL);

        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
        xfs_trans_ihold(tp, ip);
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
        error = xfs_trans_commit(tp, 0);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        /* the log force ensures this transaction is pushed to disk */
        xfs_log_force(mp, 0, log_flags);
        return error;
}

int
xfs_sync_fsdata(
        struct xfs_mount        *mp,
        int                     flags)
{
        struct xfs_buf          *bp;
        struct xfs_buf_log_item *bip;
        int                     error = 0;

        /*
         * If this is xfssyncd() then only sync the superblock if we can
         * lock it without sleeping and it is not pinned.
         */
        if (flags & SYNC_TRYLOCK) {
                ASSERT(!(flags & SYNC_WAIT));

                bp = xfs_getsb(mp, XFS_BUF_TRYLOCK);
                if (!bp)
                        goto out;

                bip = XFS_BUF_FSPRIVATE(bp, struct xfs_buf_log_item *);
                if (!bip || !xfs_buf_item_dirty(bip) || XFS_BUF_ISPINNED(bp))
                        goto out_brelse;
        } else {
                bp = xfs_getsb(mp, 0);

                /*
                 * If the buffer is pinned then push on the log so we won't
                 * get stuck waiting in the write for someone, maybe
                 * ourselves, to flush the log.
                 *
                 * Even though we just pushed the log above, we did not have
                 * the superblock buffer locked at that point so it can
                 * become pinned in between there and here.
                 */
                if (XFS_BUF_ISPINNED(bp))
                        xfs_log_force(mp, 0, XFS_LOG_FORCE);
        }


        if (flags & SYNC_WAIT)
                XFS_BUF_UNASYNC(bp);
        else
                XFS_BUF_ASYNC(bp);

        error = xfs_bwrite(mp, bp);
        if (error)
                return error;

        /*
         * If this is a data integrity sync make sure all pending buffers
         * are flushed out for the log coverage check below.
         */
        if (flags & SYNC_WAIT)
                xfs_flush_buftarg(mp->m_ddev_targp, 1);

        if (xfs_log_need_covered(mp))
                error = xfs_commit_dummy_trans(mp, flags);
        return error;

 out_brelse:
        xfs_buf_relse(bp);
 out:
        return error;
}

/*
 * When remounting a filesystem read-only or freezing the filesystem, we have
 * two phases to execute. This first phase is syncing the data before we
 * quiesce the filesystem, and the second is flushing all the inodes out after
 * we've waited for all the transactions created by the first phase to
 * complete. The second phase ensures that the inodes are written to their
 * location on disk rather than just existing in transactions in the log. This
 * means after a quiesce there is no log replay required to write the inodes to
 * disk (this is the main difference between a sync and a quiesce).
 */
/*
 * First stage of freeze - no writers will make progress now we are here,
 * so we flush delwri and delalloc buffers here, then wait for all I/O to
 * complete.  Data is frozen at that point. Metadata is not frozen,
 * transactions can still occur here so don't bother flushing the buftarg
 * because it'll just get dirty again.
 */
int
xfs_quiesce_data(
        struct xfs_mount        *mp)
{
        int error;

        /* push non-blocking */
        xfs_sync_data(mp, 0);
        xfs_qm_sync(mp, SYNC_TRYLOCK);

        /* push and block till complete */
        xfs_sync_data(mp, SYNC_WAIT);
        xfs_qm_sync(mp, SYNC_WAIT);

        /* drop inode references pinned by filestreams */
        xfs_filestream_flush(mp);

        /* write superblock and hoover up shutdown errors */
        error = xfs_sync_fsdata(mp, SYNC_WAIT);

        /* flush data-only devices */
        if (mp->m_rtdev_targp)
                XFS_bflush(mp->m_rtdev_targp);

        return error;
}

STATIC void
xfs_quiesce_fs(
        struct xfs_mount        *mp)
{
        int     count = 0, pincount;

        xfs_flush_buftarg(mp->m_ddev_targp, 0);
        xfs_reclaim_inodes(mp, XFS_IFLUSH_DELWRI_ELSE_ASYNC);

        /*
         * This loop must run at least twice.  The first instance of the loop
         * will flush most meta data but that will generate more meta data
         * (typically directory updates).  Which then must be flushed and
         * logged before we can write the unmount record.
         */
        do {
                xfs_sync_attr(mp, SYNC_WAIT);
                pincount = xfs_flush_buftarg(mp->m_ddev_targp, 1);
                if (!pincount) {
                        delay(50);
                        count++;
                }
        } while (count < 2);
}

/*
 * Second stage of a quiesce. The data is already synced, now we have to take
 * care of the metadata. New transactions are already blocked, so we need to
 * wait for any remaining transactions to drain out before proceding.
 */
void
xfs_quiesce_attr(
        struct xfs_mount        *mp)
{
        int     error = 0;

        /* wait for all modifications to complete */
        while (atomic_read(&mp->m_active_trans) > 0)
                delay(100);

        /* flush inodes and push all remaining buffers out to disk */
        xfs_quiesce_fs(mp);

        /*
         * Just warn here till VFS can correctly support
         * read-only remount without racing.
         */
        WARN_ON(atomic_read(&mp->m_active_trans) != 0);

        /* Push the superblock and write an unmount record */
        error = xfs_log_sbcount(mp, 1);
        if (error)
                xfs_fs_cmn_err(CE_WARN, mp,
                                "xfs_attr_quiesce: failed to log sb changes. "
                                "Frozen image may not be consistent.");
        xfs_log_unmount_write(mp);
        xfs_unmountfs_writesb(mp);
}

/*
 * Enqueue a work item to be picked up by the vfs xfssyncd thread.
 * Doing this has two advantages:
 * - It saves on stack space, which is tight in certain situations
 * - It can be used (with care) as a mechanism to avoid deadlocks.
 * Flushing while allocating in a full filesystem requires both.
 */
STATIC void
xfs_syncd_queue_work(
        struct xfs_mount *mp,
        void            *data,
        void            (*syncer)(struct xfs_mount *, void *),
        struct completion *completion)
{
        struct xfs_sync_work *work;

        work = kmem_alloc(sizeof(struct xfs_sync_work), KM_SLEEP);
        INIT_LIST_HEAD(&work->w_list);
        work->w_syncer = syncer;
        work->w_data = data;
        work->w_mount = mp;
        work->w_completion = completion;
        spin_lock(&mp->m_sync_lock);
        list_add_tail(&work->w_list, &mp->m_sync_list);
        spin_unlock(&mp->m_sync_lock);
        wake_up_process(mp->m_sync_task);
}

/*
 * Flush delayed allocate data, attempting to free up reserved space
 * from existing allocations.  At this point a new allocation attempt
 * has failed with ENOSPC and we are in the process of scratching our
 * heads, looking about for more room...
 */
STATIC void
xfs_flush_inodes_work(
        struct xfs_mount *mp,
        void            *arg)
{
        struct inode    *inode = arg;
        xfs_sync_data(mp, SYNC_TRYLOCK);
        xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);
        iput(inode);
}

void
xfs_flush_inodes(
        xfs_inode_t     *ip)
{
        struct inode    *inode = VFS_I(ip);
        DECLARE_COMPLETION_ONSTACK(completion);

        igrab(inode);
        xfs_syncd_queue_work(ip->i_mount, inode, xfs_flush_inodes_work, &completion);
        wait_for_completion(&completion);
        xfs_log_force(ip->i_mount, (xfs_lsn_t)0, XFS_LOG_FORCE|XFS_LOG_SYNC);
}

/*
 * Every sync period we need to unpin all items, reclaim inodes, sync
 * quota and write out the superblock. We might need to cover the log
 * to indicate it is idle.
 */
STATIC void
xfs_sync_worker(
        struct xfs_mount *mp,
        void            *unused)
{
        int             error;

        if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
                xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
                xfs_reclaim_inodes(mp, XFS_IFLUSH_DELWRI_ELSE_ASYNC);
                /* dgc: errors ignored here */
                error = xfs_qm_sync(mp, SYNC_TRYLOCK);
                error = xfs_sync_fsdata(mp, SYNC_TRYLOCK);
        }
        mp->m_sync_seq++;
        wake_up(&mp->m_wait_single_sync_task);
}

STATIC int
xfssyncd(
        void                    *arg)
{
        struct xfs_mount        *mp = arg;
        long                    timeleft;
        xfs_sync_work_t         *work, *n;
        LIST_HEAD               (tmp);

        set_freezable();
        timeleft = xfs_syncd_centisecs * msecs_to_jiffies(10);
        for (;;) {
                timeleft = schedule_timeout_interruptible(timeleft);
                /* swsusp */
                try_to_freeze();
                if (kthread_should_stop() && list_empty(&mp->m_sync_list))
                        break;

                spin_lock(&mp->m_sync_lock);
                /*
                 * We can get woken by laptop mode, to do a sync -
                 * that's the (only!) case where the list would be
                 * empty with time remaining.
                 */
                if (!timeleft || list_empty(&mp->m_sync_list)) {
                        if (!timeleft)
                                timeleft = xfs_syncd_centisecs *
                                                        msecs_to_jiffies(10);
                        INIT_LIST_HEAD(&mp->m_sync_work.w_list);
                        list_add_tail(&mp->m_sync_work.w_list,
                                        &mp->m_sync_list);
                }
                list_for_each_entry_safe(work, n, &mp->m_sync_list, w_list)
                        list_move(&work->w_list, &tmp);
                spin_unlock(&mp->m_sync_lock);

                list_for_each_entry_safe(work, n, &tmp, w_list) {
                        (*work->w_syncer)(mp, work->w_data);
                        list_del(&work->w_list);
                        if (work == &mp->m_sync_work)
                                continue;
                        if (work->w_completion)
                                complete(work->w_completion);
                        kmem_free(work);
                }
        }

        return 0;
}

int
xfs_syncd_init(
        struct xfs_mount        *mp)
{
        mp->m_sync_work.w_syncer = xfs_sync_worker;
        mp->m_sync_work.w_mount = mp;
        mp->m_sync_work.w_completion = NULL;
        mp->m_sync_task = kthread_run(xfssyncd, mp, "xfssyncd");
        if (IS_ERR(mp->m_sync_task))
                return -PTR_ERR(mp->m_sync_task);
        return 0;
}

void
xfs_syncd_stop(
        struct xfs_mount        *mp)
{
        kthread_stop(mp->m_sync_task);
}

void
__xfs_inode_set_reclaim_tag(
        struct xfs_perag        *pag,
        struct xfs_inode        *ip)
{
        radix_tree_tag_set(&pag->pag_ici_root,
                           XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
                           XFS_ICI_RECLAIM_TAG);
        pag->pag_ici_reclaimable++;
}

/*
 * We set the inode flag atomically with the radix tree tag.
 * Once we get tag lookups on the radix tree, this inode flag
 * can go away.
 */
void
xfs_inode_set_reclaim_tag(
        xfs_inode_t     *ip)
{
        xfs_mount_t     *mp = ip->i_mount;
        xfs_perag_t     *pag = xfs_get_perag(mp, ip->i_ino);

        write_lock(&pag->pag_ici_lock);
        spin_lock(&ip->i_flags_lock);
        __xfs_inode_set_reclaim_tag(pag, ip);
        __xfs_iflags_set(ip, XFS_IRECLAIMABLE);
        spin_unlock(&ip->i_flags_lock);
        write_unlock(&pag->pag_ici_lock);
        xfs_put_perag(mp, pag);
}

void
__xfs_inode_clear_reclaim(
        xfs_perag_t     *pag,
        xfs_inode_t     *ip)
{
        pag->pag_ici_reclaimable--;
}

void
__xfs_inode_clear_reclaim_tag(
       xfs_mount_t     *mp,
       xfs_perag_t     *pag,
       xfs_inode_t     *ip)
{
       radix_tree_tag_clear(&pag->pag_ici_root,
                       XFS_INO_TO_AGINO(mp, ip->i_ino), XFS_ICI_RECLAIM_TAG);
       __xfs_inode_clear_reclaim(pag, ip);
}

STATIC int
xfs_reclaim_inode(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        int                     sync_mode)
{
        /*
         * The radix tree lock here protects a thread in xfs_iget from racing
         * with us starting reclaim on the inode.  Once we have the
         * XFS_IRECLAIM flag set it will not touch us.
         */
        spin_lock(&ip->i_flags_lock);
        ASSERT_ALWAYS(__xfs_iflags_test(ip, XFS_IRECLAIMABLE));
        if (__xfs_iflags_test(ip, XFS_IRECLAIM)) {
                /* ignore as it is already under reclaim */
                spin_unlock(&ip->i_flags_lock);
                write_unlock(&pag->pag_ici_lock);
                return 0;
        }
        __xfs_iflags_set(ip, XFS_IRECLAIM);
        spin_unlock(&ip->i_flags_lock);
        write_unlock(&pag->pag_ici_lock);

        /*
         * If the inode is still dirty, then flush it out.  If the inode
         * is not in the AIL, then it will be OK to flush it delwri as
         * long as xfs_iflush() does not keep any references to the inode.
         * We leave that decision up to xfs_iflush() since it has the
         * knowledge of whether it's OK to simply do a delwri flush of
         * the inode or whether we need to wait until the inode is
         * pulled from the AIL.
         * We get the flush lock regardless, though, just to make sure
         * we don't free it while it is being flushed.
         */
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_iflock(ip);

        /*
         * In the case of a forced shutdown we rely on xfs_iflush() to
         * wait for the inode to be unpinned before returning an error.
         */
        if (!is_bad_inode(VFS_I(ip)) && xfs_iflush(ip, sync_mode) == 0) {
                /* synchronize with xfs_iflush_done */
                xfs_iflock(ip);
                xfs_ifunlock(ip);
        }

        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        xfs_ireclaim(ip);
        return 0;
}

int
xfs_reclaim_inodes(
        xfs_mount_t     *mp,
        int             mode)
{
        return xfs_inode_ag_iterator(mp, xfs_reclaim_inode, mode,
                                        XFS_ICI_RECLAIM_TAG, 1, NULL);
}

/*
 * Shrinker infrastructure.
 *
 * This is all far more complex than it needs to be. It adds a global list of
 * mounts because the shrinkers can only call a global context. We need to make
 * the shrinkers pass a context to avoid the need for global state.
 */
static LIST_HEAD(xfs_mount_list);
static struct rw_semaphore xfs_mount_list_lock;

static int
xfs_reclaim_inode_shrink(
        int             nr_to_scan,
        gfp_t           gfp_mask)
{
        struct xfs_mount *mp;
        xfs_agnumber_t  ag;
        int             reclaimable = 0;

        if (nr_to_scan) {
                if (!(gfp_mask & __GFP_FS))
                        return -1;

                down_read(&xfs_mount_list_lock);
                list_for_each_entry(mp, &xfs_mount_list, m_mplist) {
                        xfs_inode_ag_iterator(mp, xfs_reclaim_inode, 0,
                                        XFS_ICI_RECLAIM_TAG, 1, &nr_to_scan);
                        if (nr_to_scan <= 0)
                                break;
                }
                up_read(&xfs_mount_list_lock);
        }

        down_read(&xfs_mount_list_lock);
        list_for_each_entry(mp, &xfs_mount_list, m_mplist) {
                for (ag = 0; ag < mp->m_sb.sb_agcount; ag++) {

                        if (!mp->m_perag[ag].pag_ici_init)
                                continue;
                        reclaimable += mp->m_perag[ag].pag_ici_reclaimable;
                }
        }
        up_read(&xfs_mount_list_lock);
        return reclaimable;
}

static struct shrinker xfs_inode_shrinker = {
        .shrink = xfs_reclaim_inode_shrink,
        .seeks = DEFAULT_SEEKS,
};

void __init
xfs_inode_shrinker_init(void)
{
        init_rwsem(&xfs_mount_list_lock);
        register_shrinker(&xfs_inode_shrinker);
}

void
xfs_inode_shrinker_destroy(void)
{
        ASSERT(list_empty(&xfs_mount_list));
        unregister_shrinker(&xfs_inode_shrinker);
}

void
xfs_inode_shrinker_register(
        struct xfs_mount        *mp)
{
        down_write(&xfs_mount_list_lock);
        list_add_tail(&mp->m_mplist, &xfs_mount_list);
        up_write(&xfs_mount_list_lock);
}

void
xfs_inode_shrinker_unregister(
        struct xfs_mount        *mp)
{
        down_write(&xfs_mount_list_lock);
        list_del(&mp->m_mplist);
        up_write(&xfs_mount_list_lock);
}