Linux 3.12.5

[linux/fpc-iii.git] / fs / xfs / xfs_icache.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_format.h"
#include "xfs_types.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "xfs_dinode.h"
#include "xfs_error.h"
#include "xfs_filestream.h"
#include "xfs_inode_item.h"
#include "xfs_quota.h"
#include "xfs_trace.h"
#include "xfs_fsops.h"
#include "xfs_icache.h"
#include "xfs_bmap_util.h"

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

STATIC void __xfs_inode_clear_reclaim_tag(struct xfs_mount *mp,
                                struct xfs_perag *pag, struct xfs_inode *ip);

/*
 * Allocate and initialise an xfs_inode.
 */
struct xfs_inode *
xfs_inode_alloc(
        struct xfs_mount        *mp,
        xfs_ino_t               ino)
{
        struct xfs_inode        *ip;

        /*
         * if this didn't occur in transactions, we could use
         * KM_MAYFAIL and return NULL here on ENOMEM. Set the
         * code up to do this anyway.
         */
        ip = kmem_zone_alloc(xfs_inode_zone, KM_SLEEP);
        if (!ip)
                return NULL;
        if (inode_init_always(mp->m_super, VFS_I(ip))) {
                kmem_zone_free(xfs_inode_zone, ip);
                return NULL;
        }

        ASSERT(atomic_read(&ip->i_pincount) == 0);
        ASSERT(!spin_is_locked(&ip->i_flags_lock));
        ASSERT(!xfs_isiflocked(ip));
        ASSERT(ip->i_ino == 0);

        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);

        /* initialise the xfs inode */
        ip->i_ino = ino;
        ip->i_mount = mp;
        memset(&ip->i_imap, 0, sizeof(struct xfs_imap));
        ip->i_afp = NULL;
        memset(&ip->i_df, 0, sizeof(xfs_ifork_t));
        ip->i_flags = 0;
        ip->i_delayed_blks = 0;
        memset(&ip->i_d, 0, sizeof(xfs_icdinode_t));

        return ip;
}

STATIC void
xfs_inode_free_callback(
        struct rcu_head         *head)
{
        struct inode            *inode = container_of(head, struct inode, i_rcu);
        struct xfs_inode        *ip = XFS_I(inode);

        kmem_zone_free(xfs_inode_zone, ip);
}

void
xfs_inode_free(
        struct xfs_inode        *ip)
{
        switch (ip->i_d.di_mode & S_IFMT) {
        case S_IFREG:
        case S_IFDIR:
        case S_IFLNK:
                xfs_idestroy_fork(ip, XFS_DATA_FORK);
                break;
        }

        if (ip->i_afp)
                xfs_idestroy_fork(ip, XFS_ATTR_FORK);

        if (ip->i_itemp) {
                ASSERT(!(ip->i_itemp->ili_item.li_flags & XFS_LI_IN_AIL));
                xfs_inode_item_destroy(ip);
                ip->i_itemp = NULL;
        }

        /*
         * Because we use RCU freeing we need to ensure the inode always
         * appears to be reclaimed with an invalid inode number when in the
         * free state. The ip->i_flags_lock provides the barrier against lookup
         * races.
         */
        spin_lock(&ip->i_flags_lock);
        ip->i_flags = XFS_IRECLAIM;
        ip->i_ino = 0;
        spin_unlock(&ip->i_flags_lock);

        /* asserts to verify all state is correct here */
        ASSERT(atomic_read(&ip->i_pincount) == 0);
        ASSERT(!xfs_isiflocked(ip));

        call_rcu(&VFS_I(ip)->i_rcu, xfs_inode_free_callback);
}

/*
 * Check the validity of the inode we just found it the cache
 */
static int
xfs_iget_cache_hit(
        struct xfs_perag        *pag,
        struct xfs_inode        *ip,
        xfs_ino_t               ino,
        int                     flags,
        int                     lock_flags) __releases(RCU)
{
        struct inode            *inode = VFS_I(ip);
        struct xfs_mount        *mp = ip->i_mount;
        int                     error;

        /*
         * check for re-use of an inode within an RCU grace period due to the
         * radix tree nodes not being updated yet. We monitor for this by
         * setting the inode number to zero before freeing the inode structure.
         * If the inode has been reallocated and set up, then the inode number
         * will not match, so check for that, too.
         */
        spin_lock(&ip->i_flags_lock);
        if (ip->i_ino != ino) {
                trace_xfs_iget_skip(ip);
                XFS_STATS_INC(xs_ig_frecycle);
                error = EAGAIN;
                goto out_error;
        }


        /*
         * If we are racing with another cache hit that is currently
         * instantiating this inode or currently recycling it out of
         * reclaimabe state, wait for the initialisation to complete
         * before continuing.
         *
         * XXX(hch): eventually we should do something equivalent to
         *           wait_on_inode to wait for these flags to be cleared
         *           instead of polling for it.
         */
        if (ip->i_flags & (XFS_INEW|XFS_IRECLAIM)) {
                trace_xfs_iget_skip(ip);
                XFS_STATS_INC(xs_ig_frecycle);
                error = EAGAIN;
                goto out_error;
        }

        /*
         * If lookup is racing with unlink return an error immediately.
         */
        if (ip->i_d.di_mode == 0 && !(flags & XFS_IGET_CREATE)) {
                error = ENOENT;
                goto out_error;
        }

        /*
         * If IRECLAIMABLE is set, we've torn down the VFS inode already.
         * Need to carefully get it back into useable state.
         */
        if (ip->i_flags & XFS_IRECLAIMABLE) {
                trace_xfs_iget_reclaim(ip);

                /*
                 * We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
                 * from stomping over us while we recycle the inode.  We can't
                 * clear the radix tree reclaimable tag yet as it requires
                 * pag_ici_lock to be held exclusive.
                 */
                ip->i_flags |= XFS_IRECLAIM;

                spin_unlock(&ip->i_flags_lock);
                rcu_read_unlock();

                error = -inode_init_always(mp->m_super, inode);
                if (error) {
                        /*
                         * Re-initializing the inode failed, and we are in deep
                         * trouble.  Try to re-add it to the reclaim list.
                         */
                        rcu_read_lock();
                        spin_lock(&ip->i_flags_lock);

                        ip->i_flags &= ~(XFS_INEW | XFS_IRECLAIM);
                        ASSERT(ip->i_flags & XFS_IRECLAIMABLE);
                        trace_xfs_iget_reclaim_fail(ip);
                        goto out_error;
                }

                spin_lock(&pag->pag_ici_lock);
                spin_lock(&ip->i_flags_lock);

                /*
                 * Clear the per-lifetime state in the inode as we are now
                 * effectively a new inode and need to return to the initial
                 * state before reuse occurs.
                 */
                ip->i_flags &= ~XFS_IRECLAIM_RESET_FLAGS;
                ip->i_flags |= XFS_INEW;
                __xfs_inode_clear_reclaim_tag(mp, pag, ip);
                inode->i_state = I_NEW;

                ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
                mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);

                spin_unlock(&ip->i_flags_lock);
                spin_unlock(&pag->pag_ici_lock);
        } else {
                /* If the VFS inode is being torn down, pause and try again. */
                if (!igrab(inode)) {
                        trace_xfs_iget_skip(ip);
                        error = EAGAIN;
                        goto out_error;
                }

                /* We've got a live one. */
                spin_unlock(&ip->i_flags_lock);
                rcu_read_unlock();
                trace_xfs_iget_hit(ip);
        }

        if (lock_flags != 0)
                xfs_ilock(ip, lock_flags);

        xfs_iflags_clear(ip, XFS_ISTALE | XFS_IDONTCACHE);
        XFS_STATS_INC(xs_ig_found);

        return 0;

out_error:
        spin_unlock(&ip->i_flags_lock);
        rcu_read_unlock();
        return error;
}


static int
xfs_iget_cache_miss(
        struct xfs_mount        *mp,
        struct xfs_perag        *pag,
        xfs_trans_t             *tp,
        xfs_ino_t               ino,
        struct xfs_inode        **ipp,
        int                     flags,
        int                     lock_flags)
{
        struct xfs_inode        *ip;
        int                     error;
        xfs_agino_t             agino = XFS_INO_TO_AGINO(mp, ino);
        int                     iflags;

        ip = xfs_inode_alloc(mp, ino);
        if (!ip)
                return ENOMEM;

        error = xfs_iread(mp, tp, ip, flags);
        if (error)
                goto out_destroy;

        trace_xfs_iget_miss(ip);

        if ((ip->i_d.di_mode == 0) && !(flags & XFS_IGET_CREATE)) {
                error = ENOENT;
                goto out_destroy;
        }

        /*
         * Preload the radix tree so we can insert safely under the
         * write spinlock. Note that we cannot sleep inside the preload
         * region. Since we can be called from transaction context, don't
         * recurse into the file system.
         */
        if (radix_tree_preload(GFP_NOFS)) {
                error = EAGAIN;
                goto out_destroy;
        }

        /*
         * Because the inode hasn't been added to the radix-tree yet it can't
         * be found by another thread, so we can do the non-sleeping lock here.
         */
        if (lock_flags) {
                if (!xfs_ilock_nowait(ip, lock_flags))
                        BUG();
        }

        /*
         * These values must be set before inserting the inode into the radix
         * tree as the moment it is inserted a concurrent lookup (allowed by the
         * RCU locking mechanism) can find it and that lookup must see that this
         * is an inode currently under construction (i.e. that XFS_INEW is set).
         * The ip->i_flags_lock that protects the XFS_INEW flag forms the
         * memory barrier that ensures this detection works correctly at lookup
         * time.
         */
        iflags = XFS_INEW;
        if (flags & XFS_IGET_DONTCACHE)
                iflags |= XFS_IDONTCACHE;
        ip->i_udquot = NULL;
        ip->i_gdquot = NULL;
        ip->i_pdquot = NULL;
        xfs_iflags_set(ip, iflags);

        /* insert the new inode */
        spin_lock(&pag->pag_ici_lock);
        error = radix_tree_insert(&pag->pag_ici_root, agino, ip);
        if (unlikely(error)) {
                WARN_ON(error != -EEXIST);
                XFS_STATS_INC(xs_ig_dup);
                error = EAGAIN;
                goto out_preload_end;
        }
        spin_unlock(&pag->pag_ici_lock);
        radix_tree_preload_end();

        *ipp = ip;
        return 0;

out_preload_end:
        spin_unlock(&pag->pag_ici_lock);
        radix_tree_preload_end();
        if (lock_flags)
                xfs_iunlock(ip, lock_flags);
out_destroy:
        __destroy_inode(VFS_I(ip));
        xfs_inode_free(ip);
        return error;
}

/*
 * Look up an inode by number in the given file system.
 * The inode is looked up in the cache held in each AG.
 * If the inode is found in the cache, initialise the vfs inode
 * if necessary.
 *
 * If it is not in core, read it in from the file system's device,
 * add it to the cache and initialise the vfs inode.
 *
 * The inode is locked according to the value of the lock_flags parameter.
 * This flag parameter indicates how and if the inode's IO lock and inode lock
 * should be taken.
 *
 * mp -- the mount point structure for the current file system.  It points
 *       to the inode hash table.
 * tp -- a pointer to the current transaction if there is one.  This is
 *       simply passed through to the xfs_iread() call.
 * ino -- the number of the inode desired.  This is the unique identifier
 *        within the file system for the inode being requested.
 * lock_flags -- flags indicating how to lock the inode.  See the comment
 *               for xfs_ilock() for a list of valid values.
 */
int
xfs_iget(
        xfs_mount_t     *mp,
        xfs_trans_t     *tp,
        xfs_ino_t       ino,
        uint            flags,
        uint            lock_flags,
        xfs_inode_t     **ipp)
{
        xfs_inode_t     *ip;
        int             error;
        xfs_perag_t     *pag;
        xfs_agino_t     agino;

        /*
         * xfs_reclaim_inode() uses the ILOCK to ensure an inode
         * doesn't get freed while it's being referenced during a
         * radix tree traversal here.  It assumes this function
         * aqcuires only the ILOCK (and therefore it has no need to
         * involve the IOLOCK in this synchronization).
         */
        ASSERT((lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) == 0);

        /* reject inode numbers outside existing AGs */
        if (!ino || XFS_INO_TO_AGNO(mp, ino) >= mp->m_sb.sb_agcount)
                return EINVAL;

        /* get the perag structure and ensure that it's inode capable */
        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ino));
        agino = XFS_INO_TO_AGINO(mp, ino);

again:
        error = 0;
        rcu_read_lock();
        ip = radix_tree_lookup(&pag->pag_ici_root, agino);

        if (ip) {
                error = xfs_iget_cache_hit(pag, ip, ino, flags, lock_flags);
                if (error)
                        goto out_error_or_again;
        } else {
                rcu_read_unlock();
                XFS_STATS_INC(xs_ig_missed);

                error = xfs_iget_cache_miss(mp, pag, tp, ino, &ip,
                                                        flags, lock_flags);
                if (error)
                        goto out_error_or_again;
        }
        xfs_perag_put(pag);

        *ipp = ip;

        /*
         * If we have a real type for an on-disk inode, we can set ops(&unlock)
         * now.  If it's a new inode being created, xfs_ialloc will handle it.
         */
        if (xfs_iflags_test(ip, XFS_INEW) && ip->i_d.di_mode != 0)
                xfs_setup_inode(ip);
        return 0;

out_error_or_again:
        if (error == EAGAIN) {
                delay(1);
                goto again;
        }
        xfs_perag_put(pag);
        return error;
}

/*
 * The inode lookup is done in batches to keep the amount of lock traffic and
 * radix tree lookups to a minimum. The batch size is a trade off between
 * lookup reduction and stack usage. This is in the reclaim path, so we can't
 * be too greedy.
 */
#define XFS_LOOKUP_BATCH        32

STATIC int
xfs_inode_ag_walk_grab(
        struct xfs_inode        *ip)
{
        struct inode            *inode = VFS_I(ip);

        ASSERT(rcu_read_lock_held());

        /*
         * check for stale RCU freed inode
         *
         * If the inode has been reallocated, it doesn't matter if it's not in
         * the AG we are walking - we are walking for writeback, so if it
         * passes all the "valid inode" checks and is dirty, then we'll write
         * it back anyway.  If it has been reallocated and still being
         * initialised, the XFS_INEW check below will catch it.
         */
        spin_lock(&ip->i_flags_lock);
        if (!ip->i_ino)
                goto out_unlock_noent;

        /* avoid new or reclaimable inodes. Leave for reclaim code to flush */
        if (__xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
                goto out_unlock_noent;
        spin_unlock(&ip->i_flags_lock);

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

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

        if (is_bad_inode(inode)) {
                IRELE(ip);
                return ENOENT;
        }

        /* inode is valid */
        return 0;

out_unlock_noent:
        spin_unlock(&ip->i_flags_lock);
        return ENOENT;
}

STATIC int
xfs_inode_ag_walk(
        struct xfs_mount        *mp,
        struct xfs_perag        *pag,
        int                     (*execute)(struct xfs_inode *ip,
                                           struct xfs_perag *pag, int flags,
                                           void *args),
        int                     flags,
        void                    *args,
        int                     tag)
{
        uint32_t                first_index;
        int                     last_error = 0;
        int                     skipped;
        int                     done;
        int                     nr_found;

restart:
        done = 0;
        skipped = 0;
        first_index = 0;
        nr_found = 0;
        do {
                struct xfs_inode *batch[XFS_LOOKUP_BATCH];
                int             error = 0;
                int             i;

                rcu_read_lock();

                if (tag == -1)
                        nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,
                                        (void **)batch, first_index,
                                        XFS_LOOKUP_BATCH);
                else
                        nr_found = radix_tree_gang_lookup_tag(
                                        &pag->pag_ici_root,
                                        (void **) batch, first_index,
                                        XFS_LOOKUP_BATCH, tag);

                if (!nr_found) {
                        rcu_read_unlock();
                        break;
                }

                /*
                 * Grab the inodes before we drop the lock. if we found
                 * nothing, nr == 0 and the loop will be skipped.
                 */
                for (i = 0; i < nr_found; i++) {
                        struct xfs_inode *ip = batch[i];

                        if (done || xfs_inode_ag_walk_grab(ip))
                                batch[i] = 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.
                         *
                         * Because we may see inodes that are from the wrong AG
                         * due to RCU freeing and reallocation, only update the
                         * index if it lies in this AG. It was a race that lead
                         * us to see this inode, so another lookup from the
                         * same index will not find it again.
                         */
                        if (XFS_INO_TO_AGNO(mp, ip->i_ino) != pag->pag_agno)
                                continue;
                        first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
                        if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
                                done = 1;
                }

                /* unlock now we've grabbed the inodes. */
                rcu_read_unlock();

                for (i = 0; i < nr_found; i++) {
                        if (!batch[i])
                                continue;
                        error = execute(batch[i], pag, flags, args);
                        IRELE(batch[i]);
                        if (error == EAGAIN) {
                                skipped++;
                                continue;
                        }
                        if (error && last_error != EFSCORRUPTED)
                                last_error = error;
                }

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

                cond_resched();

        } while (nr_found && !done);

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

/*
 * Background scanning to trim post-EOF preallocated space. This is queued
 * based on the 'speculative_prealloc_lifetime' tunable (5m by default).
 */
STATIC void
xfs_queue_eofblocks(
        struct xfs_mount *mp)
{
        rcu_read_lock();
        if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_EOFBLOCKS_TAG))
                queue_delayed_work(mp->m_eofblocks_workqueue,
                                   &mp->m_eofblocks_work,
                                   msecs_to_jiffies(xfs_eofb_secs * 1000));
        rcu_read_unlock();
}

void
xfs_eofblocks_worker(
        struct work_struct *work)
{
        struct xfs_mount *mp = container_of(to_delayed_work(work),
                                struct xfs_mount, m_eofblocks_work);
        xfs_icache_free_eofblocks(mp, NULL);
        xfs_queue_eofblocks(mp);
}

int
xfs_inode_ag_iterator(
        struct xfs_mount        *mp,
        int                     (*execute)(struct xfs_inode *ip,
                                           struct xfs_perag *pag, int flags,
                                           void *args),
        int                     flags,
        void                    *args)
{
        struct xfs_perag        *pag;
        int                     error = 0;
        int                     last_error = 0;
        xfs_agnumber_t          ag;

        ag = 0;
        while ((pag = xfs_perag_get(mp, ag))) {
                ag = pag->pag_agno + 1;
                error = xfs_inode_ag_walk(mp, pag, execute, flags, args, -1);
                xfs_perag_put(pag);
                if (error) {
                        last_error = error;
                        if (error == EFSCORRUPTED)
                                break;
                }
        }
        return XFS_ERROR(last_error);
}

int
xfs_inode_ag_iterator_tag(
        struct xfs_mount        *mp,
        int                     (*execute)(struct xfs_inode *ip,
                                           struct xfs_perag *pag, int flags,
                                           void *args),
        int                     flags,
        void                    *args,
        int                     tag)
{
        struct xfs_perag        *pag;
        int                     error = 0;
        int                     last_error = 0;
        xfs_agnumber_t          ag;

        ag = 0;
        while ((pag = xfs_perag_get_tag(mp, ag, tag))) {
                ag = pag->pag_agno + 1;
                error = xfs_inode_ag_walk(mp, pag, execute, flags, args, tag);
                xfs_perag_put(pag);
                if (error) {
                        last_error = error;
                        if (error == EFSCORRUPTED)
                                break;
                }
        }
        return XFS_ERROR(last_error);
}

/*
 * Queue a new inode reclaim pass if there are reclaimable inodes and there
 * isn't a reclaim pass already in progress. By default it runs every 5s based
 * on the xfs periodic sync default of 30s. Perhaps this should have it's own
 * tunable, but that can be done if this method proves to be ineffective or too
 * aggressive.
 */
static void
xfs_reclaim_work_queue(
        struct xfs_mount        *mp)
{

        rcu_read_lock();
        if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
                queue_delayed_work(mp->m_reclaim_workqueue, &mp->m_reclaim_work,
                        msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
        }
        rcu_read_unlock();
}

/*
 * This is a fast pass over the inode cache to try to get reclaim moving on as
 * many inodes as possible in a short period of time. It kicks itself every few
 * seconds, as well as being kicked by the inode cache shrinker when memory
 * goes low. It scans as quickly as possible avoiding locked inodes or those
 * already being flushed, and once done schedules a future pass.
 */
void
xfs_reclaim_worker(
        struct work_struct *work)
{
        struct xfs_mount *mp = container_of(to_delayed_work(work),
                                        struct xfs_mount, m_reclaim_work);

        xfs_reclaim_inodes(mp, SYNC_TRYLOCK);
        xfs_reclaim_work_queue(mp);
}

static 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);

        if (!pag->pag_ici_reclaimable) {
                /* propagate the reclaim tag up into the perag radix tree */
                spin_lock(&ip->i_mount->m_perag_lock);
                radix_tree_tag_set(&ip->i_mount->m_perag_tree,
                                XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
                                XFS_ICI_RECLAIM_TAG);
                spin_unlock(&ip->i_mount->m_perag_lock);

                /* schedule periodic background inode reclaim */
                xfs_reclaim_work_queue(ip->i_mount);

                trace_xfs_perag_set_reclaim(ip->i_mount, pag->pag_agno,
                                                        -1, _RET_IP_);
        }
        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)
{
        struct xfs_mount *mp = ip->i_mount;
        struct xfs_perag *pag;

        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
        spin_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);
        spin_unlock(&pag->pag_ici_lock);
        xfs_perag_put(pag);
}

STATIC void
__xfs_inode_clear_reclaim(
        xfs_perag_t     *pag,
        xfs_inode_t     *ip)
{
        pag->pag_ici_reclaimable--;
        if (!pag->pag_ici_reclaimable) {
                /* clear the reclaim tag from the perag radix tree */
                spin_lock(&ip->i_mount->m_perag_lock);
                radix_tree_tag_clear(&ip->i_mount->m_perag_tree,
                                XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
                                XFS_ICI_RECLAIM_TAG);
                spin_unlock(&ip->i_mount->m_perag_lock);
                trace_xfs_perag_clear_reclaim(ip->i_mount, pag->pag_agno,
                                                        -1, _RET_IP_);
        }
}

STATIC 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);
}

/*
 * Grab the inode for reclaim exclusively.
 * Return 0 if we grabbed it, non-zero otherwise.
 */
STATIC int
xfs_reclaim_inode_grab(
        struct xfs_inode        *ip,
        int                     flags)
{
        ASSERT(rcu_read_lock_held());

        /* quick check for stale RCU freed inode */
        if (!ip->i_ino)
                return 1;

        /*
         * If we are asked for non-blocking operation, do unlocked checks to
         * see if the inode already is being flushed or in reclaim to avoid
         * lock traffic.
         */
        if ((flags & SYNC_TRYLOCK) &&
            __xfs_iflags_test(ip, XFS_IFLOCK | XFS_IRECLAIM))
                return 1;

        /*
         * 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.
         *
         * Due to RCU lookup, we may find inodes that have been freed and only
         * have XFS_IRECLAIM set.  Indeed, we may see reallocated inodes that
         * aren't candidates for reclaim at all, so we must check the
         * XFS_IRECLAIMABLE is set first before proceeding to reclaim.
         */
        spin_lock(&ip->i_flags_lock);
        if (!__xfs_iflags_test(ip, XFS_IRECLAIMABLE) ||
            __xfs_iflags_test(ip, XFS_IRECLAIM)) {
                /* not a reclaim candidate. */
                spin_unlock(&ip->i_flags_lock);
                return 1;
        }
        __xfs_iflags_set(ip, XFS_IRECLAIM);
        spin_unlock(&ip->i_flags_lock);
        return 0;
}

/*
 * Inodes in different states need to be treated differently. The following
 * table lists the inode states and the reclaim actions necessary:
 *
 *      inode state          iflush ret         required action
 *      ---------------      ----------         ---------------
 *      bad                     -               reclaim
 *      shutdown                EIO             unpin and reclaim
 *      clean, unpinned         0               reclaim
 *      stale, unpinned         0               reclaim
 *      clean, pinned(*)        0               requeue
 *      stale, pinned           EAGAIN          requeue
 *      dirty, async            -               requeue
 *      dirty, sync             0               reclaim
 *
 * (*) dgc: I don't think the clean, pinned state is possible but it gets
 * handled anyway given the order of checks implemented.
 *
 * Also, because we get the flush lock first, we know that any inode that has
 * been flushed delwri has had the flush completed by the time we check that
 * the inode is clean.
 *
 * Note that because the inode is flushed delayed write by AIL pushing, the
 * flush lock may already be held here and waiting on it can result in very
 * long latencies.  Hence for sync reclaims, where we wait on the flush lock,
 * the caller should push the AIL first before trying to reclaim inodes to
 * minimise the amount of time spent waiting.  For background relaim, we only
 * bother to reclaim clean inodes anyway.
 *
 * Hence the order of actions after gaining the locks should be:
 *      bad             => reclaim
 *      shutdown        => unpin and reclaim
 *      pinned, async   => requeue
 *      pinned, sync    => unpin
 *      stale           => reclaim
 *      clean           => reclaim
 *      dirty, async    => requeue
 *      dirty, sync     => flush, wait and reclaim
 */
STATIC int
xfs_reclaim_inode(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        int                     sync_mode)
{
        struct xfs_buf          *bp = NULL;
        int                     error;

restart:
        error = 0;
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        if (!xfs_iflock_nowait(ip)) {
                if (!(sync_mode & SYNC_WAIT))
                        goto out;
                xfs_iflock(ip);
        }

        if (is_bad_inode(VFS_I(ip)))
                goto reclaim;
        if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
                xfs_iunpin_wait(ip);
                xfs_iflush_abort(ip, false);
                goto reclaim;
        }
        if (xfs_ipincount(ip)) {
                if (!(sync_mode & SYNC_WAIT))
                        goto out_ifunlock;
                xfs_iunpin_wait(ip);
        }
        if (xfs_iflags_test(ip, XFS_ISTALE))
                goto reclaim;
        if (xfs_inode_clean(ip))
                goto reclaim;

        /*
         * Never flush out dirty data during non-blocking reclaim, as it would
         * just contend with AIL pushing trying to do the same job.
         */
        if (!(sync_mode & SYNC_WAIT))
                goto out_ifunlock;

        /*
         * Now we have an inode that needs flushing.
         *
         * Note that xfs_iflush will never block on the inode buffer lock, as
         * xfs_ifree_cluster() can lock the inode buffer before it locks the
         * ip->i_lock, and we are doing the exact opposite here.  As a result,
         * doing a blocking xfs_imap_to_bp() to get the cluster buffer would
         * result in an ABBA deadlock with xfs_ifree_cluster().
         *
         * As xfs_ifree_cluser() must gather all inodes that are active in the
         * cache to mark them stale, if we hit this case we don't actually want
         * to do IO here - we want the inode marked stale so we can simply
         * reclaim it.  Hence if we get an EAGAIN error here,  just unlock the
         * inode, back off and try again.  Hopefully the next pass through will
         * see the stale flag set on the inode.
         */
        error = xfs_iflush(ip, &bp);
        if (error == EAGAIN) {
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                /* backoff longer than in xfs_ifree_cluster */
                delay(2);
                goto restart;
        }

        if (!error) {
                error = xfs_bwrite(bp);
                xfs_buf_relse(bp);
        }

        xfs_iflock(ip);
reclaim:
        xfs_ifunlock(ip);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        XFS_STATS_INC(xs_ig_reclaims);
        /*
         * Remove the inode from the per-AG radix tree.
         *
         * Because radix_tree_delete won't complain even if the item was never
         * added to the tree assert that it's been there before to catch
         * problems with the inode life time early on.
         */
        spin_lock(&pag->pag_ici_lock);
        if (!radix_tree_delete(&pag->pag_ici_root,
                                XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino)))
                ASSERT(0);
        __xfs_inode_clear_reclaim(pag, ip);
        spin_unlock(&pag->pag_ici_lock);

        /*
         * Here we do an (almost) spurious inode lock in order to coordinate
         * with inode cache radix tree lookups.  This is because the lookup
         * can reference the inodes in the cache without taking references.
         *
         * We make that OK here by ensuring that we wait until the inode is
         * unlocked after the lookup before we go ahead and free it.
         */
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_qm_dqdetach(ip);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        xfs_inode_free(ip);
        return error;

out_ifunlock:
        xfs_ifunlock(ip);
out:
        xfs_iflags_clear(ip, XFS_IRECLAIM);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        /*
         * We could return EAGAIN here to make reclaim rescan the inode tree in
         * a short while. However, this just burns CPU time scanning the tree
         * waiting for IO to complete and the reclaim work never goes back to
         * the idle state. Instead, return 0 to let the next scheduled
         * background reclaim attempt to reclaim the inode again.
         */
        return 0;
}

/*
 * Walk the AGs and reclaim the inodes in them. Even if the filesystem is
 * corrupted, we still want to try to reclaim all the inodes. If we don't,
 * then a shut down during filesystem unmount reclaim walk leak all the
 * unreclaimed inodes.
 */
STATIC int
xfs_reclaim_inodes_ag(
        struct xfs_mount        *mp,
        int                     flags,
        int                     *nr_to_scan)
{
        struct xfs_perag        *pag;
        int                     error = 0;
        int                     last_error = 0;
        xfs_agnumber_t          ag;
        int                     trylock = flags & SYNC_TRYLOCK;
        int                     skipped;

restart:
        ag = 0;
        skipped = 0;
        while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
                unsigned long   first_index = 0;
                int             done = 0;
                int             nr_found = 0;

                ag = pag->pag_agno + 1;

                if (trylock) {
                        if (!mutex_trylock(&pag->pag_ici_reclaim_lock)) {
                                skipped++;
                                xfs_perag_put(pag);
                                continue;
                        }
                        first_index = pag->pag_ici_reclaim_cursor;
                } else
                        mutex_lock(&pag->pag_ici_reclaim_lock);

                do {
                        struct xfs_inode *batch[XFS_LOOKUP_BATCH];
                        int     i;

                        rcu_read_lock();
                        nr_found = radix_tree_gang_lookup_tag(
                                        &pag->pag_ici_root,
                                        (void **)batch, first_index,
                                        XFS_LOOKUP_BATCH,
                                        XFS_ICI_RECLAIM_TAG);
                        if (!nr_found) {
                                done = 1;
                                rcu_read_unlock();
                                break;
                        }

                        /*
                         * Grab the inodes before we drop the lock. if we found
                         * nothing, nr == 0 and the loop will be skipped.
                         */
                        for (i = 0; i < nr_found; i++) {
                                struct xfs_inode *ip = batch[i];

                                if (done || xfs_reclaim_inode_grab(ip, flags))
                                        batch[i] = 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.
                                 *
                                 * Because we may see inodes that are from the
                                 * wrong AG due to RCU freeing and
                                 * reallocation, only update the index if it
                                 * lies in this AG. It was a race that lead us
                                 * to see this inode, so another lookup from
                                 * the same index will not find it again.
                                 */
                                if (XFS_INO_TO_AGNO(mp, ip->i_ino) !=
                                                                pag->pag_agno)
                                        continue;
                                first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
                                if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
                                        done = 1;
                        }

                        /* unlock now we've grabbed the inodes. */
                        rcu_read_unlock();

                        for (i = 0; i < nr_found; i++) {
                                if (!batch[i])
                                        continue;
                                error = xfs_reclaim_inode(batch[i], pag, flags);
                                if (error && last_error != EFSCORRUPTED)
                                        last_error = error;
                        }

                        *nr_to_scan -= XFS_LOOKUP_BATCH;

                        cond_resched();

                } while (nr_found && !done && *nr_to_scan > 0);

                if (trylock && !done)
                        pag->pag_ici_reclaim_cursor = first_index;
                else
                        pag->pag_ici_reclaim_cursor = 0;
                mutex_unlock(&pag->pag_ici_reclaim_lock);
                xfs_perag_put(pag);
        }

        /*
         * if we skipped any AG, and we still have scan count remaining, do
         * another pass this time using blocking reclaim semantics (i.e
         * waiting on the reclaim locks and ignoring the reclaim cursors). This
         * ensure that when we get more reclaimers than AGs we block rather
         * than spin trying to execute reclaim.
         */
        if (skipped && (flags & SYNC_WAIT) && *nr_to_scan > 0) {
                trylock = 0;
                goto restart;
        }
        return XFS_ERROR(last_error);
}

int
xfs_reclaim_inodes(
        xfs_mount_t     *mp,
        int             mode)
{
        int             nr_to_scan = INT_MAX;

        return xfs_reclaim_inodes_ag(mp, mode, &nr_to_scan);
}

/*
 * Scan a certain number of inodes for reclaim.
 *
 * When called we make sure that there is a background (fast) inode reclaim in
 * progress, while we will throttle the speed of reclaim via doing synchronous
 * reclaim of inodes. That means if we come across dirty inodes, we wait for
 * them to be cleaned, which we hope will not be very long due to the
 * background walker having already kicked the IO off on those dirty inodes.
 */
long
xfs_reclaim_inodes_nr(
        struct xfs_mount        *mp,
        int                     nr_to_scan)
{
        /* kick background reclaimer and push the AIL */
        xfs_reclaim_work_queue(mp);
        xfs_ail_push_all(mp->m_ail);

        return xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
}

/*
 * Return the number of reclaimable inodes in the filesystem for
 * the shrinker to determine how much to reclaim.
 */
int
xfs_reclaim_inodes_count(
        struct xfs_mount        *mp)
{
        struct xfs_perag        *pag;
        xfs_agnumber_t          ag = 0;
        int                     reclaimable = 0;

        while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
                ag = pag->pag_agno + 1;
                reclaimable += pag->pag_ici_reclaimable;
                xfs_perag_put(pag);
        }
        return reclaimable;
}

STATIC int
xfs_inode_match_id(
        struct xfs_inode        *ip,
        struct xfs_eofblocks    *eofb)
{
        if ((eofb->eof_flags & XFS_EOF_FLAGS_UID) &&
            !uid_eq(VFS_I(ip)->i_uid, eofb->eof_uid))
                return 0;

        if ((eofb->eof_flags & XFS_EOF_FLAGS_GID) &&
            !gid_eq(VFS_I(ip)->i_gid, eofb->eof_gid))
                return 0;

        if ((eofb->eof_flags & XFS_EOF_FLAGS_PRID) &&
            xfs_get_projid(ip) != eofb->eof_prid)
                return 0;

        return 1;
}

STATIC int
xfs_inode_free_eofblocks(
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        int                     flags,
        void                    *args)
{
        int ret;
        struct xfs_eofblocks *eofb = args;

        if (!xfs_can_free_eofblocks(ip, false)) {
                /* inode could be preallocated or append-only */
                trace_xfs_inode_free_eofblocks_invalid(ip);
                xfs_inode_clear_eofblocks_tag(ip);
                return 0;
        }

        /*
         * If the mapping is dirty the operation can block and wait for some
         * time. Unless we are waiting, skip it.
         */
        if (!(flags & SYNC_WAIT) &&
            mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_DIRTY))
                return 0;

        if (eofb) {
                if (!xfs_inode_match_id(ip, eofb))
                        return 0;

                /* skip the inode if the file size is too small */
                if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
                    XFS_ISIZE(ip) < eofb->eof_min_file_size)
                        return 0;
        }

        ret = xfs_free_eofblocks(ip->i_mount, ip, true);

        /* don't revisit the inode if we're not waiting */
        if (ret == EAGAIN && !(flags & SYNC_WAIT))
                ret = 0;

        return ret;
}

int
xfs_icache_free_eofblocks(
        struct xfs_mount        *mp,
        struct xfs_eofblocks    *eofb)
{
        int flags = SYNC_TRYLOCK;

        if (eofb && (eofb->eof_flags & XFS_EOF_FLAGS_SYNC))
                flags = SYNC_WAIT;

        return xfs_inode_ag_iterator_tag(mp, xfs_inode_free_eofblocks, flags,
                                         eofb, XFS_ICI_EOFBLOCKS_TAG);
}

void
xfs_inode_set_eofblocks_tag(
        xfs_inode_t     *ip)
{
        struct xfs_mount *mp = ip->i_mount;
        struct xfs_perag *pag;
        int tagged;

        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
        spin_lock(&pag->pag_ici_lock);
        trace_xfs_inode_set_eofblocks_tag(ip);

        tagged = radix_tree_tagged(&pag->pag_ici_root,
                                   XFS_ICI_EOFBLOCKS_TAG);
        radix_tree_tag_set(&pag->pag_ici_root,
                           XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
                           XFS_ICI_EOFBLOCKS_TAG);
        if (!tagged) {
                /* propagate the eofblocks tag up into the perag radix tree */
                spin_lock(&ip->i_mount->m_perag_lock);
                radix_tree_tag_set(&ip->i_mount->m_perag_tree,
                                   XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
                                   XFS_ICI_EOFBLOCKS_TAG);
                spin_unlock(&ip->i_mount->m_perag_lock);

                /* kick off background trimming */
                xfs_queue_eofblocks(ip->i_mount);

                trace_xfs_perag_set_eofblocks(ip->i_mount, pag->pag_agno,
                                              -1, _RET_IP_);
        }

        spin_unlock(&pag->pag_ici_lock);
        xfs_perag_put(pag);
}

void
xfs_inode_clear_eofblocks_tag(
        xfs_inode_t     *ip)
{
        struct xfs_mount *mp = ip->i_mount;
        struct xfs_perag *pag;

        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
        spin_lock(&pag->pag_ici_lock);
        trace_xfs_inode_clear_eofblocks_tag(ip);

        radix_tree_tag_clear(&pag->pag_ici_root,
                             XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
                             XFS_ICI_EOFBLOCKS_TAG);
        if (!radix_tree_tagged(&pag->pag_ici_root, XFS_ICI_EOFBLOCKS_TAG)) {
                /* clear the eofblocks tag from the perag radix tree */
                spin_lock(&ip->i_mount->m_perag_lock);
                radix_tree_tag_clear(&ip->i_mount->m_perag_tree,
                                     XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
                                     XFS_ICI_EOFBLOCKS_TAG);
                spin_unlock(&ip->i_mount->m_perag_lock);
                trace_xfs_perag_clear_eofblocks(ip->i_mount, pag->pag_agno,
                                               -1, _RET_IP_);
        }

        spin_unlock(&pag->pag_ici_lock);
        xfs_perag_put(pag);
}