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[PATCH 2/3] xfs: convert inode shrinker to per-filesystem contexts

To: xfs@xxxxxxxxxxx
Subject: [PATCH 2/3] xfs: convert inode shrinker to per-filesystem contexts
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 15 Jul 2010 21:46:57 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx
In-reply-to: <1279194418-16119-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1279194418-16119-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

Now the shrinker passes us a context, wire up a shrinker context per
filesystem. This allows us to remove the global mount list and the
locking problems that introduced. It also means that a shrinker call
does not need to traverse clean filesystems before finding a
filesystem with reclaimable inodes.  This significantly reduces
scanning overhead when lots of filesystems are present.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/linux-2.6/xfs_super.c |    2 -
 fs/xfs/linux-2.6/xfs_sync.c  |   62 +++++++++--------------------------------
 fs/xfs/linux-2.6/xfs_sync.h  |    2 -
 fs/xfs/xfs_mount.h           |    2 +-
 4 files changed, 15 insertions(+), 53 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index f2d1718..80938c7 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1883,7 +1883,6 @@ init_xfs_fs(void)
                goto out_cleanup_procfs;
 
        vfs_initquota();
-       xfs_inode_shrinker_init();
 
        error = register_filesystem(&xfs_fs_type);
        if (error)
@@ -1911,7 +1910,6 @@ exit_xfs_fs(void)
 {
        vfs_exitquota();
        unregister_filesystem(&xfs_fs_type);
-       xfs_inode_shrinker_destroy();
        xfs_sysctl_unregister();
        xfs_cleanup_procfs();
        xfs_buf_terminate();
diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index be37582..f433819 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -828,14 +828,7 @@ xfs_reclaim_inodes(
 
 /*
  * 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(
        struct shrinker *shrink,
@@ -847,65 +840,38 @@ xfs_reclaim_inode_shrink(
        xfs_agnumber_t  ag;
        int             reclaimable = 0;
 
+       mp = container_of(shrink, struct xfs_mount, m_inode_shrink);
        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_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);
-       }
+               /* if we don't exhaust the scan, don't bother coming back */
+               if (nr_to_scan > 0)
+                       return -1;
+       }
 
-       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++) {
-                       pag = xfs_perag_get(mp, ag);
-                       reclaimable += pag->pag_ici_reclaimable;
-                       xfs_perag_put(pag);
-               }
+       for (ag = 0; ag < mp->m_sb.sb_agcount; ag++) {
+               pag = xfs_perag_get(mp, ag);
+               reclaimable += pag->pag_ici_reclaimable;
+               xfs_perag_put(pag);
        }
-       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);
+       mp->m_inode_shrink.shrink = xfs_reclaim_inode_shrink;
+       mp->m_inode_shrink.seeks = DEFAULT_SEEKS;
+       register_shrinker(&mp->m_inode_shrink);
 }
 
 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);
+       unregister_shrinker(&mp->m_inode_shrink);
 }
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index cdcbaac..e28139a 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -55,8 +55,6 @@ 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 write_lock, int *nr_to_scan);
 
-void xfs_inode_shrinker_init(void);
-void xfs_inode_shrinker_destroy(void);
 void xfs_inode_shrinker_register(struct xfs_mount *mp);
 void xfs_inode_shrinker_unregister(struct xfs_mount *mp);
 
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 1d2c7ee..5761087 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -259,7 +259,7 @@ typedef struct xfs_mount {
        wait_queue_head_t       m_wait_single_sync_task;
        __int64_t               m_update_flags; /* sb flags we need to update
                                                   on the next remount,rw */
-       struct list_head        m_mplist;       /* inode shrinker mount list */
+       struct shrinker         m_inode_shrink; /* inode reclaim shrinker */
 } xfs_mount_t;
 
 /*
-- 
1.7.1

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