3 files changed, 33 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 754bc591a247..37d33254981d 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -837,8 +837,12 @@ xfs_reclaim_inodes_ag(
         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;
@@ -846,6 +850,15 @@ xfs_reclaim_inodes_ag(
 
                 ag = pag->pag_agno + 1;
 
+                if (trylock) {
+                        if (!mutex_trylock(&pag->pag_ici_reclaim_lock)) {
+                                skipped++;
+                                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;
@@ -898,8 +911,25 @@ xfs_reclaim_inodes_ag(
 
                 } 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 (trylock && skipped && *nr_to_scan > 0) {
+                trylock = 0;
+                goto restart;
+        }
         return XFS_ERROR(last_error);
 }
 
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 51c42c202bf1..baeec83d01f9 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -230,6 +230,8 @@ typedef struct xfs_perag {
         rwlock_t        pag_ici_lock;   /* incore inode lock */
         struct radix_tree_root pag_ici_root;    /* incore inode cache root */
         int             pag_ici_reclaimable;    /* reclaimable inodes */
+        struct mutex    pag_ici_reclaim_lock;   /* serialisation point */
+        unsigned long   pag_ici_reclaim_cursor; /* reclaim restart point */
 
         /* for rcu-safe freeing */
         struct rcu_head rcu_head;
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index d66e87c7c3a6..59859c343e04 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -477,6 +477,7 @@ xfs_initialize_perag(
                 pag->pag_agno = index;
                 pag->pag_mount = mp;
                 rwlock_init(&pag->pag_ici_lock);
+                mutex_init(&pag->pag_ici_reclaim_lock);
                 INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
 
                 if (radix_tree_preload(GFP_NOFS))