Fix evict() deadlock

[zfs.git] / module / zfs / zfs_znode.c

diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index 1017414..1fe8849 100644 (file)
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -980,13 +980,24 @@ zfs_zinactive(znode_t *zp)
 {
        zfs_sb_t *zsb = ZTOZSB(zp);
        uint64_t z_id = zp->z_id;
+       boolean_t drop_mutex = 0;
 
        ASSERT(zp->z_sa_hdl);
 
        /*
-        * Don't allow a zfs_zget() while were trying to release this znode
+        * Don't allow a zfs_zget() while were trying to release this znode.
+        *
+        * Linux allows direct memory reclaim which means that any KM_SLEEP
+        * allocation may trigger inode eviction.  This can lead to a deadlock
+        * through the ->shrink_icache_memory()->evict()->zfs_inactive()->
+        * zfs_zinactive() call path.  To avoid this deadlock the process
+        * must not reacquire the mutex when it is already holding it.
         */
-       ZFS_OBJ_HOLD_ENTER(zsb, z_id);
+       if (!ZFS_OBJ_HOLD_OWNED(zsb, z_id)) {
+               ZFS_OBJ_HOLD_ENTER(zsb, z_id);
+               drop_mutex = 1;
+       }
+
        mutex_enter(&zp->z_lock);
 
        /*
@@ -995,14 +1006,19 @@ zfs_zinactive(znode_t *zp)
         */
        if (zp->z_unlinked) {
                mutex_exit(&zp->z_lock);
-               ZFS_OBJ_HOLD_EXIT(zsb, z_id);
+
+               if (drop_mutex)
+                       ZFS_OBJ_HOLD_EXIT(zsb, z_id);
+
                zfs_rmnode(zp);
                return;
        }
 
        mutex_exit(&zp->z_lock);
        zfs_znode_dmu_fini(zp);
-       ZFS_OBJ_HOLD_EXIT(zsb, z_id);
+
+       if (drop_mutex)
+               ZFS_OBJ_HOLD_EXIT(zsb, z_id);
 }
 
 void