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authorArne Jansen <sensille@gmx.net>2012-08-09 00:16:53 -0600
committerChris Mason <chris.mason@oracle.com>2012-08-28 16:53:35 -0400
commit22cd2e7de7b0bd68fb668d23e1564707ca689510 (patch)
tree115a0c4217ed00d1d879925928dd4e7395a599b2
parentb12a3b1ea209d9dec02731fba58c3dbe7d31cfd8 (diff)
Btrfs: fix race in run_clustered_refs
With commit commit d1270cd91f308c9d22b2804720c36ccd32dbc35e Author: Arne Jansen <sensille@gmx.net> Date: Tue Sep 13 15:16:43 2011 +0200 Btrfs: put back delayed refs that are too new I added a window where the delayed_ref's head->ref_mod code can diverge from the sum of the remaining refs, because we release the head->mutex in the middle. This leads to btrfs_lookup_extent_info returning wrong numbers. This patch fixes this by adjusting the head's ref_mod with each delayed ref we run. Signed-off-by: Arne Jansen <sensille@gmx.net> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
-rw-r--r--fs/btrfs/extent-tree.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1bb408f737f..f16411d3c25 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2318,6 +2318,23 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
ref->in_tree = 0;
rb_erase(&ref->rb_node, &delayed_refs->root);
delayed_refs->num_entries--;
+ if (locked_ref) {
+ /*
+ * when we play the delayed ref, also correct the
+ * ref_mod on head
+ */
+ switch (ref->action) {
+ case BTRFS_ADD_DELAYED_REF:
+ case BTRFS_ADD_DELAYED_EXTENT:
+ locked_ref->node.ref_mod -= ref->ref_mod;
+ break;
+ case BTRFS_DROP_DELAYED_REF:
+ locked_ref->node.ref_mod += ref->ref_mod;
+ break;
+ default:
+ WARN_ON(1);
+ }
+ }
spin_unlock(&delayed_refs->lock);
ret = run_one_delayed_ref(trans, root, ref, extent_op,