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>
---
Changes v1->v2:
Changed commit message. As Josef pointed out the race is new and has
not been present before d1270cd9. The code is unchanged.
---
fs/btrfs/extent-tree.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e66dc9a..60d175a 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,
--
1.7.7.3
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