From: Filipe David Borba Manana <fdmanana@gmail.com>
To: linux-btrfs@vger.kernel.org
Cc: Filipe David Borba Manana <fdmanana@gmail.com>
Subject: [PATCH] Btrfs: fix race when updating existing ref head
Date: Fri, 14 Mar 2014 20:55:01 +0000 [thread overview]
Message-ID: <1394830501-24550-1-git-send-email-fdmanana@gmail.com> (raw)
While we update an existing ref head's extent_op, we're not holding
its spinlock, so while we're updating its extent_op contents (key,
flags) we can have a task running __btrfs_run_delayed_refs() that
holds the ref head's lock and sets its extent_op to NULL right after
the task updating the ref head just checked its extent_op was not NULL.
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
---
fs/btrfs/delayed-ref.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index 2502ba5..3129964 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -495,6 +495,7 @@ update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
ref = btrfs_delayed_node_to_head(update);
BUG_ON(existing_ref->is_data != ref->is_data);
+ spin_lock(&existing_ref->lock);
if (ref->must_insert_reserved) {
/* if the extent was freed and then
* reallocated before the delayed ref
@@ -536,7 +537,6 @@ update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
* only need the lock for this case cause we could be processing it
* currently, for refs we just added we know we're a-ok.
*/
- spin_lock(&existing_ref->lock);
existing->ref_mod += update->ref_mod;
spin_unlock(&existing_ref->lock);
}
--
1.7.9.5
reply other threads:[~2014-03-14 20:55 UTC|newest]
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