Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 21543bad authored by Filipe Manana's avatar Filipe Manana Committed by Chris Mason
Browse files

Btrfs: fix race when updating existing ref head 



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: default avatarFilipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent c3a46891

fs/btrfs/delayed-ref.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}