From eb12db690c7eb0f6593ba5792f5861409e88bc03 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Wed, 30 Jan 2013 16:03:59 -0500 Subject: [PATCH] Btrfs: fix freeing delayed ref head while still holding its mutex I hit this error when reproducing a bug that would end in a transaction abort. We take the delayed ref head's mutex to keep anybody from processing it while we're destroying it, but we fail to drop the mutex before we carry on and free the damned thing. Fix this by doing the remove logic for the head ourselves and unlock the mutex, that way we can avoid use after free's or hung tasks waiting on that mutex to come back so they know the delayed ref completed. Thanks, Signed-off-by: Josef Bacik --- fs/btrfs/disk-io.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index bd48bf2..8140cb0 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -3615,11 +3615,11 @@ int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans, } while ((node = rb_first(&delayed_refs->root)) != NULL) { - ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node); + struct btrfs_delayed_ref_head *head = NULL; + ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node); atomic_set(&ref->refs, 1); if (btrfs_delayed_ref_is_head(ref)) { - struct btrfs_delayed_ref_head *head; head = btrfs_delayed_node_to_head(ref); if (!mutex_trylock(&head->mutex)) { @@ -3641,10 +3641,12 @@ int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans, delayed_refs->num_heads_ready--; list_del_init(&head->cluster); } + ref->in_tree = 0; rb_erase(&ref->rb_node, &delayed_refs->root); delayed_refs->num_entries--; - + if (head) + mutex_unlock(&head->mutex); spin_unlock(&delayed_refs->lock); btrfs_put_delayed_ref(ref); -- 2.7.4