From f2ddf0d4acb458679426733425760235730fbec9 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 31 May 2012 11:06:33 -0400 Subject: [PATCH] Btrfs: fix locking in btrfs_destroy_delayed_refs The transaction abort stuff was throwing warnings from the list debugging code because we do a list_del_init outside of the delayed_refs spin lock. The delayed refs locking makes baby Jesus cry so it's not hard to get wrong, but we need to take the ref head mutex to make sure it's not being processed currently, and so if it is we need to drop the spin lock and then take and drop the mutex and do the search again. If we can take the mutex then we can safely remove the head from the list and carry on. Now when the transaction aborts I don't get the list debugging warnings. Thanks, Signed-off-by: Josef Bacik --- fs/btrfs/disk-io.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index b99d5127ba189..c79ddc7560812 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -3400,7 +3400,6 @@ int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans, delayed_refs = &trans->delayed_refs; -again: spin_lock(&delayed_refs->lock); if (delayed_refs->num_entries == 0) { spin_unlock(&delayed_refs->lock); @@ -3408,31 +3407,36 @@ again: return ret; } - node = rb_first(&delayed_refs->root); - while (node) { + while ((node = rb_first(&delayed_refs->root)) != NULL) { ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node); - node = rb_next(node); - - ref->in_tree = 0; - rb_erase(&ref->rb_node, &delayed_refs->root); - delayed_refs->num_entries--; 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); - spin_unlock(&delayed_refs->lock); - mutex_lock(&head->mutex); + if (!mutex_trylock(&head->mutex)) { + atomic_inc(&ref->refs); + spin_unlock(&delayed_refs->lock); + + /* Need to wait for the delayed ref to run */ + mutex_lock(&head->mutex); + mutex_unlock(&head->mutex); + btrfs_put_delayed_ref(ref); + + continue; + } + kfree(head->extent_op); delayed_refs->num_heads--; if (list_empty(&head->cluster)) delayed_refs->num_heads_ready--; list_del_init(&head->cluster); - mutex_unlock(&head->mutex); - btrfs_put_delayed_ref(ref); - goto again; } + ref->in_tree = 0; + rb_erase(&ref->rb_node, &delayed_refs->root); + delayed_refs->num_entries--; + spin_unlock(&delayed_refs->lock); btrfs_put_delayed_ref(ref); -- 2.39.5