[PATCH] Btrfs: fix lock leak when resuming snapshot deletion

[PATCH] Btrfs: fix lock leak when resuming snapshot deletion

[Josef Bacik]

We aren't setting path->locks[level] when we resume a snapshot deletion which
means we won't unlock the buffer when we free the path.  This causes deadlocks
if we happen to re-allocate the block before we've evicted the extent buffer
from cache.  Thanks,

Reported-by: Alex Lyakas <alex.btrfs@zadarastorage.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
 fs/btrfs/extent-tree.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8c204e1..997a5dd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7555,6 +7555,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 		while (1) {
 			btrfs_tree_lock(path->nodes[level]);
 			btrfs_set_lock_blocking(path->nodes[level]);
+			path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
 
 			ret = btrfs_lookup_extent_info(trans, root,
 						path->nodes[level]->start,
@@ -7570,6 +7571,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 				break;
 
 			btrfs_tree_unlock(path->nodes[level]);
+			path->locks[level] = 0;
 			WARN_ON(wc->refs[level] != 1);
 			level--;
 		}
-- 
1.7.7.6

Re: [PATCH] Btrfs: fix lock leak when resuming snapshot deletion

[Alex Lyakas]

On Mon, Jul 15, 2013 at 7:43 PM, Josef Bacik <jbacik@fusionio.com> wrote:
> We aren't setting path->locks[level] when we resume a snapshot deletion which
> means we won't unlock the buffer when we free the path.  This causes deadlocks
> if we happen to re-allocate the block before we've evicted the extent buffer
> from cache.  Thanks,
>
> Reported-by: Alex Lyakas <alex.btrfs@zadarastorage.com>
> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
> ---
>  fs/btrfs/extent-tree.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 8c204e1..997a5dd 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -7555,6 +7555,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
>                 while (1) {
>                         btrfs_tree_lock(path->nodes[level]);
>                         btrfs_set_lock_blocking(path->nodes[level]);
> +                       path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
>
>                         ret = btrfs_lookup_extent_info(trans, root,
>                                                 path->nodes[level]->start,
> @@ -7570,6 +7571,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
>                                 break;
>
>                         btrfs_tree_unlock(path->nodes[level]);
> +                       path->locks[level] = 0;
>                         WARN_ON(wc->refs[level] != 1);
>                         level--;
>                 }
> --
> 1.7.7.6
>
> --

Tested-by: Liran Strugano <liran@zadarastorage.com>

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