Btrfs: add nested locking mode for paths

This patch adds the possibilty to read-lock an extent even if it is already
write-locked from the same thread. btrfs_find_all_roots() needs this
capability.

Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index be1bf627a14b..dd8d140eb27b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3571,6 +3571,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
         atomic_set(&eb->blocking_writers, 0);
         atomic_set(&eb->spinning_readers, 0);
         atomic_set(&eb->spinning_writers, 0);
+        eb->lock_nested = 0;
         init_waitqueue_head(&eb->write_lock_wq);
         init_waitqueue_head(&eb->read_lock_wq);