Btrfs: fix fallocate deadlock on inode extent lock

The btrfs fallocate call takes an extent lock on the entire range
being fallocated, and then runs through insert_reserved_extent on each
extent as they are allocated.

The problem with this is that btrfs_drop_extents may decide to try
and take the same extent lock fallocate was already holding.  The solution
used here is to push down knowledge of the range that is already locked
going into btrfs_drop_extents.

It turns out that at least one other caller had the same bug.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7594bec1be10..f4e5d2e5ece6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -830,7 +830,8 @@ static long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
         BUG_ON(!trans);
 
         /* punch hole in destination first */
-        btrfs_drop_extents(trans, root, inode, off, off+len, 0, &hint_byte);
+        btrfs_drop_extents(trans, root, inode, off, off + len,
+                           off + len, 0, &hint_byte);
 
         /* clone data */
         key.objectid = src->i_ino;