Btrfs: unlock extent range on enospc in compressed submit

A user reported a deadlock where the async submit thread was blocked on the
lock_extent() lock, and then everybody behind him was locked on the page lock
for the page he was holding.  Looking at the code I noticed we do not unlock the
extent range when we get ENOSPC and goto retry.  This is bad because we
immediately try to lock that range again to do the cow, which will cause a
deadlock.  Fix this by unlocking the range.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a2df4690b000d852efdb680d6f75510f36d407dd..509112da6118de97476f381e4d691f66812b75a4 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -700,8 +700,12 @@ retry:
                        async_extent->nr_pages = 0;
                        async_extent->pages = NULL;
 
-                       if (ret == -ENOSPC)
+                       if (ret == -ENOSPC) {
+                               unlock_extent(io_tree, async_extent->start,
+                                             async_extent->start +
+                                             async_extent->ram_size - 1);
                                goto retry;
+                       }
                        goto out_free;
                }