From 602a6ae81383233c28d10a52bb4b3da56f72271e Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Tue, 27 Jul 2021 17:01:13 -0400 Subject: [PATCH] btrfs: do not call close_fs_devices in btrfs_rm_device There's a subtle case where if we're removing the seed device from a file system we need to free its private copy of the fs_devices. However we do not need to call close_fs_devices(), because at this point there are no devices left to close as we've closed the last one. The only thing that close_fs_devices() does is decrement ->opened, which should be 1. We want to avoid calling close_fs_devices() here because it has a lockdep_assert_held(&uuid_mutex), and we are going to stop holding the uuid_mutex in this path. So add an assert for the ->opened counter and simply decrement it like we should, and then clean up like normal. Also add a comment explaining what we're doing here as I initially removed this code erroneously. Signed-off-by: Josef Bacik Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 2101a5bd4eba8b..fd53c9483147bd 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2210,9 +2210,17 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, synchronize_rcu(); btrfs_free_device(device); + /* + * This can happen if cur_devices is the private seed devices list. We + * cannot call close_fs_devices() here because it expects the uuid_mutex + * to be held, but in fact we don't need that for the private + * seed_devices, we can simply decrement cur_devices->opened and then + * remove it from our list and free the fs_devices. + */ if (cur_devices->open_devices == 0) { + ASSERT(cur_devices->opened == 1); list_del_init(&cur_devices->seed_list); - close_fs_devices(cur_devices); + cur_devices->opened--; free_fs_devices(cur_devices); }