From 8b41393fe7c3b180abadc26856fb653014733bb9 Mon Sep 17 00:00:00 2001 From: Josef Bacik <josef@toxicpanda.com> Date: Tue, 5 Oct 2021 16:12:41 -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 simply decrement the ->opened counter 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. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com> --- 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 0941f61d8071..918ad3790791 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2211,9 +2211,17 @@ 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->num_devices == 0) { list_del_init(&cur_devices->seed_list); - close_fs_devices(cur_devices); + ASSERT(cur_devices->opened == 1); + cur_devices->opened--; free_fs_devices(cur_devices); } -- GitLab