Commit 8b41393f authored Oct 05, 2021 by Josef Bacik Committed by David Sterba Oct 26, 2021

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>

parent add9745a

fs/btrfs/volumes.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}