commit 5f58d783fd7823b2c2d5954d1126e702f94bfc4c upstream

We have this check to make sure we don't accidentally add older devices that may have disappeared and re-appeared with an older generation from being added to an fs_devices (such as a replace source device). This makes sense, we don't want stale disks in our file system. However for single disks this doesn't really make sense.

I've seen this in testing, but I was provided a reproducer from a project that builds btrfs images on loopback devices. The loopback device gets cached with the new generation, and then if it is re-used to generate a new file system we'll fail to mount it because the new fs is "older" than what we have in cache.

Fix this by freeing the cache when closing the device for a single device filesystem. This will ensure that the mount command passed device path is scanned successfully during the next mount.

CC: stable@vger.kernel.org # 5.10+ Reported-by: Daan De Meyer daandemeyer@fb.com Signed-off-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Anand Jain anand.jain@oracle.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Anand Jain anand.jain@oracle.com --- This patch has already been submitted for the LTS stable 5.10 and above.

fs/btrfs/volumes.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 548de841cee5..dacaea61c2f7 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -354,6 +354,7 @@ void btrfs_free_device(struct btrfs_device *device) static void free_fs_devices(struct btrfs_fs_devices *fs_devices) { struct btrfs_device *device; + WARN_ON(fs_devices->opened); while (!list_empty(&fs_devices->devices)) { device = list_entry(fs_devices->devices.next, @@ -1401,6 +1402,17 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices) if (!fs_devices->opened) { seed_devices = fs_devices->seed; fs_devices->seed = NULL; + + /* + * If the struct btrfs_fs_devices is not assembled with any + * other device, it can be re-initialized during the next mount + * without the needing device-scan step. Therefore, it can be + * fully freed. + */ + if (fs_devices->num_devices == 1) { + list_del(&fs_devices->fs_list); + free_fs_devices(fs_devices); + } } mutex_unlock(&uuid_mutex);