[PATCH 0/6] Fix lockdep issues around device removal

[Josef Bacik <josef@toxicpanda.com>]

Hello,

The commit 87579e9b7d8d ("loop: use worker per cgroup instead of kworker")
enabled the use of workqueues for loopback devices, which brought with it
lockdep annotations for the workqueues for loopback devices.  This uncovered a
cascade of lockdep warnings because of how we mess with the block_device while
under the sb writers lock while doing the device removal.

The first patch seems innocuous but we have a lockdep_assert_held(&uuid_mutex)
in one of the helpers, which is why I have it first.  The code should never be
called which is why it is removed, but I'm removing it specifically to remove
confusion about the role of the uuid_mutex here.

The next 4 patches are to resolve the lockdep messages as they occur.  There are
several issues and I address them one at a time until we're no longer getting
lockdep warnings.

The final patch doesn't necessarily have to go in right away, it's just a
cleanup as I noticed we have a lot of duplicated code between the v1 and v2
device removal handling.  Thanks,

Josef

Josef Bacik (6):
  btrfs: do not check for ->num_devices == 0 in rm_device
  btrfs: do not take the uuid_mutex in btrfs_rm_device
  btrfs: do not read super look for a device path
  btrfs: update the bdev time directly when closing
  btrfs: delay blkdev_put until after the device remove
  btrfs: unify common code for the v1 and v2 versions of device remove

 fs/btrfs/ioctl.c   |  92 +++++++++++++++++--------------------
 fs/btrfs/volumes.c | 110 ++++++++++++++++++++-------------------------
 fs/btrfs/volumes.h |   3 +-
 3 files changed, 90 insertions(+), 115 deletions(-)

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2.26.3