[PATCH v4 0/3] protect relocation with sb_start_write

[Naohiro Aota <naohiro.aota@wdc.com>]

This series is a follow-up to the series below [1]. The old series added
an assertion to btrfs_relocate_chunk() to check if it is protected
with sb_start_write(). However, it revealed another location we need
to add sb_start_write() [2].

Also, this series moved the ASSERT from btrfs_relocate_chunk() to
btrfs_relocate_block_group() because we do not need to call
sb_start_write() on a non-data block group [3].

[1] https://lore.kernel.org/linux-btrfs/cover.1645157220.git.naohiro.aota@wdc.com/T/

[2] https://lore.kernel.org/linux-btrfs/cover.1645157220.git.naohiro.aota@wdc.com/T/#e06eecc07ce1cd1e45bfd30a374bd2d15b4fd76d8

[3] https://lore.kernel.org/linux-btrfs/YjMSaLIhKNcKUuHM@debian9.Home/

Patch 1 adds sb_{start,end}_write() to the resumed async balancing.

Patches 2 and 3 add an ASSERT to catch a future error.

--
v4:
  - Fix subject of patch 2 (Filipe)
  - Revise the comment for the ASSERT (Filipe)
v3:
  - Only add sb_write_started(), which we really use. (Dave Chinner)
  - Drop patch "btrfs: mark device addition as mnt_want_write_file" (Filipe Manana)
  - Narrow asserting region to btrfs_relocate_block_group() and check only
    when the BG is data BG. (Filipe Manana)
v2:
  - Use mnt_want_write_file() instead of sb_start_write() for
    btrfs_ioctl_add_dev()
  - Drop bogus fixes tag
  - Change the stable target to meaningful 4.9+

Naohiro Aota (3):
  btrfs: mark resumed async balance as writing
  fs: add a check function for sb_start_write()
  btrfs: assert that relocation is protected with sb_start_write()

 fs/btrfs/relocation.c | 10 ++++++++++
 fs/btrfs/volumes.c    |  2 ++
 include/linux/fs.h    |  5 +++++
 3 files changed, 17 insertions(+)

-- 
2.35.1