[PATCH STABLE 5.19 0/2] btrfs: raid56: backports to reduce corruption

[Qu Wenruo <wqu@suse.com>]

This backport is going to address the following possible corruption for
btrfs RAID56:

- RMW always writes the full P/Q stripe
  This happens even only some vertical stripes are dirty.

  If some data sectors are corrupted in the clean vertical stripes,
  then such unnecessary P/Q updates will wipe the chance or recovery,
  as the P/Q will be calculated using corrupted data.

  This will be addressed by the first backport patch.

- Don't trust any cached sector when doing recovery
  Although above patch will avoid unnecessary P/Q writes, the full P/Q
  stripe will still be updated in the in-memory only RAID56 cache.

  To properly recovery data stripes, we should not trust any cached
  sector, and always read data from disk, which will avoid corrupted
  P/Q sectors.

  This will be addressed by the second backport patch.

This would make some previously always-fail test cases, like btrfs/125,
to pass, and end users have a lower chance to corrupt their RAID56 data.

Since this is a data corruption related fix, these backport patches are
needed for all stable branches.

Unfortunately due to the new cleanups in v6.0-rc, these backport patches
have quite some conflicts (even for 5.19), and have to be manually resolved.
Almost every stable branch will need their own backports.

Acked-by: David Sterba <dsterba@suse.com>

Qu Wenruo (2):
  btrfs: only write the sectors in the vertical stripe which has data
    stripes
  btrfs: raid56: don't trust any cached sector in
    __raid56_parity_recover()

 fs/btrfs/raid56.c | 68 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 55 insertions(+), 13 deletions(-)

-- 
2.37.1