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

[Qu Wenruo <wqu@suse.com>]

BTW, since I have to re-run all the tests for every stable branch, for 
the stable branches and 5.18.x backports may be delayed a little.

In that case, I guess I should submit backports in the most recent 
stable branches first?

Thanks,
Qu

On 2022/8/19 15:01, Qu Wenruo wrote:
> 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(-)
>