Re: [PATCH 0/2] btrfs: do most metadata parentnesss check at endio time

[David Sterba <dsterba@suse.cz>]

On Wed, Sep 14, 2022 at 01:32:49PM +0800, Qu Wenruo wrote:
> [BACKGROUND]
> 
> Btrfs metadata and data verification are both done at endio time.
> 
> But metadata has its own extra verifiaction, mostly related to
> parentness check, done at btrfs_read_extent_buffer() and
> read_tree_block().
> 
> This is not a big deal, but if we want to make metadata read-repair to
> share the same code base with data, we may want the metadata parentness
> check also to happen at endio time.
> 
> [ENHANCEMENT]
> 
> This patchset will move all the parentness check code into
> btrfs_validate_metadata_buffer().
> 
> As the first step, the first patch will concentrate all the existing
> parentness check into one structure.
> 
> Then the second patch will pass all the parentness info into btrfs_bio,
> using the shared space of data csum, so at endio time we can grab all
> the metadata parentness info and do the verification.
> 
> This means the following mismatch at read time would be rejected
> directly:
> 
> - First key mismatch
> - Transid mismatch
> - Level mismatch
> - Owner root mismatch
> 
> Since all the read-time parentness check is all done at endio now,
> btrfs_read_extent_buffer() can do less verification work for new extent
> buffers which is going to be read from disk.
> 
> But please note that, we still do parentness check for cached extent
> buffer, to avoid some cached/stale extent buffer read by other parent
> tree blocks to cause problems.
> 
> Thankfully that part will not trigger read repair thus won't affect us
> for now.
> 
> [TODO]
> Make metadata and data share the same code base to do read-repair.
> 
> The main blockage here is, we have a lot of pending patches changing
> the read-repair code, thus it's going to cause conflicts for the already
> lengthy pending patches.
> 
> Thus the refactor part is sent out first, then after read-repair is
> settled down, I can work on the unified read-repair code.
> 
> Qu Wenruo (2):
>   btrfs: concentrate all tree block parentness check parameters into one
>     structure
>   btrfs: move tree block parentness check into validate_extent_buffer()

As this is only 2 patches and they apply with minimal conflicts I've
added it to misc-next, thanks.