btrfs: introduce a new helper to submit write bio for repair
Both scrub and read-repair are utilizing a special repair writes that:
- Only writes back to a single device
Even for read-repair on RAID56, we only update the corrupted data
stripe itself, not triggering the full RMW path.
- Requires a valid @mirror_num
For RAID56 case, only @mirror_num == 1 is valid.
For non-RAID56 cases, we need @mirror_num to locate our stripe.
- No data csum generation needed
These two call sites still have some differences though:
- Read-repair goes plain bio
It doesn't need a full btrfs_bio, and goes submit_bio_wait().
- New scrub repair would go btrfs_bio
To simplify both read and write path.
So here this patch would:
- Introduce a common helper, btrfs_map_repair_block()
Due to the single device nature, we can use an on-stack
btrfs_io_stripe to pass device and its physical bytenr.
- Introduce a new interface, btrfs_submit_repair_bio(), for later scrub
code
This is for the incoming scrub code.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>