btrfs: raid56: extract the vertical stripe recovery code into recover_vertical()
This refactor includes the following behavior change first:
- Don't error out if only P/Q is corrupted
The old code will directly error out if only P/Q is corrupted.
Although it is an logical error if we go into rebuild path with
only P/Q corrupted, there is no need to error out.
Just skip the rebuild and return the already good data.
Then comes the following refactor which shouldn't cause behavior
changes:
- Introduce a helper to do vertical stripe recovery
This not only reduce one indent level, but also paves the road for
later data checksum verification in RMW cycles.
- Sort rbio->faila/b before recovery
So we don't need to do the same swap every vertical stripe
- Replace a BUG_ON() with ASSERT()
Or checkpatch won't let me pass.
- Mark recovered sectors uptodate after the recover loop
- Do the cleanup for pointers unconditionally
We only need to initialize @pointers and @unmap_array to NULL, so
we can safely free them unconditionally.
- Mark the repaired sector uptodate in recover_vertical()
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>