[PATCH 0/4] btrfs: cleanups and preparation for the incoming RAID56J features

[Qu Wenruo <wqu@suse.com>]

Since I'm going to introduce two new chunk profiles, RAID5J and RAID6J
(J for journal), if we're relying on ad-hoc if () else if () branches to
calculate thing like number of p/q stripes, it will cause a lot of
problems.

In fact, during my development, I have hit tons of bugs related to this.

One example is alloc_rbio(), it will assign rbio->nr_data, if we forgot
to update the check for RAID5 and RAID6 profiles, we will got a bad
nr_data == num_stripes, and screw up later writeback.

90% of my suffering comes from such ad-hoc usage doing manual checks on
RAID56.

Another example is, scrub_stripe() which due to the extra per-device
reservation, @dev_extent_len is no longer the same the data stripe
length calculated from extent_map.

So this patchset will do the following cleanups preparing for the
incoming RAID56J (already finished coding, functionality and on-disk
format are fine, although no journal yet):

- Calculate device stripe length in-house inside scrub_stripe()
  This removes one of the nasty mismatch which is less obvious.

- Use btrfs_raid_array[] based calculation instead of ad-hoc check
  The only exception is scrub_nr_raid_mirrors(), which has several
  difference against btrfs_num_copies():

  * No iteration on all RAID6 combinations
    No sure if it's planned or not.

  * Use bioc->num_stripes directly
    In that context, bioc is already all the mirrors for the same
    stripe, thus no need to lookup using btrfs_raid_array[].

With all these cleanups, the RAID56J will be much easier to implement.

Qu Wenruo (4):
  btrfs: remove @dev_extent_len argument from scrub_stripe() function
  btrfs: use btrfs_chunk_max_errors() to replace weird tolerance
    calculation
  btrfs: use btrfs_raid_array[] to calculate the number of parity
    stripes
  btrfs: use btrfs_raid_array[].ncopies in btrfs_num_copies()

 fs/btrfs/raid56.c  | 10 ++--------
 fs/btrfs/raid56.h  | 12 ++----------
 fs/btrfs/scrub.c   | 13 +++++++------
 fs/btrfs/volumes.c | 35 +++++++++++++++++++++--------------
 fs/btrfs/volumes.h |  2 ++
 5 files changed, 34 insertions(+), 38 deletions(-)

-- 
2.36.1