[PATCH 0/5] raid5-cache: enabling cache features

[Song Liu <songliubraving@fb.com>]

These patches enable write cache part of raid5-cache. The journal part was
released with kernel 4.4.

The caching part uses same disk format of raid456 journal, and provides
acceleration to writes. Write operations are committed (bio_endio) once
the data is secured in journal. Reconstruct and RMW are postponed to
reclaim path, which is (hopefully) not on the critical path.

The changes are organized in 5 patches (details below). Current reclaim
approach can be improved. So far it works OK in my tests with spinning
disks as raid device and SSD as journal.

I removed the patch for chunk_aligned_read in earlier RFC
(http://marc.info/?l=linux-raid&m=146432700719277). But we may still need
some optimizations later, especially for SSD raid devices.

Thanks,
Song

Song Liu (5):
  r5cache: write part of r5cache
  r5cache: sysfs entry r5c_state
  r5cache: naive reclaim approach
  r5cache: r5c recovery
  r5cache: handle SYNC and FUA

 drivers/md/raid5-cache.c | 1299 ++++++++++++++++++++++++++++++++++++++++------
 drivers/md/raid5.c       |  185 ++++++-
 drivers/md/raid5.h       |   30 +-
 3 files changed, 1327 insertions(+), 187 deletions(-)

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2.8.0.rc2