On Mon, Oct 10, 2016 at 05:24:38PM -0700, Song Liu wrote:

These are the 4th version of patches to 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 8 patches (details below).

Patch for chunk_aligned_read in earlier RFC is not included yet
(http://marc.info/?l=linux-raid&m=146432700719277). But we may still need
some optimizations later, especially for SSD raid devices.

Changes from PATCH v3 (http://marc.info/?l=linux-raid&m=147573807306070):
  1. Make reclaim robust
  2. Fix a bug in recovery

Changes between v3 and v2 (http://marc.info/?l=linux-raid&m=147493266208102):
  1. Incorporate feedback from Shaohua
  2. Reorganize the patches, for hopefully easier review
  3. Make sure no change to write through mode (journal only)
  4. Change reclaim design to avoid deadlock due to log space

Could you please add a test case for this in mdadm test suites?

Thanks,
Shaohua