[PATCHv2 0/2] block: Discard merging fixes

[Keith Busch]

This series fixes some incorrect accounting from merging discard requests.

The first patch fixes merging two discard requests by having a special
case for merging these using the unique constraints discards have.

The second fixes merging a new discard bio into an existing
request. Previously all the schedulers defaulted to a front merge,
so the  patch just checks merge type and adds a 'case' for handling
discard in each of the callers.

I've only been able to test with mq-deadline on NVMe as that is the only
driver currently supporting multiple discard ranges in a single command.

v1 -> v2: 

  Fixed patch 1 based on feedback from Jens, tested with recreate
  sequence.

  Added 2nd patch for merging discard bios into existing requests.

Keith Busch (2):
  block: Merge discard requests as a special case
  block: Handle merging discards in IO schedulers

 block/bfq-iosched.c      |  2 +-
 block/blk-core.c         |  4 ++++
 block/blk-merge.c        | 29 ++++++++++++++++++++++++++++-
 block/blk-mq-sched.c     |  2 ++
 block/cfq-iosched.c      |  2 +-
 block/deadline-iosched.c |  4 +++-
 block/elevator.c         |  2 +-
 block/mq-deadline.c      |  2 +-
 8 files changed, 41 insertions(+), 6 deletions(-)

-- 
2.14.3