[PATCH v5 0/10] block: per-distpatch_queue flush machinery

From: Ming Lei
Date: Thu Sep 25 2014 - 11:26:50 EST


As recent discussion, especially suggested by Christoph, this patchset
implements per-distpatch_queue flush machinery, so that:

- current init_request and exit_request callbacks can
cover flush request too, then the buggy copying way of
initializing flush request's pdu can be fixed

- flushing performance gets improved in case of multi hw-queue

About 70% throughput improvement is observed in sync write
over multi dispatch-queue virtio-blk, see details in commit log
of patch 10/10.

This patchset can be pulled from below tree too:

git://kernel.ubuntu.com/ming/linux.git v3.17-block-dev-flush_v5

- make the failure path fix and cleanup patch as 1st one
- fix oops in case of bio based request queue(patch 6)
- pass 'node' to blk_alloc_flush_queue() instead of 'hctx'(patch 10)
- comment on init_request/exit_request about flush request(patch 10)

- remove pdu copy from original request to flush request
- don't call blk_free_flush_queue for !q->mq_ops

- don't return failure code from blk_alloc_flush_queue() to
avoid freeing invalid buffer in case of allocation failure
- remove blk_init_flush() and blk_exit_flush()
- remove unnecessary WARN_ON() from blk_alloc_flush_queue()
- refactor blk_mq_init_hw_queues() and its pair, also it is a fix
on failure path, so that conversion to per-queue flush becomes simple.
- allocate/initialize flush queue in blk_mq_init_hw_queues()
- add sync write tests on virtio-blk which is backed by SSD image

- commit log typo fix
- introduce blk_alloc_flush_queue() and its pair earlier, so
that patch 5 and 8 become easier for review

block/blk-core.c | 13 ++--
block/blk-flush.c | 141 +++++++++++++++++++++++++------------
block/blk-mq.c | 180 +++++++++++++++++++++++++++---------------------
block/blk-mq.h | 1 -
block/blk-sysfs.c | 4 +-
block/blk.h | 35 +++++++++-
include/linux/blk-mq.h | 6 ++
include/linux/blkdev.h | 10 +--
8 files changed, 246 insertions(+), 144 deletions(-)

Ming Lei

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