Messages in this thread | | | From | Ming Lin <> | Subject | [PATCH v3 00/11] simplify block layer based on immutable biovecs | Date | Wed, 6 May 2015 23:34:10 -0700 |
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v3: - rebase on top of 4.1-rc2 - support for QUEUE_FLAG_SG_GAPS - update commit logs of patch 2&4 - split bio for chunk_aligned_read
v2: https://lkml.org/lkml/2015/4/28/28 v1: https://lkml.org/lkml/2014/12/22/128
This is the 3rd attempt of simplifying block layer based on immutable biovecs. Immutable biovecs, implemented by Kent Overstreet, have been available in mainline since v3.14. Its original goal was actually making generic_make_request() accept arbitrarily sized bios, and pushing the splitting down to the drivers or wherever it's required. See also discussions in the past, [1] [2] [3].
This will bring not only performance improvements, but also a great amount of reduction in code complexity all over the block layer. Performance gain is possible due to the fact that bio_add_page() does not have to check unnecesary conditions such as queue limits or if biovecs are mergeable. Those will be delegated to the driver level. Kent already said that he actually benchmarked the impact of this with fio on a micron p320h, which showed definitely a positive impact.
Moreover, this patchset also allows a lot of code to be deleted, mainly because of removal of merge_bvec_fn() callbacks. We have been aware that it has been always a delicate issue for stacking block drivers (e.g. md and bcache) to handle merging bio consistently. This simplication will help every individual block driver avoid having such an issue.
Patches are against 4.1-rc1. These are also available in my git repo at:
https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=block-generic-req
This patchset is a prerequisite of other consecutive patchsets, e.g. multipage biovecs, rewriting plugging, or rewriting direct-IO, which are excluded this time. That means, this patchset should not bring any regression to end-users.
Comments are welcome. Ming
[1] https://lkml.org/lkml/2014/11/23/263 [2] https://lkml.org/lkml/2013/11/25/732 [3] https://lkml.org/lkml/2014/2/26/618
Dongsu Park (1): Documentation: update notes in biovecs about arbitrarily sized bios
Kent Overstreet (9): block: make generic_make_request handle arbitrarily sized bios block: simplify bio_add_page() block: allow __blk_queue_bounce() to handle bios larger than BIO_MAX_PAGES bcache: remove driver private bio splitting code btrfs: remove bio splitting and merge_bvec_fn() calls md/raid5: get rid of bio_fits_rdev() block: kill merge_bvec_fn() completely fs: use helper bio_add_page() instead of open coding on bi_io_vec md/raid10: make sync_request_write() call bio_copy_data()
Ming Lin (1): md/raid5: split bio for chunk_aligned_read
Documentation/block/biovecs.txt | 10 +- block/bio.c | 135 +++++++++++-------------- block/blk-core.c | 19 ++-- block/blk-merge.c | 148 ++++++++++++++++++++++++++-- block/blk-mq.c | 2 + block/blk-settings.c | 22 ----- block/bounce.c | 60 +++++++++-- drivers/block/drbd/drbd_int.h | 1 - drivers/block/drbd/drbd_main.c | 1 - drivers/block/drbd/drbd_req.c | 37 +------ drivers/block/pktcdvd.c | 27 +---- drivers/block/ps3vram.c | 2 + drivers/block/rbd.c | 47 --------- drivers/block/rsxx/dev.c | 2 + drivers/block/umem.c | 2 + drivers/block/zram/zram_drv.c | 2 + drivers/md/bcache/bcache.h | 18 ---- drivers/md/bcache/io.c | 100 +------------------ drivers/md/bcache/journal.c | 4 +- drivers/md/bcache/request.c | 16 +-- drivers/md/bcache/super.c | 32 +----- drivers/md/bcache/util.h | 5 +- drivers/md/bcache/writeback.c | 4 +- drivers/md/dm-cache-target.c | 21 ---- drivers/md/dm-crypt.c | 16 --- drivers/md/dm-era-target.c | 15 --- drivers/md/dm-flakey.c | 16 --- drivers/md/dm-linear.c | 16 --- drivers/md/dm-log-writes.c | 16 --- drivers/md/dm-snap.c | 15 --- drivers/md/dm-stripe.c | 21 ---- drivers/md/dm-table.c | 8 -- drivers/md/dm-thin.c | 31 ------ drivers/md/dm-verity.c | 16 --- drivers/md/dm.c | 122 +---------------------- drivers/md/dm.h | 2 - drivers/md/linear.c | 43 -------- drivers/md/md.c | 28 +----- drivers/md/md.h | 12 --- drivers/md/multipath.c | 21 ---- drivers/md/raid0.c | 56 ----------- drivers/md/raid0.h | 2 - drivers/md/raid1.c | 58 +---------- drivers/md/raid10.c | 139 ++------------------------ drivers/md/raid5.c | 97 +++++++----------- drivers/s390/block/dcssblk.c | 2 + drivers/s390/block/xpram.c | 2 + drivers/staging/lustre/lustre/llite/lloop.c | 2 + fs/btrfs/volumes.c | 72 -------------- fs/buffer.c | 7 +- fs/jfs/jfs_logmgr.c | 14 +-- include/linux/blkdev.h | 13 +-- include/linux/device-mapper.h | 4 - mm/page_io.c | 8 +- 54 files changed, 367 insertions(+), 1224 deletions(-)
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