Revert "dm: always call blk_queue_split() in dm_process_bio()"
This reverts commit
fc0e0e617ef118030bb4a809616510f0c82978dd.
blk_queue_split() is causing excessive IO splitting -- because
blk_max_size_offset() depends on 'chunk_sectors' limit being set and
if it isn't (as is the case for DM targets!) it falls back to
splitting on a 'max_sectors' boundary regardless of offset.
"Fix" this by reverting back to _not_ using blk_queue_split() in
dm_process_bio() for normal IO (reads and writes). Long-term fix is
still TBD but it should focus on training blk_max_size_offset() to
call into a DM provided hook (to call DM's max_io_len()).
Test results from simple misaligned IO test on 4-way dm-striped device
with chunksize of 128K and stripesize of 512K:
xfs_io -d -c 'pread -b 2m 224s 4072s' /dev/mapper/stripe_dev
before this revert:
253,0 21 1 0.
000000000 2206 Q R 224 + 4072 [xfs_io]
253,0 21 2 0.
000008267 2206 X R 224 / 480 [xfs_io]
253,0 21 3 0.
000010530 2206 X R 224 / 256 [xfs_io]
253,0 21 4 0.
000027022 2206 X R 480 / 736 [xfs_io]
253,0 21 5 0.
000028751 2206 X R 480 / 512 [xfs_io]
253,0 21 6 0.
000033323 2206 X R 736 / 992 [xfs_io]
253,0 21 7 0.
000035130 2206 X R 736 / 768 [xfs_io]
253,0 21 8 0.
000039146 2206 X R 992 / 1248 [xfs_io]
253,0 21 9 0.
000040734 2206 X R 992 / 1024 [xfs_io]
253,0 21 10 0.
000044694 2206 X R 1248 / 1504 [xfs_io]
253,0 21 11 0.
000046422 2206 X R 1248 / 1280 [xfs_io]
253,0 21 12 0.
000050376 2206 X R 1504 / 1760 [xfs_io]
253,0 21 13 0.
000051974 2206 X R 1504 / 1536 [xfs_io]
253,0 21 14 0.
000055881 2206 X R 1760 / 2016 [xfs_io]
253,0 21 15 0.
000057462 2206 X R 1760 / 1792 [xfs_io]
253,0 21 16 0.
000060999 2206 X R 2016 / 2272 [xfs_io]
253,0 21 17 0.
000062489 2206 X R 2016 / 2048 [xfs_io]
253,0 21 18 0.
000066133 2206 X R 2272 / 2528 [xfs_io]
253,0 21 19 0.
000067507 2206 X R 2272 / 2304 [xfs_io]
253,0 21 20 0.
000071136 2206 X R 2528 / 2784 [xfs_io]
253,0 21 21 0.
000072764 2206 X R 2528 / 2560 [xfs_io]
253,0 21 22 0.
000076185 2206 X R 2784 / 3040 [xfs_io]
253,0 21 23 0.
000077486 2206 X R 2784 / 2816 [xfs_io]
253,0 21 24 0.
000080885 2206 X R 3040 / 3296 [xfs_io]
253,0 21 25 0.
000082316 2206 X R 3040 / 3072 [xfs_io]
253,0 21 26 0.
000085788 2206 X R 3296 / 3552 [xfs_io]
253,0 21 27 0.
000087096 2206 X R 3296 / 3328 [xfs_io]
253,0 21 28 0.
000093469 2206 X R 3552 / 3808 [xfs_io]
253,0 21 29 0.
000095186 2206 X R 3552 / 3584 [xfs_io]
253,0 21 30 0.
000099228 2206 X R 3808 / 4064 [xfs_io]
253,0 21 31 0.
000101062 2206 X R 3808 / 3840 [xfs_io]
253,0 21 32 0.
000104956 2206 X R 4064 / 4096 [xfs_io]
253,0 21 33 0.
001138823 0 C R 4096 + 200 [0]
after this revert:
253,0 18 1 0.
000000000 4430 Q R 224 + 3896 [xfs_io]
253,0 18 2 0.
000018359 4430 X R 224 / 256 [xfs_io]
253,0 18 3 0.
000028898 4430 X R 256 / 512 [xfs_io]
253,0 18 4 0.
000033535 4430 X R 512 / 768 [xfs_io]
253,0 18 5 0.
000065684 4430 X R 768 / 1024 [xfs_io]
253,0 18 6 0.
000091695 4430 X R 1024 / 1280 [xfs_io]
253,0 18 7 0.
000098494 4430 X R 1280 / 1536 [xfs_io]
253,0 18 8 0.
000114069 4430 X R 1536 / 1792 [xfs_io]
253,0 18 9 0.
000129483 4430 X R 1792 / 2048 [xfs_io]
253,0 18 10 0.
000136759 4430 X R 2048 / 2304 [xfs_io]
253,0 18 11 0.
000152412 4430 X R 2304 / 2560 [xfs_io]
253,0 18 12 0.
000160758 4430 X R 2560 / 2816 [xfs_io]
253,0 18 13 0.
000183385 4430 X R 2816 / 3072 [xfs_io]
253,0 18 14 0.
000190797 4430 X R 3072 / 3328 [xfs_io]
253,0 18 15 0.
000197667 4430 X R 3328 / 3584 [xfs_io]
253,0 18 16 0.
000218751 4430 X R 3584 / 3840 [xfs_io]
253,0 18 17 0.
000226005 4430 X R 3840 / 4096 [xfs_io]
253,0 18 18 0.
000250404 4430 Q R 4120 + 176 [xfs_io]
253,0 18 19 0.
000847708 0 C R 4096 + 24 [0]
253,0 18 20 0.
000855783 0 C R 4120 + 176 [0]
Fixes: fc0e0e617ef1180 ("dm: always call blk_queue_split() in dm_process_bio()")
Cc: stable@vger.kernel.org
Reported-by: Andreas Gruenbacher <agruenba@redhat.com>
Tested-by: Barry Marson <bmarson@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
projects / kernel.git / commit