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Paolo Valente 058fdecc6d block, bfq: fix in-service-queue check for queue merging 
When a new I/O request arrives for a bfq_queue, say Q, bfq checks
whether that request is close to
(a) the head request of some other queue waiting to be served, or
(b) the last request dispatched for the in-service queue (in case Q
itself is not the in-service queue)

If a queue, say Q2, is found for which the above condition holds, then
bfq merges Q and Q2, to hopefully get a more sequential I/O in the
resulting merged queue, and thus a possibly higher throughput.

Case (b) is checked by comparing the new request for Q with the last
request dispatched, assuming that the latter necessarily belonged to the
in-service queue. Unfortunately, this assumption is no longer always
correct, since commit d0edc2473b ("block, bfq: inject other-queue I/O
into seeky idle queues on NCQ flash").

When the assumption does not hold, queues that must not be merged may be
merged, causing unexpected loss of control on per-queue service
guarantees.

This commit solves this problem by adding an extra field, which stores
the actual last request dispatched for the in-service queue, and by
using this new field to correctly check case (b).

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
 		2019-01-31 12:50:24 -07:00
..
partitions partitions/aix: append null character to print data from disk 2018-07-27 09:17:41 -06:00
Kconfig Kconfig updates for v4.21 2018-12-29 13:03:29 -08:00
Kconfig.iosched block: remove legacy IO schedulers 2018-11-07 13:42:32 -07:00
Makefile block: remove legacy IO schedulers 2018-11-07 13:42:32 -07:00
badblocks.c badblocks: fix wrong return value in badblocks_set if badblocks are disabled 2017-11-03 11:29:50 -07:00
bfq-cgroup.c blkcg: fix ref count issue with bio_blkcg() using task_css 2018-12-07 22:26:36 -07:00
bfq-iosched.c block, bfq: fix in-service-queue check for queue merging 2019-01-31 12:50:24 -07:00
bfq-iosched.h block, bfq: fix in-service-queue check for queue merging 2019-01-31 12:50:24 -07:00
bfq-wf2q.c block, bfq: fix queue removal from weights tree 2019-01-31 12:50:24 -07:00
bio-integrity.c block: remove the bio_integrity_advance export 2018-12-16 08:33:57 -07:00
bio.c for-4.21/block-20190102 2019-01-02 18:49:58 -08:00
blk-cgroup.c blkcg: remove unused __blkg_release_rcu() 2018-12-21 08:47:58 -07:00
blk-core.c Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED" 2019-01-27 06:35:28 -07:00
blk-exec.c block: remove dead elevator code 2018-11-07 13:42:32 -07:00
blk-flush.c block: add queue_is_mq() helper 2018-11-16 08:34:06 -07:00
blk-integrity.c block: merge BIOVEC_SEG_BOUNDARY into biovec_phys_mergeable 2018-09-24 12:33:57 -06:00
blk-ioc.c block: remove the queue_lock indirection 2018-11-15 12:17:28 -07:00
blk-iolatency.c block: fix blk-iolatency accounting underflow 2018-12-17 11:19:54 -07:00
blk-lib.c block: fix 32 bit overflow in __blkdev_issue_discard() 2018-11-14 08:17:18 -07:00
blk-map.c Merge branch 'for-4.16/block' of git://git.kernel.dk/linux-block 2018-01-29 11:51:49 -08:00
blk-merge.c Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED" 2019-01-27 06:35:28 -07:00
blk-mq-cpumap.c blk-mq: initial support for multiple queue maps 2018-11-07 13:45:00 -07:00
blk-mq-debugfs-zoned.c block: Cleanup license notice 2019-01-17 21:21:40 -07:00
blk-mq-debugfs.c blk-mq: fix the cmd_flag_name array 2019-01-24 08:41:42 -07:00
blk-mq-debugfs.h blk-mq-debugfs: support rq_qos 2018-12-16 19:53:47 -07:00
blk-mq-pci.c blk-mq: initial support for multiple queue maps 2018-11-07 13:45:00 -07:00
blk-mq-rdma.c blk-mq-rdma: pass in queue map to blk_mq_rdma_map_queues 2018-12-13 09:59:08 +01:00
blk-mq-sched.c blk-mq: fix dispatch from sw queue 2018-12-17 11:19:54 -07:00
blk-mq-sched.h block: mq-deadline: Fix write completion handling 2018-12-17 11:19:39 -07:00
blk-mq-sysfs.c blk-mq: export hctx->type in debugfs instead of sysfs 2018-12-17 05:44:45 -07:00
blk-mq-tag.c sbitmap: optimize wakeup check 2018-11-30 14:48:04 -07:00
blk-mq-tag.h Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
blk-mq-virtio.c blk-mq: initial support for multiple queue maps 2018-11-07 13:45:00 -07:00
blk-mq.c block: don't lose track of REQ_INTEGRITY flag 2019-01-16 07:28:10 -07:00
blk-mq.h blk-mq: fix dispatch from sw queue 2018-12-17 11:19:54 -07:00
blk-pm.c block: remove the queue_lock indirection 2018-11-15 12:17:28 -07:00
blk-pm.h block: remove the queue_lock indirection 2018-11-15 12:17:28 -07:00
blk-rq-qos.c blk-mq-debugfs: support rq_qos 2018-12-16 19:53:47 -07:00
blk-rq-qos.h block: fix blk-iolatency accounting underflow 2018-12-17 11:19:54 -07:00
blk-settings.c SCSI misc on 20181224 2018-12-28 14:48:06 -08:00
blk-softirq.c block: remove a few unused exports 2018-11-15 12:13:25 -07:00
blk-stat.c block: remove a few unused exports 2018-11-15 12:13:25 -07:00
blk-stat.h block: deactivate blk_stat timer in wbt_disable_default() 2018-12-12 06:47:51 -07:00
blk-sysfs.c SCSI misc on 20181224 2018-12-28 14:48:06 -08:00
blk-throttle.c blkcg: consolidate bio_issue_init() to be a part of core 2018-12-07 22:26:37 -07:00
blk-timeout.c block: don't hold the queue_lock over blk_abort_request 2018-11-15 12:13:18 -07:00
blk-wbt.c blk-wbt: Declare local functions static 2019-01-24 11:09:21 -07:00
blk-wbt.h block: remove external dependency on wbt_flags 2018-07-09 09:07:54 -06:00
blk-zoned.c for-4.21/block-20181221 2018-12-28 13:19:59 -08:00
blk.h block: sum requests in the plug structure 2018-11-26 10:35:22 -07:00
bounce.c blkcg: remove bio->bi_css and instead use bio->bi_blkg 2018-12-07 22:26:37 -07:00
bsg-lib.c bsg: move bsg-lib parts outside of request queue 2018-11-07 13:42:33 -07:00
bsg.c bsg: deprecate BIDI support in bsg 2018-12-21 08:47:58 -07:00
cmdline-parser.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat_ioctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
elevator.c block: add queue_is_mq() helper 2018-11-16 08:34:06 -07:00
genhd.c block: return just one value from part_in_flight 2018-12-10 08:30:38 -07:00
ioctl.c block: Introduce BLKGETNRZONES ioctl 2018-10-25 11:17:40 -06:00
ioprio.c block: add ioprio_check_cap function 2018-05-31 10:50:54 -04:00
kyber-iosched.c kyber: use sbitmap add_wait_queue/list_del wait helpers 2018-12-20 12:17:21 -07:00
mq-deadline.c block: mq-deadline: Fix write completion handling 2018-12-17 11:19:39 -07:00
opal_proto.h block: sed-opal: Set MBRDone on S3 resume path if TPER is MBREnabled 2017-09-11 09:45:52 -06:00
partition-generic.c block: return just one value from part_in_flight 2018-12-10 08:30:38 -07:00
scsi_ioctl.c block: consistently use GFP_NOIO instead of __GFP_NORECLAIM 2018-05-14 08:55:18 -06:00
sed-opal.c block: sed-opal: Fix a couple off by one bugs 2018-06-20 12:04:06 -06:00
t10-pi.c block: move dif_prepare/dif_complete functions to block layer 2018-07-30 08:27:02 -06:00