commit 181490d532 upstream.
If bfq_schedule_dispatch() is called from bfq_idle_slice_timer_body(),
then 'bfqd->queued' is read without holding 'bfqd->lock'. This is
wrong since it can be wrote concurrently.
Fix the problem by holding 'bfqd->lock' in such case.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220513023507.2625717-2-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Khazhy Kumykov <khazhy@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 4e54a2493e upstream.
BFQ usage of __bio_blkcg() is a relict from the past. Furthermore if bio
would not be associated with any blkcg, the usage of __bio_blkcg() in
BFQ is prone to races with the task being migrated between cgroups as
__bio_blkcg() calls at different places could return different blkcgs.
Convert BFQ to the new situation where bio->bi_blkg is initialized in
bio_set_dev() and thus practically always valid. This allows us to save
blkcg_gq lookup and noticeably simplify the code.
CC: stable@vger.kernel.org
Fixes: 0fe061b9f0 ("blkcg: fix ref count issue with bio_blkcg() using task_css")
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-8-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 5f550ede5e upstream.
We call bfq_init_rq() from request merging functions where requests we
get should have already gone through bfq_init_rq() during insert and
anyway we want to do anything only if the request is already tracked by
BFQ. So replace calls to bfq_init_rq() with RQ_BFQQ() instead to simply
skip requests untracked by BFQ. We move bfq_init_rq() call in
bfq_insert_request() a bit earlier to cover request merging and thus
can transfer FIFO position in case of a merge.
CC: stable@vger.kernel.org
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-6-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit fc84e1f941 upstream.
In bfq_insert_request() we unlock bfqd->lock only to call
trace_block_rq_insert() and then lock bfqd->lock again. This is really
pointless since tracing is disabled if we really care about performance
and even if the tracepoint is enabled, it is a quick call.
CC: stable@vger.kernel.org
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-5-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit ea591cd4eb upstream.
When the process is migrated to a different cgroup (or in case of
writeback just starts submitting bios associated with a different
cgroup) bfq_merge_bio() can operate with stale cgroup information in
bic. Thus the bio can be merged to a request from a different cgroup or
it can result in merging of bfqqs for different cgroups or bfqqs of
already dead cgroups and causing possible use-after-free issues. Fix the
problem by updating cgroup information in bfq_merge_bio().
CC: stable@vger.kernel.org
Fixes: e21b7a0b98 ("block, bfq: add full hierarchical scheduling and cgroups support")
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-4-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 3bc5e683c6 upstream.
When bfqq is shared by multiple processes it can happen that one of the
processes gets moved to a different cgroup (or just starts submitting IO
for different cgroup). In case that happens we need to split the merged
bfqq as otherwise we will have IO for multiple cgroups in one bfqq and
we will just account IO time to wrong entities etc.
Similarly if the bfqq is scheduled to merge with another bfqq but the
merge didn't happen yet, cancel the merge as it need not be valid
anymore.
CC: stable@vger.kernel.org
Fixes: e21b7a0b98 ("block, bfq: add full hierarchical scheduling and cgroups support")
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-3-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit c1cee4ab36 upstream.
It can happen that the parent of a bfqq changes between the moment we
decide two queues are worth to merge (and set bic->stable_merge_bfqq)
and the moment bfq_setup_merge() is called. This can happen e.g. because
the process submitted IO for a different cgroup and thus bfqq got
reparented. It can even happen that the bfqq we are merging with has
parent cgroup that is already offline and going to be destroyed in which
case the merge can lead to use-after-free issues such as:
BUG: KASAN: use-after-free in __bfq_deactivate_entity+0x9cb/0xa50
Read of size 8 at addr ffff88800693c0c0 by task runc:[2:INIT]/10544
CPU: 0 PID: 10544 Comm: runc:[2:INIT] Tainted: G E 5.15.2-0.g5fb85fd-default #1 openSUSE Tumbleweed (unreleased) f1f3b891c72369aebecd2e43e4641a6358867c70
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0x46/0x5a
print_address_description.constprop.0+0x1f/0x140
? __bfq_deactivate_entity+0x9cb/0xa50
kasan_report.cold+0x7f/0x11b
? __bfq_deactivate_entity+0x9cb/0xa50
__bfq_deactivate_entity+0x9cb/0xa50
? update_curr+0x32f/0x5d0
bfq_deactivate_entity+0xa0/0x1d0
bfq_del_bfqq_busy+0x28a/0x420
? resched_curr+0x116/0x1d0
? bfq_requeue_bfqq+0x70/0x70
? check_preempt_wakeup+0x52b/0xbc0
__bfq_bfqq_expire+0x1a2/0x270
bfq_bfqq_expire+0xd16/0x2160
? try_to_wake_up+0x4ee/0x1260
? bfq_end_wr_async_queues+0xe0/0xe0
? _raw_write_unlock_bh+0x60/0x60
? _raw_spin_lock_irq+0x81/0xe0
bfq_idle_slice_timer+0x109/0x280
? bfq_dispatch_request+0x4870/0x4870
__hrtimer_run_queues+0x37d/0x700
? enqueue_hrtimer+0x1b0/0x1b0
? kvm_clock_get_cycles+0xd/0x10
? ktime_get_update_offsets_now+0x6f/0x280
hrtimer_interrupt+0x2c8/0x740
Fix the problem by checking that the parent of the two bfqqs we are
merging in bfq_setup_merge() is the same.
Link: https://lore.kernel.org/linux-block/20211125172809.GC19572@quack2.suse.cz/
CC: stable@vger.kernel.org
Fixes: 430a67f9d6 ("block, bfq: merge bursts of newly-created queues")
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-2-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 70456e5210 upstream.
bfq_setup_cooperator() can mark bic as stably merged even though it
decides to not merge its bfqqs (when bfq_setup_merge() returns NULL).
Make sure to mark bic as stably merged only if we are really going to
merge bfqqs.
CC: stable@vger.kernel.org
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Fixes: 430a67f9d6 ("block, bfq: merge bursts of newly-created queues")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit c5ac56bb61 ]
The code in bfq_check_waker() ignores wake up events from the current
waker. This makes it more likely we select a new tentative waker
although the current one is generating more wake up events. Treat
current waker the same way as any other process and allow it to reset
the waker detection logic.
Fixes: 71217df39d ("block, bfq: make waker-queue detection more robust")
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220519105235.31397-2-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit f950667356 ]
Currently we look for waker only if current queue has no requests. This
makes sense for bfq queues with a single process however for shared
queues when there is a larger number of processes the condition that
queue has no requests is difficult to meet because often at least one
process has some request in flight although all the others are waiting
for the waker to do the work and this harms throughput. Relax the "no
queued request for bfq queue" condition to "the current task has no
queued requests yet". For this, we also need to start tracking number of
requests in flight for each task.
This patch (together with the following one) restores the performance
for dbench with 128 clients that regressed with commit c65e6fd460
("bfq: Do not let waker requests skip proper accounting") because
this commit makes requests of wakers properly enter BFQ queues and thus
these queues become ineligible for the old waker detection logic.
Dbench results:
Vanilla 5.18-rc3 5.18-rc3 + revert 5.18-rc3 patched
Mean 1237.36 ( 0.00%) 950.16 * 23.21%* 988.35 * 20.12%*
Numbers are time to complete workload so lower is better.
Fixes: c65e6fd460 ("bfq: Do not let waker requests skip proper accounting")
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220519105235.31397-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 15729ff814 ]
A crash [1] happened to be triggered in conjunction with commit
2d52c58b9c ("block, bfq: honor already-setup queue merges"). The
latter was then reverted by commit ebc69e897e ("Revert "block, bfq:
honor already-setup queue merges""). Yet, the reverted commit was not
the one introducing the bug. In fact, it actually triggered a UAF
introduced by a different commit, and now fixed by commit d29bd41428
("block, bfq: reset last_bfqq_created on group change").
So, there is no point in keeping commit 2d52c58b9c ("block, bfq:
honor already-setup queue merges") out. This commit restores it.
[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503
Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20211125181510.15004-1-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit ab552fcb17 ]
KASAN reports a use-after-free report when doing normal scsi-mq test
[69832.239032] ==================================================================
[69832.241810] BUG: KASAN: use-after-free in bfq_dispatch_request+0x1045/0x44b0
[69832.243267] Read of size 8 at addr ffff88802622ba88 by task kworker/3:1H/155
[69832.244656]
[69832.245007] CPU: 3 PID: 155 Comm: kworker/3:1H Not tainted 5.10.0-10295-g576c6382529e #8
[69832.246626] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[69832.249069] Workqueue: kblockd blk_mq_run_work_fn
[69832.250022] Call Trace:
[69832.250541] dump_stack+0x9b/0xce
[69832.251232] ? bfq_dispatch_request+0x1045/0x44b0
[69832.252243] print_address_description.constprop.6+0x3e/0x60
[69832.253381] ? __cpuidle_text_end+0x5/0x5
[69832.254211] ? vprintk_func+0x6b/0x120
[69832.254994] ? bfq_dispatch_request+0x1045/0x44b0
[69832.255952] ? bfq_dispatch_request+0x1045/0x44b0
[69832.256914] kasan_report.cold.9+0x22/0x3a
[69832.257753] ? bfq_dispatch_request+0x1045/0x44b0
[69832.258755] check_memory_region+0x1c1/0x1e0
[69832.260248] bfq_dispatch_request+0x1045/0x44b0
[69832.261181] ? bfq_bfqq_expire+0x2440/0x2440
[69832.262032] ? blk_mq_delay_run_hw_queues+0xf9/0x170
[69832.263022] __blk_mq_do_dispatch_sched+0x52f/0x830
[69832.264011] ? blk_mq_sched_request_inserted+0x100/0x100
[69832.265101] __blk_mq_sched_dispatch_requests+0x398/0x4f0
[69832.266206] ? blk_mq_do_dispatch_ctx+0x570/0x570
[69832.267147] ? __switch_to+0x5f4/0xee0
[69832.267898] blk_mq_sched_dispatch_requests+0xdf/0x140
[69832.268946] __blk_mq_run_hw_queue+0xc0/0x270
[69832.269840] blk_mq_run_work_fn+0x51/0x60
[69832.278170] process_one_work+0x6d4/0xfe0
[69832.278984] worker_thread+0x91/0xc80
[69832.279726] ? __kthread_parkme+0xb0/0x110
[69832.280554] ? process_one_work+0xfe0/0xfe0
[69832.281414] kthread+0x32d/0x3f0
[69832.282082] ? kthread_park+0x170/0x170
[69832.282849] ret_from_fork+0x1f/0x30
[69832.283573]
[69832.283886] Allocated by task 7725:
[69832.284599] kasan_save_stack+0x19/0x40
[69832.285385] __kasan_kmalloc.constprop.2+0xc1/0xd0
[69832.286350] kmem_cache_alloc_node+0x13f/0x460
[69832.287237] bfq_get_queue+0x3d4/0x1140
[69832.287993] bfq_get_bfqq_handle_split+0x103/0x510
[69832.289015] bfq_init_rq+0x337/0x2d50
[69832.289749] bfq_insert_requests+0x304/0x4e10
[69832.290634] blk_mq_sched_insert_requests+0x13e/0x390
[69832.291629] blk_mq_flush_plug_list+0x4b4/0x760
[69832.292538] blk_flush_plug_list+0x2c5/0x480
[69832.293392] io_schedule_prepare+0xb2/0xd0
[69832.294209] io_schedule_timeout+0x13/0x80
[69832.295014] wait_for_common_io.constprop.1+0x13c/0x270
[69832.296137] submit_bio_wait+0x103/0x1a0
[69832.296932] blkdev_issue_discard+0xe6/0x160
[69832.297794] blk_ioctl_discard+0x219/0x290
[69832.298614] blkdev_common_ioctl+0x50a/0x1750
[69832.304715] blkdev_ioctl+0x470/0x600
[69832.305474] block_ioctl+0xde/0x120
[69832.306232] vfs_ioctl+0x6c/0xc0
[69832.306877] __se_sys_ioctl+0x90/0xa0
[69832.307629] do_syscall_64+0x2d/0x40
[69832.308362] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[69832.309382]
[69832.309701] Freed by task 155:
[69832.310328] kasan_save_stack+0x19/0x40
[69832.311121] kasan_set_track+0x1c/0x30
[69832.311868] kasan_set_free_info+0x1b/0x30
[69832.312699] __kasan_slab_free+0x111/0x160
[69832.313524] kmem_cache_free+0x94/0x460
[69832.314367] bfq_put_queue+0x582/0x940
[69832.315112] __bfq_bfqd_reset_in_service+0x166/0x1d0
[69832.317275] bfq_bfqq_expire+0xb27/0x2440
[69832.318084] bfq_dispatch_request+0x697/0x44b0
[69832.318991] __blk_mq_do_dispatch_sched+0x52f/0x830
[69832.319984] __blk_mq_sched_dispatch_requests+0x398/0x4f0
[69832.321087] blk_mq_sched_dispatch_requests+0xdf/0x140
[69832.322225] __blk_mq_run_hw_queue+0xc0/0x270
[69832.323114] blk_mq_run_work_fn+0x51/0x60
[69832.323942] process_one_work+0x6d4/0xfe0
[69832.324772] worker_thread+0x91/0xc80
[69832.325518] kthread+0x32d/0x3f0
[69832.326205] ret_from_fork+0x1f/0x30
[69832.326932]
[69832.338297] The buggy address belongs to the object at ffff88802622b968
[69832.338297] which belongs to the cache bfq_queue of size 512
[69832.340766] The buggy address is located 288 bytes inside of
[69832.340766] 512-byte region [ffff88802622b968, ffff88802622bb68)
[69832.343091] The buggy address belongs to the page:
[69832.344097] page:ffffea0000988a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88802622a528 pfn:0x26228
[69832.346214] head:ffffea0000988a00 order:2 compound_mapcount:0 compound_pincount:0
[69832.347719] flags: 0x1fffff80010200(slab|head)
[69832.348625] raw: 001fffff80010200 ffffea0000dbac08 ffff888017a57650 ffff8880179fe840
[69832.354972] raw: ffff88802622a528 0000000000120008 00000001ffffffff 0000000000000000
[69832.356547] page dumped because: kasan: bad access detected
[69832.357652]
[69832.357970] Memory state around the buggy address:
[69832.358926] ffff88802622b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[69832.360358] ffff88802622ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[69832.361810] >ffff88802622ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[69832.363273] ^
[69832.363975] ffff88802622bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
[69832.375960] ffff88802622bb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[69832.377405] ==================================================================
In bfq_dispatch_requestfunction, it may have function call:
bfq_dispatch_request
__bfq_dispatch_request
bfq_select_queue
bfq_bfqq_expire
__bfq_bfqd_reset_in_service
bfq_put_queue
kmem_cache_free
In this function call, in_serv_queue has beed expired and meet the
conditions to free. In the function bfq_dispatch_request, the address
of in_serv_queue pointing to has been released. For getting the value
of idle_timer_disabled, it will get flags value from the address which
in_serv_queue pointing to, then the problem of use-after-free happens;
Fix the problem by check in_serv_queue == bfqd->in_service_queue, to
get the value of idle_timer_disabled if in_serve_queue is equel to
bfqd->in_service_queue. If the space of in_serv_queue pointing has
been released, this judge will aviod use-after-free problem.
And if in_serv_queue may be expired or finished, the idle_timer_disabled
will be false which would not give effects to bfq_update_dispatch_stats.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Wensheng <zhangwensheng5@huawei.com>
Link: https://lore.kernel.org/r/20220303070334.3020168-1-zhangwensheng5@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit e92bc4cd34 upstream.
Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in
wbt_disable_default() when switch elevator to bfq. And when
we remove scsi device, wbt will be enabled by wbt_enable_default.
If it become false positive between wbt_wait() and wbt_track()
when submit write request.
The following is the scenario that triggered the problem.
T1 T2 T3
elevator_switch_mq
bfq_init_queue
wbt_disable_default <= Set
rwb->enable_state (OFF)
Submit_bio
blk_mq_make_request
rq_qos_throttle
<= rwb->enable_state (OFF)
scsi_remove_device
sd_remove
del_gendisk
blk_unregister_queue
elv_unregister_queue
wbt_enable_default
<= Set rwb->enable_state (ON)
q_qos_track
<= rwb->enable_state (ON)
^^^^^^ this request will mark WBT_TRACKED without inflight add and will
lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung.
Fix this by move wbt_enable_default() from elv_unregister to
bfq_exit_queue(). Only re-enable wbt when bfq exit.
Fixes: 76a8040817 ("blk-wbt: make sure throttle is enabled properly")
Remove oneline stale comment, and kill one oneshot local variable.
Signed-off-by: Ming Lei <ming.lei@rehdat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/linux-block/20211214133103.551813-1-qiulaibin@huawei.com/
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit c65e6fd460 ]
Commit 7cc4ffc555 ("block, bfq: put reqs of waker and woken in
dispatch list") added a condition to bfq_insert_request() which added
waker's requests directly to dispatch list. The rationale was that
completing waker's IO is needed to get more IO for the current queue.
Although this rationale is valid, there is a hole in it. The waker does
not necessarily serve the IO only for the current queue and maybe it's
current IO is not needed for current queue to make progress. Furthermore
injecting IO like this completely bypasses any service accounting within
bfq and thus we do not properly track how much service is waker's queue
getting or that the waker is actually doing any IO. Depending on the
conditions this can result in the waker getting too much or too few
service.
Consider for example the following job file:
[global]
directory=/mnt/repro/
rw=write
size=8g
time_based
runtime=30
ramp_time=10
blocksize=1m
direct=0
ioengine=sync
[slowwriter]
numjobs=1
prioclass=2
prio=7
fsync=200
[fastwriter]
numjobs=1
prioclass=2
prio=0
fsync=200
Despite processes have very different IO priorities, they get the same
about of service. The reason is that bfq identifies these processes as
having waker-wakee relationship and once that happens, IO from
fastwriter gets injected during slowwriter's time slice. As a result bfq
is not aware that fastwriter has any IO to do and constantly schedules
only slowwriter's queue. Thus fastwriter is forced to compete with
slowwriter's IO all the time instead of getting its share of time based
on IO priority.
Drop the special injection condition from bfq_insert_request(). As a
result, requests will be tracked and queued in a normal way and on next
dispatch bfq_select_queue() can decide whether the waker's inserted
requests should be injected during the current queue's timeslice or not.
Fixes: 7cc4ffc555 ("block, bfq: put reqs of waker and woken in dispatch list")
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211125133645.27483-8-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This reverts commit 2d52c58b9c.
We have had several folks complain that this causes hangs for them, which
is especially problematic as the commit has also hit stable already.
As no resolution seems to be forthcoming right now, revert the patch.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=214503
Fixes: 2d52c58b9c ("block, bfq: honor already-setup queue merges")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The function bfq_setup_merge prepares the merging between two
bfq_queues, say bfqq and new_bfqq. To this goal, it assigns
bfqq->new_bfqq = new_bfqq. Then, each time some I/O for bfqq arrives,
the process that generated that I/O is disassociated from bfqq and
associated with new_bfqq (merging is actually a redirection). In this
respect, bfq_setup_merge increases new_bfqq->ref in advance, adding
the number of processes that are expected to be associated with
new_bfqq.
Unfortunately, the stable-merging mechanism interferes with this
setup. After bfqq->new_bfqq has been set by bfq_setup_merge, and
before all the expected processes have been associated with
bfqq->new_bfqq, bfqq may happen to be stably merged with a different
queue than the current bfqq->new_bfqq. In this case, bfqq->new_bfqq
gets changed. So, some of the processes that have been already
accounted for in the ref counter of the previous new_bfqq will not be
associated with that queue. This creates an unbalance, because those
references will never be decremented.
This commit fixes this issue by reestablishing the previous, natural
behaviour: once bfqq->new_bfqq has been set, it will not be changed
until all expected redirections have occurred.
Signed-off-by: Davide Zini <davidezini2@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210802141352.74353-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace the magic lookup through the kobject tree with an explicit
backpointer, given that the device model links are set up and torn
down at times when I/O is still possible, leading to potential
NULL or invalid pointer dereferences.
Fixes: edb0872f44 ("block: move the bdi from the request_queue to the gendisk")
Reported-by: syzbot <syzbot+aa0801b6b32dca9dda82@syzkaller.appspotmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Link: https://lore.kernel.org/r/20210816134624.GA24234@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The default IO priority is the best effort (BE) class with the
normal priority level IOPRIO_NORM (4). However, get_task_ioprio()
returns IOPRIO_CLASS_NONE/IOPRIO_NORM as the default priority and
get_current_ioprio() returns IOPRIO_CLASS_NONE/0. Let's be consistent
with the defined default and have both of these functions return the
default priority IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM) when
the user did not define another default IO priority for the task.
In include/uapi/linux/ioprio.h, introduce the IOPRIO_BE_NORM macro as
an alias to IOPRIO_NORM to clarify that this default level applies to
the BE priotity class. In include/linux/ioprio.h, define the macro
IOPRIO_DEFAULT as IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM)
and use this new macro when setting a priority to the default.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210811033702.368488-7-damien.lemoal@wdc.com
[axboe: drop unnecessary lightnvm change]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The BFQ scheduler and ioprio_check_cap() both assume that the RT
priority class (IOPRIO_CLASS_RT) can have up to 8 different priority
levels, similarly to the BE class (IOPRIO_CLASS_iBE). This is
controlled using the IOPRIO_BE_NR macro , which is badly named as the
number of levels also applies to the RT class.
Introduce the class independent IOPRIO_NR_LEVELS macro, defined to 8,
to make things clear. Keep the old IOPRIO_BE_NR macro definition as an
alias for IOPRIO_NR_LEVELS.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210811033702.368488-6-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For a request that has a priority level equal to or larger than
IOPRIO_BE_NR, bfq_set_next_ioprio_data() prints a critical warning but
defaults to setting the request new_ioprio field to IOPRIO_BE_NR. This
is not consistent with the warning and the allowed values for priority
levels. Fix this by setting the request new_ioprio field to
IOPRIO_BE_NR - 1, the lowest priority level allowed.
Cc: <stable@vger.kernel.org>
Fixes: aee69d78de ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210811033702.368488-2-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When merging one bio to request, if they are discard IO and the queue
supports multi-range discard, we need to return ELEVATOR_DISCARD_MERGE
because both block core and related drivers(nvme, virtio-blk) doesn't
handle mixed discard io merge(traditional IO merge together with
discard merge) well.
Fix the issue by returning ELEVATOR_DISCARD_MERGE in this situation,
so both blk-mq and drivers just need to handle multi-range discard.
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Fixes: 2705dfb209 ("block: fix discard request merge")
Link: https://lore.kernel.org/r/20210729034226.1591070-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The backing device information only makes sense for file system I/O,
and thus belongs into the gendisk and not the lower level request_queue
structure. Move it there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210809141744.1203023-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Lockdep complains about lock inversion between ioc->lock and bfqd->lock:
bfqd -> ioc:
put_io_context+0x33/0x90 -> ioc->lock grabbed
blk_mq_free_request+0x51/0x140
blk_put_request+0xe/0x10
blk_attempt_req_merge+0x1d/0x30
elv_attempt_insert_merge+0x56/0xa0
blk_mq_sched_try_insert_merge+0x4b/0x60
bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed
blk_mq_sched_insert_requests+0xd6/0x2b0
blk_mq_flush_plug_list+0x154/0x280
blk_finish_plug+0x40/0x60
ext4_writepages+0x696/0x1320
do_writepages+0x1c/0x80
__filemap_fdatawrite_range+0xd7/0x120
sync_file_range+0xac/0xf0
ioc->bfqd:
bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed
put_io_context_active+0x78/0xb0 -> ioc->lock grabbed
exit_io_context+0x48/0x50
do_exit+0x7e9/0xdd0
do_group_exit+0x54/0xc0
To avoid this inversion we change blk_mq_sched_try_insert_merge() to not
free the merged request but rather leave that upto the caller similarly
to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure
to free all the merged requests after dropping bfqd->lock.
Fixes: aee69d78de ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210623093634.27879-3-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, bfq does very little in bfq_requests_merged() and handles all
the request cleanup in bfq_finish_requeue_request() called from
blk_mq_free_request(). That is currently safe only because
blk_mq_free_request() is called shortly after bfq_requests_merged()
while bfqd->lock is still held. However to fix a lock inversion between
bfqd->lock and ioc->lock, we need to call blk_mq_free_request() after
dropping bfqd->lock. That would mean that already merged request could
be seen by other processes inside bfq queues and possibly dispatched to
the device which is wrong. So move cleanup of the request from
bfq_finish_requeue_request() to bfq_requests_merged().
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210623093634.27879-2-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 85686d0dc1 ("block, bfq: keep shared queues out of the waker
mechanism") leaves shared bfq_queues out of the waker-detection
mechanism. It attains this goal by not updating the pointer
last_completed_rq_bfqq, if the last request completed belongs to a
shared bfq_queue (so that the pointer will not point to the shared
bfq_queue).
Yet this has a side effect: the pointer last_completed_rq_bfqq keeps
pointing, deceptively, to a bfq_queue that actually is not the last
one to have had a request completed. As a consequence, such a
bfq_queue may deceptively be considered as a waker of some bfq_queue,
even of some shared bfq_queue.
To address this issue, reset last_completed_rq_bfqq if the last
request completed belongs to a shared queue.
Fixes: 85686d0dc1 ("block, bfq: keep shared queues out of the waker mechanism")
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-8-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Consider two bfq_queues, say Q1 and Q2, with Q2 empty. If a request of
Q1 gets completed shortly before a new request arrives for Q2, then
BFQ flags Q1 as a candidate waker for Q2. Yet, the arrival of this new
request may have a different cause, in the following case. If also Q2
has requests in flight while waiting for the arrival of a new request,
then the completion of its own requests may be the actual cause of the
awakening of the process that sends I/O to Q2. So Q1 may be flagged
wrongly as a candidate waker.
This commit avoids this deceptive flagging, by disabling
candidate-waker flagging for Q2, if Q2 has in-flight I/O.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-7-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since commit 430a67f9d6 ("block, bfq: merge bursts of newly-created
queues"), BFQ may schedule a merge between a newly created sync
bfq_queue, say Q2, and the last sync bfq_queue created, say Q1. To this
goal, BFQ stores the address of Q1 in the field bic->stable_merge_bfqq
of the bic associated with Q2. So, when the time for the possible merge
arrives, BFQ knows which bfq_queue to merge Q2 with. In particular,
BFQ checks for possible merges on request arrivals.
Yet the same bic may also be associated with an async bfq_queue, say
Q3. So, if a request for Q3 arrives, then the above check may happen
to be executed while the bfq_queue at hand is Q3, instead of Q2. In
this case, Q1 happens to be merged with an async bfq_queue. This is
not only a conceptual mistake, because async queues are to be kept out
of queue merging, but also a bug that leads to inconsistent states.
This commits simply filters async queues out of delayed merges.
Fixes: 430a67f9d6 ("block, bfq: merge bursts of newly-created queues")
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-6-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
One of the methods with which bfq boosts throughput is by merging queues.
One of the merging variants in bfq is the stable merge.
This mechanism is activated between two queues only if they are created
within a certain maximum time T1 from each other.
Merging can happen soon or be delayed. In the second case, before
merging, bfq needs to evaluate a throughput-boost parameter that
indicates whether the queue generates a high throughput is served alone.
Merging occurs when this throughput-boost is not high enough.
In particular, this parameter is evaluated and late merging may occur
only after at least a time T2 from the creation of the queue.
Currently T1 and T2 are set to 180ms and 200ms, respectively.
In this way the merging mechanism rarely occurs because time is not
enough. This results in a noticeable lowering of the overall throughput
with some workloads (see the example below).
This commit introduces two constants bfq_activation_stable_merging and
bfq_late_stable_merging in order to increase the duration of T1 and T2.
Both the stable merging activation time and the late merging
time are set to 600ms. This value has been experimentally evaluated
using sqlite benchmark in the Phoronix Test Suite on a HDD.
The duration of the benchmark before this fix was 111.02s, while now
it has reached 97.02s, a better result than that of all the other
schedulers.
Signed-off-by: Pietro Pedroni <pedroni.pietro.96@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-5-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since commit 430a67f9d6 ("block, bfq: merge bursts of newly-created
queues"), BFQ may schedule a merge between a newly created sync
bfq_queue and the last sync bfq_queue created. Such a merging is not
performed immediately, because BFQ needs first to find out whether the
newly created queue actually reaches a higher throughput if not merged
at all (and in that case BFQ will not perform any stable merging). To
check that, a little time must be waited after the creation of the new
queue, so that some I/O can flow in the queue, and statistics on such
I/O can be computed.
Yet, to evaluate the above waiting time, the last split time is
considered as start time, instead of the creation time of the
queue. This is a mistake, because considering the split time is
correct only in the following scenario.
The queue undergoes a non-stable merges on the arrival of its very
first I/O request, due to close I/O with some other queue. While the
queue is merged for close I/O, stable merging is not considered. Yet
the queue may then happen to be split, if the close I/O finishes (or
happens to be a false positive). From this time on, the queue can
again be considered for stable merging. But, again, a little time must
elapse, to let some new I/O flow in the queue and to get updated
statistics. To wait for this time, the split time is to be taken into
account.
Yet, if the queue does not undergo a non-stable merge on the arrival
of its very first request, then BFQ immediately checks whether the
stable merge is to be performed. It happens because the split time for
a queue is initialized to minus infinity when the queue is created.
This commit fixes this mistake by adding the missing condition. Now
the check for delayed stable-merge is performed after a little time is
elapsed not only from the last queue split time, but also from the
creation time of the queue.
Fixes: 430a67f9d6 ("block, bfq: merge bursts of newly-created queues")
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-4-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When attempting to schedule a merge of a given bfq_queue with the currently
in-service bfq_queue or with a cooperating bfq_queue among the scheduled
bfq_queues, delayed stable merge is checked for rotational or non-queueing
devs. For this stable merge to be performed, some conditions must be met.
If the current bfq_queue underwent some split from some merged bfq_queue,
one of these conditions is that two hundred milliseconds must elapse from
split, otherwise this condition is always met.
Unfortunately, by mistake, time_is_after_jiffies() was written instead of
time_is_before_jiffies() for this check, verifying that less than two
hundred milliseconds have elapsed instead of verifying that at least two
hundred milliseconds have elapsed.
Fix this issue by replacing time_is_after_jiffies() with
time_is_before_jiffies().
Signed-off-by: Luca Mariotti <mariottiluca1@hotmail.it>
Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Pietro Pedroni <pedroni.pietro.96@gmail.com>
Link: https://lore.kernel.org/r/20210619140948.98712-3-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merged bfq_queues are kept out of weight-raising (low-latency)
mechanisms. The reason is that these queues are usually created for
non-interactive and non-soft-real-time tasks. Yet this is not the case
for stably-merged queues. These queues are merged just because they
are created shortly after each other. So they may easily serve the I/O
of an interactive or soft-real time application, if the application
happens to spawn multiple processes.
To address this issue, this commits lets also stably-merged queued
enjoy weight raising.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
BFQ may merge a new bfq_queue, stably, with the last bfq_queue
created. In particular, BFQ first waits a little bit for some I/O to
flow inside the new queue, say Q2, if this is needed to understand
whether it is better or worse to merge Q2 with the last queue created,
say Q1. This delayed stable merge is performed by assigning
bic->stable_merge_bfqq = Q1, for the bic associated with Q1.
Yet, while waiting for some I/O to flow in Q2, a non-stable queue
merge of Q2 with Q1 may happen, causing the bic previously associated
with Q2 to be associated with exactly Q1 (bic->bfqq = Q1). After that,
Q2 and Q1 may happen to be split, and, in the split, Q1 may happen to
be recycled as a non-shared bfq_queue. In that case, Q1 may then
happen to undergo a stable merge with the bfq_queue pointed by
bic->stable_merge_bfqq. Yet bic->stable_merge_bfqq still points to
Q1. So Q1 would be merged with itself.
This commit fixes this error by intercepting this situation, and
canceling the schedule of the stable merge.
Fixes: 430a67f9d6 ("block, bfq: merge bursts of newly-created queues")
Signed-off-by: Pietro Pedroni <pedroni.pietro.96@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210512094352.85545-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
__blk_mq_sched_bio_merge() gets the ctx and hctx for the current CPU and
passes the hctx to ->bio_merge(). kyber_bio_merge() then gets the ctx
for the current CPU again and uses that to get the corresponding Kyber
context in the passed hctx. However, the thread may be preempted between
the two calls to blk_mq_get_ctx(), and the ctx returned the second time
may no longer correspond to the passed hctx. This "works" accidentally
most of the time, but it can cause us to read garbage if the second ctx
came from an hctx with more ctx's than the first one (i.e., if
ctx->index_hw[hctx->type] > hctx->nr_ctx).
This manifested as this UBSAN array index out of bounds error reported
by Jakub:
UBSAN: array-index-out-of-bounds in ../kernel/locking/qspinlock.c:130:9
index 13106 is out of range for type 'long unsigned int [128]'
Call Trace:
dump_stack+0xa4/0xe5
ubsan_epilogue+0x5/0x40
__ubsan_handle_out_of_bounds.cold.13+0x2a/0x34
queued_spin_lock_slowpath+0x476/0x480
do_raw_spin_lock+0x1c2/0x1d0
kyber_bio_merge+0x112/0x180
blk_mq_submit_bio+0x1f5/0x1100
submit_bio_noacct+0x7b0/0x870
submit_bio+0xc2/0x3a0
btrfs_map_bio+0x4f0/0x9d0
btrfs_submit_data_bio+0x24e/0x310
submit_one_bio+0x7f/0xb0
submit_extent_page+0xc4/0x440
__extent_writepage_io+0x2b8/0x5e0
__extent_writepage+0x28d/0x6e0
extent_write_cache_pages+0x4d7/0x7a0
extent_writepages+0xa2/0x110
do_writepages+0x8f/0x180
__writeback_single_inode+0x99/0x7f0
writeback_sb_inodes+0x34e/0x790
__writeback_inodes_wb+0x9e/0x120
wb_writeback+0x4d2/0x660
wb_workfn+0x64d/0xa10
process_one_work+0x53a/0xa80
worker_thread+0x69/0x5b0
kthread+0x20b/0x240
ret_from_fork+0x1f/0x30
Only Kyber uses the hctx, so fix it by passing the request_queue to
->bio_merge() instead. BFQ and mq-deadline just use that, and Kyber can
map the queues itself to avoid the mismatch.
Fixes: a6088845c2 ("block: kyber: make kyber more friendly with merging")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/c7598605401a48d5cfeadebb678abd10af22b83f.1620691329.git.osandov@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since commit 01e99aeca3 'blk-mq: insert passthrough request into
hctx->dispatch directly', passthrough request should not appear in
IO-scheduler any more, so blk_rq_is_passthrough checking in addon IO
schedulers is redundant.
(Notes: this patch passes generic IO load test with hdds under SAS
controller and hdds under AHCI controller but obviously not covers all.
Not sure if passthrough request can still escape into IO scheduler from
blk_mq_sched_insert_requests, which is used by blk_mq_flush_plug_list and
has lots of indirect callers.)
Signed-off-by: Lin Feng <linf@wangsu.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Many throughput-sensitive workloads are made of several parallel I/O
flows, with all flows generated by the same application, or more
generically by the same task (e.g., system boot). The most
counterproductive action with these workloads is plugging I/O dispatch
when one of the bfq_queues associated with these flows remains
temporarily empty.
To avoid this plugging, BFQ has been using a burst-handling mechanism
for years now. This mechanism has proven effective for throughput, and
not detrimental for service guarantees. This commit pushes this
mechanism a little bit further, basing on the following two facts.
First, all the I/O flows of a the same application or task contribute
to the execution/completion of that common application or task. So the
performance figures that matter are total throughput of the flows and
task-wide I/O latency. In particular, these flows do not need to be
protected from each other, in terms of individual bandwidth or
latency.
Second, the above fact holds regardless of the number of flows.
Putting these two facts together, this commits merges stably the
bfq_queues associated with these I/O flows, i.e., with the processes
that generate these IO/ flows, regardless of how many the involved
processes are.
To decide whether a set of bfq_queues is actually associated with the
I/O flows of a common application or task, and to merge these queues
stably, this commit operates as follows: given a bfq_queue, say Q2,
currently being created, and the last bfq_queue, say Q1, created
before Q2, Q2 is merged stably with Q1 if
- very little time has elapsed since when Q1 was created
- Q2 has the same ioprio as Q1
- Q2 belongs to the same group as Q1
Merging bfq_queues also reduces scheduling overhead. A fio test with
ten random readers on /dev/nullb shows a throughput boost of 40%, with
a quadcore. Since BFQ's execution time amounts to ~50% of the total
per-request processing time, the above throughput boost implies that
BFQ's overhead is reduced by more than 50%.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-7-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Shared queues are likely to receive I/O at a high rate. This may
deceptively let them be considered as wakers of other queues. But a
false waker will unjustly steal bandwidth to its supposedly woken
queue. So considering also shared queues in the waking mechanism may
cause more control troubles than throughput benefits. This commit
keeps shared queues out of the waker-detection mechanism.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-6-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When the io_latency heuristic is off, bfq_queues must not start to be
weight-raised. Unfortunately, by mistake, this may happen when the
state of a previously weight-raised bfq_queue is resumed after a queue
split. This commit fixes this error.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-5-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Consider a bfq_queue bfqq that is about to be merged with another
bfq_queue new_bfqq. The processes associated with bfqq are cooperators
of the processes associated with new_bfqq. So, if bfqq has a waker,
then it is reasonable (and beneficial for throughput) to assume that
all these processes will be happy to let bfqq's waker freely inject
I/O when they have no I/O. So this commit makes new_bfqq inherit
bfqq's waker.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-4-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Consider a new I/O request that arrives for a bfq_queue bfqq. If, when
this happens, the only active bfq_queues are bfqq and either its waker
bfq_queue or one of its woken bfq_queues, then there is no point in
queueing this new I/O request in bfqq for service. In fact, the
in-service queue and bfqq agree on serving this new I/O request as
soon as possible. So this commit puts this new I/O request directly
into the dispatch list.
Tested-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-3-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Suppose that I/O dispatch is plugged, to wait for new I/O for the
in-service bfq-queue, say bfqq. Suppose then that there is a further
bfq_queue woken by bfqq, and that this woken queue has pending I/O. A
woken queue does not steal bandwidth from bfqq, because it remains
soon without I/O if bfqq is not served. So there is virtually no risk
of loss of bandwidth for bfqq if this woken queue has I/O dispatched
while bfqq is waiting for new I/O. In contrast, this extra I/O
injection boosts throughput. This commit performs this extra
injection.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Link: https://lore.kernel.org/r/20210304174627.161-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Correct the comments since bfq_fifo_expire[0] is for async request,
while bfq_fifo_expire[1] is for sync request.
Also update docs, according the source code, the default
fifo_expire_async is 250ms, and fifo_expire_sync is 125ms.
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Get rid of the wrapper for trace_block_rq_insert() and call the function
directly.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'for-5.12/block-2021-02-17' of git://git.kernel.dk/linux-block
Pull core block updates from Jens Axboe:
"Another nice round of removing more code than what is added, mostly
due to Christoph's relentless pursuit of tech debt removal/cleanups.
This pull request contains:
- Two series of BFQ improvements (Paolo, Jan, Jia)
- Block iov_iter improvements (Pavel)
- bsg error path fix (Pan)
- blk-mq scheduler improvements (Jan)
- -EBUSY discard fix (Jan)
- bvec allocation improvements (Ming, Christoph)
- bio allocation and init improvements (Christoph)
- Store bdev pointer in bio instead of gendisk + partno (Christoph)
- Block trace point cleanups (Christoph)
- hard read-only vs read-only split (Christoph)
- Block based swap cleanups (Christoph)
- Zoned write granularity support (Damien)
- Various fixes/tweaks (Chunguang, Guoqing, Lei, Lukas, Huhai)"
* tag 'for-5.12/block-2021-02-17' of git://git.kernel.dk/linux-block: (104 commits)
mm: simplify swapdev_block
sd_zbc: clear zone resources for non-zoned case
block: introduce blk_queue_clear_zone_settings()
zonefs: use zone write granularity as block size
block: introduce zone_write_granularity limit
block: use blk_queue_set_zoned in add_partition()
nullb: use blk_queue_set_zoned() to setup zoned devices
nvme: cleanup zone information initialization
block: document zone_append_max_bytes attribute
block: use bi_max_vecs to find the bvec pool
md/raid10: remove dead code in reshape_request
block: mark the bio as cloned in bio_iov_bvec_set
block: set BIO_NO_PAGE_REF in bio_iov_bvec_set
block: remove a layer of indentation in bio_iov_iter_get_pages
block: turn the nr_iovecs argument to bio_alloc* into an unsigned short
block: remove the 1 and 4 vec bvec_slabs entries
block: streamline bvec_alloc
block: factor out a bvec_alloc_gfp helper
block: move struct biovec_slab to bio.c
block: reuse BIO_INLINE_VECS for integrity bvecs
...
This reverts commit 6d4d273588.
bfq.limit_depth passes word_depths[] as shallow_depth down to sbitmap core
sbitmap_get_shallow, which uses just the number to limit the scan depth of
each bitmap word, formula:
scan_percentage_for_each_word = shallow_depth / (1 << sbimap->shift) * 100%
That means the comments's percentiles 50%, 75%, 18%, 37% of bfq are correct.
But after commit patch 'bfq: Fix computation of shallow depth', we use
sbitmap.depth instead, as a example in following case:
sbitmap.depth = 256, map_nr = 4, shift = 6; sbitmap_word.depth = 64.
The resulsts of computed bfqd->word_depths[] are {128, 192, 48, 96}, and
three of the numbers exceed core dirver's 'sbitmap_word.depth=64' limit
nothing.
Signed-off-by: Lin Feng <linf@wangsu.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently whenever bfq queue has a request queued we add now -
last_completion_time to the think time statistics. This is however
misleading in case the process is able to submit several requests in
parallel because e.g. if the queue has request completed at time T0 and
then queues new requests at times T1, T2, then we will add T1-T0 and
T2-T0 to think time statistics which just doesn't make any sence (the
queue's think time is penalized by the queue being able to submit more
IO). So add to think time statistics only time intervals when the queue
had no IO pending.
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
[axboe: fix whitespace on empty line]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use local variable 'ttime' instead of dereferencing bfqq.
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bfq_setup_cooperator() uses bfqd->in_serv_last_pos so detect whether it
makes sense to merge current bfq queue with the in-service queue.
However if the in-service queue is freshly scheduled and didn't dispatch
any requests yet, bfqd->in_serv_last_pos is stale and contains value
from the previously scheduled bfq queue which can thus result in a bogus
decision that the two queues should be merged. This bug can be observed
for example with the following fio jobfile:
[global]
direct=0
ioengine=sync
invalidate=1
size=1g
rw=read
[reader]
numjobs=4
directory=/mnt
where the 4 processes will end up in the one shared bfq queue although
they do IO to physically very distant files (for some reason I was able to
observe this only with slice_idle=1ms setting).
Fix the problem by invalidating bfqd->in_serv_last_pos when switching
in-service queue.
Fixes: 058fdecc6d ("block, bfq: fix in-service-queue check for queue merging")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's only used in the same file, mark is appropriately static.
Fixes: 71217df39d ("block, bfq: make waker-queue detection more robust")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In the presence of many parallel I/O flows, the detection of waker
bfq_queues suffers from false positives. This commits addresses this
issue by making the filtering of actual wakers more selective. In more
detail, a candidate waker must be found to meet waker requirements
three times before being promoted to actual waker.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
To prevent injection information from being lost on bfq_queue merging,
also the amount of service that a bfq_queue receives must be saved and
restored when the bfq_queue is merged and split, respectively.
Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Yu Kuai
Jan Kara
Paolo Valente
Zhang Wensheng
Laibin Qiu
Jens Axboe
Christoph Hellwig
Damien Le Moal
Ming Lei
Pietro Pedroni
Luca Mariotti
Omar Sandoval
Lin Feng
Joseph Qi
Chaitanya Kulkarni
Linus Torvalds