linux-stable.git/block, branch v4.19.82

blk-rq-qos: fix first node deletion of rq_qos_del()

2019-10-29T08:20:09+00:00

commit 307f4065b9d7c1e887e8bdfb2487e4638559fea1 upstream.

rq_qos_del() incorrectly assigns the node being deleted to the head if
it was the first on the list in the !prev path.  Fix it by iterating
with ** instead.

Signed-off-by: Tejun Heo 
Cc: Josef Bacik 
Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

blk-wbt: fix performance regression in wbt scale_up/scale_down

2019-10-17T20:45:16+00:00

commit b84477d3ebb96294f87dc3161e53fa8fe22d9bfd upstream.

scale_up wakes up waiters after scaling up. But after scaling max, it
should not wake up more waiters as waiters will not have anything to
do. This patch fixes this by making scale_up (and also scale_down)
return when threshold is reached.

This bug causes increased fdatasync latency when fdatasync and dd
conv=sync are performed in parallel on 4.19 compared to 4.14. This
bug was introduced during refactoring of blk-wbt code.

Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt")
Cc: stable@vger.kernel.org
Cc: Josef Bacik 
Signed-off-by: Harshad Shirwadkar 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

block: mq-deadline: Fix queue restart handling

2019-10-07T16:57:19+00:00

[ Upstream commit cb8acabbe33b110157955a7425ee876fb81e6bbc ]

Commit 7211aef86f79 ("block: mq-deadline: Fix write completion
handling") added a call to blk_mq_sched_mark_restart_hctx() in
dd_dispatch_request() to make sure that write request dispatching does
not stall when all target zones are locked. This fix left a subtle race
when a write completion happens during a dispatch execution on another
CPU:

CPU 0: Dispatch			CPU1: write completion

dd_dispatch_request()
    lock(&dd->lock);
    ...
    lock(&dd->zone_lock);	dd_finish_request()
    rq = find request		lock(&dd->zone_lock);
    unlock(&dd->zone_lock);
    				zone write unlock
				unlock(&dd->zone_lock);
				...
				__blk_mq_free_request
                                      check restart flag (not set)
				      -> queue not run
    ...
    if (!rq && have writes)
        blk_mq_sched_mark_restart_hctx()
    unlock(&dd->lock)

Since the dispatch context finishes after the write request completion
handling, marking the queue as needing a restart is not seen from
__blk_mq_free_request() and blk_mq_sched_restart() not executed leading
to the dispatch stall under 100% write workloads.

Fix this by moving the call to blk_mq_sched_mark_restart_hctx() from
dd_dispatch_request() into dd_finish_request() under the zone lock to
ensure full mutual exclusion between write request dispatch selection
and zone unlock on write request completion.

Fixes: 7211aef86f79 ("block: mq-deadline: Fix write completion handling")
Cc: stable@vger.kernel.org
Reported-by: Hans Holmberg 
Reviewed-by: Hans Holmberg 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Damien Le Moal 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

block: fix null pointer dereference in blk_mq_rq_timed_out()

2019-10-05T11:10:08+00:00

commit 8d6996630c03d7ceeabe2611378fea5ca1c3f1b3 upstream.

We got a null pointer deference BUG_ON in blk_mq_rq_timed_out()
as following:

[  108.825472] BUG: kernel NULL pointer dereference, address: 0000000000000040
[  108.827059] PGD 0 P4D 0
[  108.827313] Oops: 0000 [#1] SMP PTI
[  108.827657] CPU: 6 PID: 198 Comm: kworker/6:1H Not tainted 5.3.0-rc8+ #431
[  108.829503] Workqueue: kblockd blk_mq_timeout_work
[  108.829913] RIP: 0010:blk_mq_check_expired+0x258/0x330
[  108.838191] Call Trace:
[  108.838406]  bt_iter+0x74/0x80
[  108.838665]  blk_mq_queue_tag_busy_iter+0x204/0x450
[  108.839074]  ? __switch_to_asm+0x34/0x70
[  108.839405]  ? blk_mq_stop_hw_queue+0x40/0x40
[  108.839823]  ? blk_mq_stop_hw_queue+0x40/0x40
[  108.840273]  ? syscall_return_via_sysret+0xf/0x7f
[  108.840732]  blk_mq_timeout_work+0x74/0x200
[  108.841151]  process_one_work+0x297/0x680
[  108.841550]  worker_thread+0x29c/0x6f0
[  108.841926]  ? rescuer_thread+0x580/0x580
[  108.842344]  kthread+0x16a/0x1a0
[  108.842666]  ? kthread_flush_work+0x170/0x170
[  108.843100]  ret_from_fork+0x35/0x40

The bug is caused by the race between timeout handle and completion for
flush request.

When timeout handle function blk_mq_rq_timed_out() try to read
'req->q->mq_ops', the 'req' have completed and reinitiated by next
flush request, which would call blk_rq_init() to clear 'req' as 0.

After commit 12f5b93145 ("blk-mq: Remove generation seqeunce"),
normal requests lifetime are protected by refcount. Until 'rq->ref'
drop to zero, the request can really be free. Thus, these requests
cannot been reused before timeout handle finish.

However, flush request has defined .end_io and rq->end_io() is still
called even if 'rq->ref' doesn't drop to zero. After that, the 'flush_rq'
can be reused by the next flush request handle, resulting in null
pointer deference BUG ON.

We fix this problem by covering flush request with 'rq->ref'.
If the refcount is not zero, flush_end_io() return and wait the
last holder recall it. To record the request status, we add a new
entry 'rq_status', which will be used in flush_end_io().

Cc: Christoph Hellwig 
Cc: Keith Busch 
Cc: Bart Van Assche 
Cc: stable@vger.kernel.org # v4.18+
Reviewed-by: Ming Lei 
Reviewed-by: Bob Liu 
Signed-off-by: Yufen Yu 
Signed-off-by: Greg Kroah-Hartman 

-------
v2:
 - move rq_status from struct request to struct blk_flush_queue
v3:
 - remove unnecessary '{}' pair.
v4:
 - let spinlock to protect 'fq->rq_status'
v5:
 - move rq_status after flush_running_idx member of struct blk_flush_queue
Signed-off-by: Jens Axboe

blk-mq: move cancel of requeue_work to the front of blk_exit_queue

2019-10-01T06:26:10+00:00

[ Upstream commit e26cc08265dda37d2acc8394604f220ef412299d ]

blk_exit_queue will free elevator_data, while blk_mq_requeue_work
will access it. Move cancel of requeue_work to the front of
blk_exit_queue to avoid use-after-free.

blk_exit_queue                blk_mq_requeue_work
  __elevator_exit               blk_mq_run_hw_queues
    blk_mq_exit_sched             blk_mq_run_hw_queue
      dd_exit_queue                 blk_mq_hctx_has_pending
        kfree(elevator_data)          blk_mq_sched_has_work
                                        dd_has_work

Fixes: fbc2a15e3433 ("blk-mq: move cancel of requeue_work into blk_mq_release")
Cc: stable@vger.kernel.org
Reviewed-by: Ming Lei 
Signed-off-by: zhengbin 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

blk-mq: change gfp flags to GFP_NOIO in blk_mq_realloc_hw_ctxs

2019-10-01T06:26:10+00:00

[ Upstream commit 5b202853ffbc54b29f23c4b1b5f3948efab489a2 ]

blk_mq_realloc_hw_ctxs could be invoked during update hw queues.
At the momemt, IO is blocked. Change the gfp flags from GFP_KERNEL
to GFP_NOIO to avoid forever hang during memory allocation in
blk_mq_realloc_hw_ctxs.

Signed-off-by: Jianchao Wang 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

blk-mq: free hw queue's resource in hctx's release handler

2019-09-16T06:22:13+00:00

[ Upstream commit c7e2d94b3d1634988a95ac4d77a72dc7487ece06 ]

Once blk_cleanup_queue() returns, tags shouldn't be used any more,
because blk_mq_free_tag_set() may be called. Commit 45a9c9d909b2
("blk-mq: Fix a use-after-free") fixes this issue exactly.

However, that commit introduces another issue. Before 45a9c9d909b2,
we are allowed to run queue during cleaning up queue if the queue's
kobj refcount is held. After that commit, queue can't be run during
queue cleaning up, otherwise oops can be triggered easily because
some fields of hctx are freed by blk_mq_free_queue() in blk_cleanup_queue().

We have invented ways for addressing this kind of issue before, such as:

	8dc765d438f1 ("SCSI: fix queue cleanup race before queue initialization is done")
	c2856ae2f315 ("blk-mq: quiesce queue before freeing queue")

But still can't cover all cases, recently James reports another such
kind of issue:

	https://marc.info/?l=linux-scsi&m=155389088124782&w=2

This issue can be quite hard to address by previous way, given
scsi_run_queue() may run requeues for other LUNs.

Fixes the above issue by freeing hctx's resources in its release handler, and this
way is safe becasue tags isn't needed for freeing such hctx resource.

This approach follows typical design pattern wrt. kobject's release handler.

Cc: Dongli Zhang 
Cc: James Smart 
Cc: Bart Van Assche 
Cc: linux-scsi@vger.kernel.org,
Cc: Martin K . Petersen ,
Cc: Christoph Hellwig ,
Cc: James E . J . Bottomley ,
Reported-by: James Smart 
Fixes: 45a9c9d909b2 ("blk-mq: Fix a use-after-free")
Cc: stable@vger.kernel.org
Reviewed-by: Hannes Reinecke 
Reviewed-by: Christoph Hellwig 
Tested-by: James Smart 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

blk-iolatency: fix STS_AGAIN handling

2019-09-16T06:21:41+00:00

[ Upstream commit c9b3007feca018d3f7061f5d5a14cb00766ffe9b ]

The iolatency controller is based on rq_qos. It increments on
rq_qos_throttle() and decrements on either rq_qos_cleanup() or
rq_qos_done_bio(). a3fb01ba5af0 fixes the double accounting issue where
blk_mq_make_request() may call both rq_qos_cleanup() and
rq_qos_done_bio() on REQ_NO_WAIT. So checking STS_AGAIN prevents the
double decrement.

The above works upstream as the only way we can get STS_AGAIN is from
blk_mq_get_request() failing. The STS_AGAIN handling isn't a real
problem as bio_endio() skipping only happens on reserved tag allocation
failures which can only be caused by driver bugs and already triggers
WARN.

However, the fix creates a not so great dependency on how STS_AGAIN can
be propagated. Internally, we (Facebook) carry a patch that kills read
ahead if a cgroup is io congested or a fatal signal is pending. This
combined with chained bios progagate their bi_status to the parent is
not already set can can cause the parent bio to not clean up properly
even though it was successful. This consequently leaks the inflight
counter and can hang all IOs under that blkg.

To nip the adverse interaction early, this removes the rq_qos_cleanup()
callback in iolatency in favor of cleaning up always on the
rq_qos_done_bio() path.

Fixes: a3fb01ba5af0 ("blk-iolatency: only account submitted bios")
Debugged-by: Tejun Heo 
Debugged-by: Josef Bacik 
Signed-off-by: Dennis Zhou 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

Blk-iolatency: warn on negative inflight IO counter

2019-09-16T06:21:41+00:00

[ Upstream commit 391f552af213985d3d324c60004475759a7030c5 ]

This is to catch any unexpected negative value of inflight IO counter.

Signed-off-by: Liu Bo 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

block, bfq: handle NULL return value by bfq_init_rq()

2019-08-29T06:28:46+00:00

[ Upstream commit fd03177c33b287c6541f4048f1d67b7b45a1abc9 ]

As reported in [1], the call bfq_init_rq(rq) may return NULL in case
of OOM (in particular, if rq->elv.icq is NULL because memory
allocation failed in failed in ioc_create_icq()).

This commit handles this circumstance.

[1] https://lkml.org/lkml/2019/7/22/824

Cc: Hsin-Yi Wang 
Cc: Nicolas Boichat 
Cc: Doug Anderson 
Reported-by: Guenter Roeck 
Reported-by: Hsin-Yi Wang 
Reviewed-by: Guenter Roeck 
Signed-off-by: Paolo Valente 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin