| Message ID | 20171016232905.5047-10-bart.vanassche@wdc.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Mon, Oct 16, 2017 at 04:29:04PM -0700, Bart Van Assche wrote: > The contexts from which a SCSI device can be quiesced or resumed are: > * Writing into /sys/class/scsi_device/*/device/state. > * SCSI parallel (SPI) domain validation. > * The SCSI device power management methods. See also scsi_bus_pm_ops. > > It is essential during suspend and resume that neither the filesystem > state nor the filesystem metadata in RAM changes. This is why while > the hibernation image is being written or restored that SCSI devices > are quiesced. The SCSI core quiesces devices through scsi_device_quiesce() > and scsi_device_resume(). In the SDEV_QUIESCE state execution of > non-preempt requests is deferred. This is realized by returning > BLKPREP_DEFER from inside scsi_prep_state_check() for quiesced SCSI > devices. Avoid that a full queue prevents power management requests > to be submitted by deferring allocation of non-preempt requests for > devices in the quiesced state. This patch has been tested by running > the following commands and by verifying that after resume the fio job > is still running: > > for d in /sys/class/block/sd*[a-z]; do > hcil=$(readlink "$d/device") > hcil=${hcil#../../../} > echo 4 > "$d/queue/nr_requests" > echo 1 > "/sys/class/scsi_device/$hcil/device/queue_depth" > done > bdev=$(readlink /dev/disk/by-uuid/5217d83f-213e-4b42-b86e-20013325ba6c) > bdev=${bdev#../../} > hcil=$(readlink "/sys/block/$bdev/device") > hcil=${hcil#../../../} > fio --name="$bdev" --filename="/dev/$bdev" --buffered=0 --bs=512 --rw=randread \ > --ioengine=libaio --numjobs=4 --iodepth=16 --iodepth_batch=1 --thread \ > --loops=$((2**31)) & > pid=$! > sleep 1 > systemctl hibernate > sleep 10 > kill $pid > > Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name> > References: "I/O hangs after resuming from suspend-to-ram" (https://marc.info/?l=linux-block&m=150340235201348). > Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> > Tested-by: Martin Steigerwald <martin@lichtvoll.de> > Cc: Martin K. Petersen <martin.petersen@oracle.com> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Hannes Reinecke <hare@suse.com> > Cc: Johannes Thumshirn <jthumshirn@suse.de> > --- > block/blk-core.c | 42 +++++++++++++++++++++++++++++++++++------- > block/blk-mq.c | 4 ++-- > block/blk-timeout.c | 2 +- > drivers/scsi/scsi_lib.c | 40 +++++++++++++++++++++++++++++----------- > fs/block_dev.c | 4 ++-- > include/linux/blkdev.h | 2 +- > include/scsi/scsi_device.h | 1 + > 7 files changed, 71 insertions(+), 24 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index b73203286bf5..abb5095bcef6 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -372,6 +372,7 @@ void blk_clear_preempt_only(struct request_queue *q) > > spin_lock_irqsave(q->queue_lock, flags); > queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q); > + wake_up_all(&q->mq_freeze_wq); > spin_unlock_irqrestore(q->queue_lock, flags); > } > EXPORT_SYMBOL_GPL(blk_clear_preempt_only); > @@ -793,15 +794,40 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask) > } > EXPORT_SYMBOL(blk_alloc_queue); > > -int blk_queue_enter(struct request_queue *q, bool nowait) > +/** > + * blk_queue_enter() - try to increase q->q_usage_counter > + * @q: request queue pointer > + * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PREEMPT > + */ > +int blk_queue_enter(struct request_queue *q, unsigned int flags) > { > + const bool preempt = flags & BLK_MQ_REQ_PREEMPT; > + > while (true) { > + bool success = false; > int ret; > > - if (percpu_ref_tryget_live(&q->q_usage_counter)) > + rcu_read_lock_sched(); > + if (percpu_ref_tryget_live(&q->q_usage_counter)) { > + /* > + * The code that sets the PREEMPT_ONLY flag is > + * responsible for ensuring that that flag is globally > + * visible before the queue is unfrozen. > + */ > + if (preempt || !blk_queue_preempt_only(q)) { > + success = true; > + } else { > + percpu_ref_put(&q->q_usage_counter); > + WARN_ONCE("%s: Attempt to allocate non-preempt request in preempt-only mode.\n", > + kobject_name(q->kobj.parent)); > + } > + } > + rcu_read_unlock_sched(); > + > + if (success) > return 0; > > - if (nowait) > + if (flags & BLK_MQ_REQ_NOWAIT) > return -EBUSY; > > /* > @@ -814,7 +840,8 @@ int blk_queue_enter(struct request_queue *q, bool nowait) > smp_rmb(); > > ret = wait_event_interruptible(q->mq_freeze_wq, > - !atomic_read(&q->mq_freeze_depth) || > + (atomic_read(&q->mq_freeze_depth) == 0 && > + (preempt || !blk_queue_preempt_only(q))) || > blk_queue_dying(q)); > if (blk_queue_dying(q)) > return -ENODEV; > @@ -1442,8 +1469,7 @@ static struct request *blk_old_get_request(struct request_queue *q, > /* create ioc upfront */ > create_io_context(gfp_mask, q->node); > > - ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM) || > - (op & REQ_NOWAIT)); > + ret = blk_queue_enter(q, flags); > if (ret) > return ERR_PTR(ret); > spin_lock_irq(q->queue_lock); > @@ -2264,8 +2290,10 @@ blk_qc_t generic_make_request(struct bio *bio) > current->bio_list = bio_list_on_stack; > do { > struct request_queue *q = bio->bi_disk->queue; > + unsigned int flags = bio->bi_opf & REQ_NOWAIT ? > + BLK_MQ_REQ_NOWAIT : 0; > > - if (likely(blk_queue_enter(q, bio->bi_opf & REQ_NOWAIT) == 0)) { > + if (likely(blk_queue_enter(q, flags) == 0)) { > struct bio_list lower, same; > > /* Create a fresh bio_list for all subordinate requests */ > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 6a025b17caac..c6bff60e6b8b 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -386,7 +386,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, > struct request *rq; > int ret; > > - ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT); > + ret = blk_queue_enter(q, flags); > if (ret) > return ERR_PTR(ret); > > @@ -425,7 +425,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, > if (hctx_idx >= q->nr_hw_queues) > return ERR_PTR(-EIO); > > - ret = blk_queue_enter(q, true); > + ret = blk_queue_enter(q, flags); > if (ret) > return ERR_PTR(ret); > > diff --git a/block/blk-timeout.c b/block/blk-timeout.c > index e3e9c9771d36..1eba71486716 100644 > --- a/block/blk-timeout.c > +++ b/block/blk-timeout.c > @@ -134,7 +134,7 @@ void blk_timeout_work(struct work_struct *work) > struct request *rq, *tmp; > int next_set = 0; > > - if (blk_queue_enter(q, true)) > + if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT)) > return; > spin_lock_irqsave(q->queue_lock, flags); > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 7c119696402c..2939f3a74fdc 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -2955,21 +2955,37 @@ static void scsi_wait_for_queuecommand(struct scsi_device *sdev) > int > scsi_device_quiesce(struct scsi_device *sdev) > { > + struct request_queue *q = sdev->request_queue; > int err; > > + /* > + * It is allowed to call scsi_device_quiesce() multiple times from > + * the same context but concurrent scsi_device_quiesce() calls are > + * not allowed. > + */ > + WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current); If the above line and comment is removed, everything is still fine, either nested calling or concurrent calling, isn't it? > + > + blk_set_preempt_only(q); > + > + blk_mq_freeze_queue(q); > + /* > + * Ensure that the effect of blk_set_preempt_only() will be visible > + * for percpu_ref_tryget() callers that occur after the queue > + * unfreeze even if the queue was already frozen before this function > + * was called. See also https://lwn.net/Articles/573497/. > + */ > + synchronize_rcu(); > + blk_mq_unfreeze_queue(q); > + > mutex_lock(&sdev->state_mutex); > err = scsi_device_set_state(sdev, SDEV_QUIESCE); > + if (err == 0) > + sdev->quiesced_by = current; > + else > + blk_clear_preempt_only(q); > mutex_unlock(&sdev->state_mutex); > > - if (err) > - return err; > - > - scsi_run_queue(sdev->request_queue); > - while (atomic_read(&sdev->device_busy)) { > - msleep_interruptible(200); > - scsi_run_queue(sdev->request_queue); > - } > - return 0; > + return err; > } > EXPORT_SYMBOL(scsi_device_quiesce); > > @@ -2990,8 +3006,10 @@ void scsi_device_resume(struct scsi_device *sdev) > */ > mutex_lock(&sdev->state_mutex); > if (sdev->sdev_state == SDEV_QUIESCE && > - scsi_device_set_state(sdev, SDEV_RUNNING) == 0) > - scsi_run_queue(sdev->request_queue); > + scsi_device_set_state(sdev, SDEV_RUNNING) == 0) { > + blk_clear_preempt_only(sdev->request_queue); > + sdev->quiesced_by = NULL; > + } > mutex_unlock(&sdev->state_mutex); > } > EXPORT_SYMBOL(scsi_device_resume); > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 07ddccd17801..c5363186618b 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -662,7 +662,7 @@ int bdev_read_page(struct block_device *bdev, sector_t sector, > if (!ops->rw_page || bdev_get_integrity(bdev)) > return result; > > - result = blk_queue_enter(bdev->bd_queue, false); > + result = blk_queue_enter(bdev->bd_queue, 0); > if (result) > return result; > result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, false); > @@ -698,7 +698,7 @@ int bdev_write_page(struct block_device *bdev, sector_t sector, > > if (!ops->rw_page || bdev_get_integrity(bdev)) > return -EOPNOTSUPP; > - result = blk_queue_enter(bdev->bd_queue, false); > + result = blk_queue_enter(bdev->bd_queue, 0); > if (result) > return result; > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 864ad2e4a58c..4f91c6462752 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -956,7 +956,7 @@ extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t, > extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t, > struct scsi_ioctl_command __user *); > > -extern int blk_queue_enter(struct request_queue *q, bool nowait); > +extern int blk_queue_enter(struct request_queue *q, unsigned int flags); > extern void blk_queue_exit(struct request_queue *q); > extern void blk_start_queue(struct request_queue *q); > extern void blk_start_queue_async(struct request_queue *q); > diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h > index 82e93ee94708..6f0f1e242e23 100644 > --- a/include/scsi/scsi_device.h > +++ b/include/scsi/scsi_device.h > @@ -219,6 +219,7 @@ struct scsi_device { > unsigned char access_state; > struct mutex state_mutex; > enum scsi_device_state sdev_state; > + struct task_struct *quiesced_by; > unsigned long sdev_data[0]; > } __attribute__((aligned(sizeof(unsigned long)))); > > -- > 2.14.2 >
Bart, > The contexts from which a SCSI device can be quiesced or resumed are: > * Writing into /sys/class/scsi_device/*/device/state. > * SCSI parallel (SPI) domain validation. > * The SCSI device power management methods. See also scsi_bus_pm_ops. The SCSI bits look fine to me. Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
On 10/17/2017 01:29 AM, Bart Van Assche wrote: > The contexts from which a SCSI device can be quiesced or resumed are: > * Writing into /sys/class/scsi_device/*/device/state. > * SCSI parallel (SPI) domain validation. > * The SCSI device power management methods. See also scsi_bus_pm_ops. > > It is essential during suspend and resume that neither the filesystem > state nor the filesystem metadata in RAM changes. This is why while > the hibernation image is being written or restored that SCSI devices > are quiesced. The SCSI core quiesces devices through scsi_device_quiesce() > and scsi_device_resume(). In the SDEV_QUIESCE state execution of > non-preempt requests is deferred. This is realized by returning > BLKPREP_DEFER from inside scsi_prep_state_check() for quiesced SCSI > devices. Avoid that a full queue prevents power management requests > to be submitted by deferring allocation of non-preempt requests for > devices in the quiesced state. This patch has been tested by running > the following commands and by verifying that after resume the fio job > is still running: > (We've discussed this at ALPSS already:) How do you ensure that PREEMPT requests are not stuck in the queue _behind_ non-PREEMPT requests? Once they are in the queue the request are already allocated, so your deferred allocation won't work. _And_ deferred requests will be re-inserted at the head of the queue. Consequently the PREEMPT request will never ever scheduled during quiesce. How do you avoid such a scenario? Cheers, Hannes
On Tue, Oct 17, 2017 at 08:33:36AM +0200, Hannes Reinecke wrote: > On 10/17/2017 01:29 AM, Bart Van Assche wrote: > > The contexts from which a SCSI device can be quiesced or resumed are: > > * Writing into /sys/class/scsi_device/*/device/state. > > * SCSI parallel (SPI) domain validation. > > * The SCSI device power management methods. See also scsi_bus_pm_ops. > > > > It is essential during suspend and resume that neither the filesystem > > state nor the filesystem metadata in RAM changes. This is why while > > the hibernation image is being written or restored that SCSI devices > > are quiesced. The SCSI core quiesces devices through scsi_device_quiesce() > > and scsi_device_resume(). In the SDEV_QUIESCE state execution of > > non-preempt requests is deferred. This is realized by returning > > BLKPREP_DEFER from inside scsi_prep_state_check() for quiesced SCSI > > devices. Avoid that a full queue prevents power management requests > > to be submitted by deferring allocation of non-preempt requests for > > devices in the quiesced state. This patch has been tested by running > > the following commands and by verifying that after resume the fio job > > is still running: > > > (We've discussed this at ALPSS already:) > > How do you ensure that PREEMPT requests are not stuck in the queue > _behind_ non-PREEMPT requests? Once the PREEMP_ONLY flag is set, blk_mq_freeze_queue() is called for draining up all requests in queue first, and new requests are prevented from being allocated meantime. So looks no such issue? > Once they are in the queue the request are already allocated, so your > deferred allocation won't work. > _And_ deferred requests will be re-inserted at the head of the queue. > Consequently the PREEMPT request will never ever scheduled during quiesce. > How do you avoid such a scenario? From the implementation, no any PREEMPT request can be allocated once scsi_device_quiesce() returns. Also not see deferred requests in this patch, could you explain it a bit?
On Tue, 2017-10-17 at 08:43 +0800, Ming Lei wrote: > On Mon, Oct 16, 2017 at 04:29:04PM -0700, Bart Van Assche wrote: > > [ ... ] > > int > > scsi_device_quiesce(struct scsi_device *sdev) > > { > > + struct request_queue *q = sdev->request_queue; > > int err; > > > > + /* > > + * It is allowed to call scsi_device_quiesce() multiple times from > > + * the same context but concurrent scsi_device_quiesce() calls are > > + * not allowed. > > + */ > > + WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current); > > If the above line and comment is removed, everything is still fine, > either nested calling or concurrent calling, isn't it? If scsi_device_quiesce() is called concurrently from two different threads then the first scsi_device_resume() call will resume I/O for *both* contexts. That's not what the callers expect. If scsi_device_quiesce() and scsi_device_resume() are called concurrently that would be even worse. I think we *really* should know whether callers serialize scsi_device_quiesce() and scsi_device_resume() calls properly. Hence the WARN_ON_ONCE() statement. Bart.
On Tue, 2017-10-17 at 08:33 +0200, Hannes Reinecke wrote: > How do you ensure that PREEMPT requests are not stuck in the queue > _behind_ non-PREEMPT requests? > Once they are in the queue the request are already allocated, so your > deferred allocation won't work. > _And_ deferred requests will be re-inserted at the head of the queue. > Consequently the PREEMPT request will never ever scheduled during quiesce. > How do you avoid such a scenario? Hello Hannes, The blk_mq_freeze_queue() / blk_mq_unfreeze_queue() calls that have been added through patch 9/10 to scsi_device_quiesce() will only succeed after all outstanding requests have finished. That includes non-preempt requests and requests that are about to be requeued. The changes in scsi_device_quiesce() are such that blk_queue_enter() will fail for non-preempt requests after the queue has been unfrozen. In other words, if a scsi_device_quiesce() call succeeds, it is guaranteed that there are no non-preempt requests in the queue and also that no new non-preempt requests will enter the queue until scsi_device_resume() is called. Bart.
On 10/17/2017 10:18 PM, Bart Van Assche wrote: > On Tue, 2017-10-17 at 08:33 +0200, Hannes Reinecke wrote: >> How do you ensure that PREEMPT requests are not stuck in the queue >> _behind_ non-PREEMPT requests? >> Once they are in the queue the request are already allocated, so your >> deferred allocation won't work. >> _And_ deferred requests will be re-inserted at the head of the queue. >> Consequently the PREEMPT request will never ever scheduled during quiesce. >> How do you avoid such a scenario? > > Hello Hannes, > > The blk_mq_freeze_queue() / blk_mq_unfreeze_queue() calls that have been > added through patch 9/10 to scsi_device_quiesce() will only succeed after all > outstanding requests have finished. That includes non-preempt requests and > requests that are about to be requeued. The changes in scsi_device_quiesce() > are such that blk_queue_enter() will fail for non-preempt requests after the > queue has been unfrozen. In other words, if a scsi_device_quiesce() call > succeeds, it is guaranteed that there are no non-preempt requests in the queue > and also that no new non-preempt requests will enter the queue until > scsi_device_resume() is called. > Ah. Right. That was the explanation I was after. Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
diff --git a/block/blk-core.c b/block/blk-core.c index b73203286bf5..abb5095bcef6 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -372,6 +372,7 @@ void blk_clear_preempt_only(struct request_queue *q) spin_lock_irqsave(q->queue_lock, flags); queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q); + wake_up_all(&q->mq_freeze_wq); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL_GPL(blk_clear_preempt_only); @@ -793,15 +794,40 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask) } EXPORT_SYMBOL(blk_alloc_queue); -int blk_queue_enter(struct request_queue *q, bool nowait) +/** + * blk_queue_enter() - try to increase q->q_usage_counter + * @q: request queue pointer + * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PREEMPT + */ +int blk_queue_enter(struct request_queue *q, unsigned int flags) { + const bool preempt = flags & BLK_MQ_REQ_PREEMPT; + while (true) { + bool success = false; int ret; - if (percpu_ref_tryget_live(&q->q_usage_counter)) + rcu_read_lock_sched(); + if (percpu_ref_tryget_live(&q->q_usage_counter)) { + /* + * The code that sets the PREEMPT_ONLY flag is + * responsible for ensuring that that flag is globally + * visible before the queue is unfrozen. + */ + if (preempt || !blk_queue_preempt_only(q)) { + success = true; + } else { + percpu_ref_put(&q->q_usage_counter); + WARN_ONCE("%s: Attempt to allocate non-preempt request in preempt-only mode.\n", + kobject_name(q->kobj.parent)); + } + } + rcu_read_unlock_sched(); + + if (success) return 0; - if (nowait) + if (flags & BLK_MQ_REQ_NOWAIT) return -EBUSY; /* @@ -814,7 +840,8 @@ int blk_queue_enter(struct request_queue *q, bool nowait) smp_rmb(); ret = wait_event_interruptible(q->mq_freeze_wq, - !atomic_read(&q->mq_freeze_depth) || + (atomic_read(&q->mq_freeze_depth) == 0 && + (preempt || !blk_queue_preempt_only(q))) || blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; @@ -1442,8 +1469,7 @@ static struct request *blk_old_get_request(struct request_queue *q, /* create ioc upfront */ create_io_context(gfp_mask, q->node); - ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM) || - (op & REQ_NOWAIT)); + ret = blk_queue_enter(q, flags); if (ret) return ERR_PTR(ret); spin_lock_irq(q->queue_lock); @@ -2264,8 +2290,10 @@ blk_qc_t generic_make_request(struct bio *bio) current->bio_list = bio_list_on_stack; do { struct request_queue *q = bio->bi_disk->queue; + unsigned int flags = bio->bi_opf & REQ_NOWAIT ? + BLK_MQ_REQ_NOWAIT : 0; - if (likely(blk_queue_enter(q, bio->bi_opf & REQ_NOWAIT) == 0)) { + if (likely(blk_queue_enter(q, flags) == 0)) { struct bio_list lower, same; /* Create a fresh bio_list for all subordinate requests */ diff --git a/block/blk-mq.c b/block/blk-mq.c index 6a025b17caac..c6bff60e6b8b 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -386,7 +386,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, struct request *rq; int ret; - ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT); + ret = blk_queue_enter(q, flags); if (ret) return ERR_PTR(ret); @@ -425,7 +425,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, if (hctx_idx >= q->nr_hw_queues) return ERR_PTR(-EIO); - ret = blk_queue_enter(q, true); + ret = blk_queue_enter(q, flags); if (ret) return ERR_PTR(ret); diff --git a/block/blk-timeout.c b/block/blk-timeout.c index e3e9c9771d36..1eba71486716 100644 --- a/block/blk-timeout.c +++ b/block/blk-timeout.c @@ -134,7 +134,7 @@ void blk_timeout_work(struct work_struct *work) struct request *rq, *tmp; int next_set = 0; - if (blk_queue_enter(q, true)) + if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT)) return; spin_lock_irqsave(q->queue_lock, flags); diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 7c119696402c..2939f3a74fdc 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2955,21 +2955,37 @@ static void scsi_wait_for_queuecommand(struct scsi_device *sdev) int scsi_device_quiesce(struct scsi_device *sdev) { + struct request_queue *q = sdev->request_queue; int err; + /* + * It is allowed to call scsi_device_quiesce() multiple times from + * the same context but concurrent scsi_device_quiesce() calls are + * not allowed. + */ + WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current); + + blk_set_preempt_only(q); + + blk_mq_freeze_queue(q); + /* + * Ensure that the effect of blk_set_preempt_only() will be visible + * for percpu_ref_tryget() callers that occur after the queue + * unfreeze even if the queue was already frozen before this function + * was called. See also https://lwn.net/Articles/573497/. + */ + synchronize_rcu(); + blk_mq_unfreeze_queue(q); + mutex_lock(&sdev->state_mutex); err = scsi_device_set_state(sdev, SDEV_QUIESCE); + if (err == 0) + sdev->quiesced_by = current; + else + blk_clear_preempt_only(q); mutex_unlock(&sdev->state_mutex); - if (err) - return err; - - scsi_run_queue(sdev->request_queue); - while (atomic_read(&sdev->device_busy)) { - msleep_interruptible(200); - scsi_run_queue(sdev->request_queue); - } - return 0; + return err; } EXPORT_SYMBOL(scsi_device_quiesce); @@ -2990,8 +3006,10 @@ void scsi_device_resume(struct scsi_device *sdev) */ mutex_lock(&sdev->state_mutex); if (sdev->sdev_state == SDEV_QUIESCE && - scsi_device_set_state(sdev, SDEV_RUNNING) == 0) - scsi_run_queue(sdev->request_queue); + scsi_device_set_state(sdev, SDEV_RUNNING) == 0) { + blk_clear_preempt_only(sdev->request_queue); + sdev->quiesced_by = NULL; + } mutex_unlock(&sdev->state_mutex); } EXPORT_SYMBOL(scsi_device_resume); diff --git a/fs/block_dev.c b/fs/block_dev.c index 07ddccd17801..c5363186618b 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -662,7 +662,7 @@ int bdev_read_page(struct block_device *bdev, sector_t sector, if (!ops->rw_page || bdev_get_integrity(bdev)) return result; - result = blk_queue_enter(bdev->bd_queue, false); + result = blk_queue_enter(bdev->bd_queue, 0); if (result) return result; result = ops->rw_page(bdev, sector + get_start_sect(bdev), page, false); @@ -698,7 +698,7 @@ int bdev_write_page(struct block_device *bdev, sector_t sector, if (!ops->rw_page || bdev_get_integrity(bdev)) return -EOPNOTSUPP; - result = blk_queue_enter(bdev->bd_queue, false); + result = blk_queue_enter(bdev->bd_queue, 0); if (result) return result; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 864ad2e4a58c..4f91c6462752 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -956,7 +956,7 @@ extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t, extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t, struct scsi_ioctl_command __user *); -extern int blk_queue_enter(struct request_queue *q, bool nowait); +extern int blk_queue_enter(struct request_queue *q, unsigned int flags); extern void blk_queue_exit(struct request_queue *q); extern void blk_start_queue(struct request_queue *q); extern void blk_start_queue_async(struct request_queue *q); diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 82e93ee94708..6f0f1e242e23 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -219,6 +219,7 @@ struct scsi_device { unsigned char access_state; struct mutex state_mutex; enum scsi_device_state sdev_state; + struct task_struct *quiesced_by; unsigned long sdev_data[0]; } __attribute__((aligned(sizeof(unsigned long))));
The contexts from which a SCSI device can be quiesced or resumed are: * Writing into /sys/class/scsi_device/*/device/state. * SCSI parallel (SPI) domain validation. * The SCSI device power management methods. See also scsi_bus_pm_ops. It is essential during suspend and resume that neither the filesystem state nor the filesystem metadata in RAM changes. This is why while the hibernation image is being written or restored that SCSI devices are quiesced. The SCSI core quiesces devices through scsi_device_quiesce() and scsi_device_resume(). In the SDEV_QUIESCE state execution of non-preempt requests is deferred. This is realized by returning BLKPREP_DEFER from inside scsi_prep_state_check() for quiesced SCSI devices. Avoid that a full queue prevents power management requests to be submitted by deferring allocation of non-preempt requests for devices in the quiesced state. This patch has been tested by running the following commands and by verifying that after resume the fio job is still running: for d in /sys/class/block/sd*[a-z]; do hcil=$(readlink "$d/device") hcil=${hcil#../../../} echo 4 > "$d/queue/nr_requests" echo 1 > "/sys/class/scsi_device/$hcil/device/queue_depth" done bdev=$(readlink /dev/disk/by-uuid/5217d83f-213e-4b42-b86e-20013325ba6c) bdev=${bdev#../../} hcil=$(readlink "/sys/block/$bdev/device") hcil=${hcil#../../../} fio --name="$bdev" --filename="/dev/$bdev" --buffered=0 --bs=512 --rw=randread \ --ioengine=libaio --numjobs=4 --iodepth=16 --iodepth_batch=1 --thread \ --loops=$((2**31)) & pid=$! sleep 1 systemctl hibernate sleep 10 kill $pid Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name> References: "I/O hangs after resuming from suspend-to-ram" (https://marc.info/?l=linux-block&m=150340235201348). Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Tested-by: Martin Steigerwald <martin@lichtvoll.de> Cc: Martin K. Petersen <martin.petersen@oracle.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> --- block/blk-core.c | 42 +++++++++++++++++++++++++++++++++++------- block/blk-mq.c | 4 ++-- block/blk-timeout.c | 2 +- drivers/scsi/scsi_lib.c | 40 +++++++++++++++++++++++++++++----------- fs/block_dev.c | 4 ++-- include/linux/blkdev.h | 2 +- include/scsi/scsi_device.h | 1 + 7 files changed, 71 insertions(+), 24 deletions(-)