Implement the following approach for blk-mq: - Either make blk_get_request() wait or make it fail when a request queue is not in status RPM_ACTIVE. - While suspending, suspended or resuming, only process power management requests (REQ_PM).
Reported-by: Oleksandr Natalenko <[email protected]> References: "I/O hangs after resuming from suspend-to-ram" (https://marc.info/?l=linux-block&m=150340235201348). Signed-off-by: Bart Van Assche <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Hannes Reinecke <[email protected]> Cc: Johannes Thumshirn <[email protected]> Cc: Rafael J. Wysocki <[email protected]> Cc: Ming Lei <[email protected]> --- block/blk-core.c | 20 ++++++++++++++++---- block/blk-mq.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 4 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index cd2700c763ed..49a4cd5b255e 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -3438,10 +3438,6 @@ EXPORT_SYMBOL(blk_finish_plug); */ void blk_pm_runtime_init(struct request_queue *q, struct device *dev) { - /* not support for RQF_PM and ->rpm_status in blk-mq yet */ - if (q->mq_ops) - return; - q->dev = dev; q->rpm_status = RPM_ACTIVE; init_waitqueue_head(&q->rpm_active_wq); @@ -3478,6 +3474,19 @@ int blk_pre_runtime_suspend(struct request_queue *q) if (!q->dev) return ret; + if (q->mq_ops) { + percpu_ref_switch_to_atomic_nowait(&q->q_usage_counter); + if (!percpu_ref_is_zero(&q->q_usage_counter)) { + ret = -EBUSY; + pm_runtime_mark_last_busy(q->dev); + } else { + spin_lock_irq(q->queue_lock); + q->rpm_status = RPM_SUSPENDING; + spin_unlock_irq(q->queue_lock); + } + return ret; + } + spin_lock_irq(q->queue_lock); if (q->nr_pending) { ret = -EBUSY; @@ -3561,6 +3570,9 @@ void blk_post_runtime_resume(struct request_queue *q, int err) if (!q->dev) return; + if (q->mq_ops) + percpu_ref_switch_to_percpu(&q->q_usage_counter); + spin_lock_irq(q->queue_lock); if (!err) { q->rpm_status = RPM_ACTIVE; diff --git a/block/blk-mq.c b/block/blk-mq.c index 3f18cff80050..cbd680dc194a 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -383,6 +383,29 @@ static struct request *blk_mq_get_request(struct request_queue *q, return rq; } +#ifdef CONFIG_PM +static bool blk_mq_wait_until_active(struct request_queue *q, bool wait) +{ + if (!wait) + return false; + /* + * Note: the q->rpm_status check below races against the changes of + * that variable by the blk_{pre,post}_runtime_{suspend,resume}() + * functions. The worst possible consequence of these races is that a + * small number of requests gets passed to the block driver associated + * with the request queue after rpm_status has been changed into + * RPM_SUSPENDING and before it is changed into RPM_SUSPENDED. + */ + wait_event(q->rpm_active_wq, q->rpm_status == RPM_ACTIVE); + return true; +} +#else +static bool blk_mq_wait_until_active(struct request_queue *q, bool nowait) +{ + return true; +} +#endif + struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, unsigned int flags) { @@ -390,6 +413,17 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, struct request *rq; int ret; + WARN_ON_ONCE((op & REQ_PM) && blk_pm_suspended(q)); + + /* + * Wait if the request queue is suspended or in the process of + * suspending/resuming and the request being allocated will not be + * used for power management purposes. + */ + if (!(op & REQ_PM) && + !blk_mq_wait_until_active(q, !(op & REQ_NOWAIT))) + return ERR_PTR(-EAGAIN); + ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT); if (ret) return ERR_PTR(ret); -- 2.14.1
