From c246e80d86736312933646896c4157daf511dadc Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 6 Dec 2012 14:32:01 +0100 Subject: block: Avoid that request_fn is invoked on a dead queue A block driver may start cleaning up resources needed by its request_fn as soon as blk_cleanup_queue() finished, so request_fn must not be invoked after draining finished. This is important when blk_run_queue() is invoked without any requests in progress. As an example, if blk_drain_queue() and scsi_run_queue() run in parallel, blk_drain_queue() may have finished all requests after scsi_run_queue() has taken a SCSI device off the starved list but before that last function has had a chance to run the queue. Signed-off-by: Bart Van Assche Cc: James Bottomley Cc: Mike Christie Cc: Chanho Min Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- block/blk-core.c | 31 +++++++++++++++++++++++++++---- block/blk-exec.c | 2 +- block/blk.h | 2 ++ include/linux/blkdev.h | 2 ++ 4 files changed, 32 insertions(+), 5 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index a182b586b06a..f52d05ff5d24 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -292,6 +292,25 @@ void blk_sync_queue(struct request_queue *q) } EXPORT_SYMBOL(blk_sync_queue); +/** + * __blk_run_queue_uncond - run a queue whether or not it has been stopped + * @q: The queue to run + * + * Description: + * Invoke request handling on a queue if there are any pending requests. + * May be used to restart request handling after a request has completed. + * This variant runs the queue whether or not the queue has been + * stopped. Must be called with the queue lock held and interrupts + * disabled. See also @blk_run_queue. + */ +inline void __blk_run_queue_uncond(struct request_queue *q) +{ + if (unlikely(blk_queue_dead(q))) + return; + + q->request_fn(q); +} + /** * __blk_run_queue - run a single device queue * @q: The queue to run @@ -305,7 +324,7 @@ void __blk_run_queue(struct request_queue *q) if (unlikely(blk_queue_stopped(q))) return; - q->request_fn(q); + __blk_run_queue_uncond(q); } EXPORT_SYMBOL(__blk_run_queue); @@ -477,8 +496,8 @@ EXPORT_SYMBOL_GPL(blk_queue_bypass_end); * blk_cleanup_queue - shutdown a request queue * @q: request queue to shutdown * - * Mark @q DYING, drain all pending requests, destroy and put it. All - * future requests will be failed immediately with -ENODEV. + * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and + * put it. All future requests will be failed immediately with -ENODEV. */ void blk_cleanup_queue(struct request_queue *q) { @@ -507,9 +526,13 @@ void blk_cleanup_queue(struct request_queue *q) spin_unlock_irq(lock); mutex_unlock(&q->sysfs_lock); - /* drain all requests queued before DYING marking */ + /* + * Drain all requests queued before DYING marking. Set DEAD flag to + * prevent that q->request_fn() gets invoked after draining finished. + */ spin_lock_irq(lock); __blk_drain_queue(q, true); + queue_flag_set(QUEUE_FLAG_DEAD, q); spin_unlock_irq(lock); /* @q won't process any more request, flush async actions */ diff --git a/block/blk-exec.c b/block/blk-exec.c index 4aec98df7ba5..1320e74d79b8 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -72,7 +72,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, __blk_run_queue(q); /* the queue is stopped so it won't be run */ if (rq->cmd_type == REQ_TYPE_PM_RESUME) - q->request_fn(q); + __blk_run_queue_uncond(q); spin_unlock_irq(q->queue_lock); } EXPORT_SYMBOL_GPL(blk_execute_rq_nowait); diff --git a/block/blk.h b/block/blk.h index 2218a8a78292..47fdfdd41520 100644 --- a/block/blk.h +++ b/block/blk.h @@ -145,6 +145,8 @@ int blk_try_merge(struct request *rq, struct bio *bio); void blk_queue_congestion_threshold(struct request_queue *q); +void __blk_run_queue_uncond(struct request_queue *q); + int blk_dev_init(void); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index aba8246afe72..8bc46c250ca4 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -452,6 +452,7 @@ struct request_queue { #define QUEUE_FLAG_ADD_RANDOM 16 /* Contributes to random pool */ #define QUEUE_FLAG_SECDISCARD 17 /* supports SECDISCARD */ #define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */ +#define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ @@ -522,6 +523,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q) #define blk_queue_tagged(q) test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags) #define blk_queue_stopped(q) test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags) #define blk_queue_dying(q) test_bit(QUEUE_FLAG_DYING, &(q)->queue_flags) +#define blk_queue_dead(q) test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags) #define blk_queue_bypass(q) test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags) #define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags) #define blk_queue_noxmerges(q) \ -- cgit v1.2.3