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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 <bvanassche@acm.org>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Chanho Min <chanho.min@lge.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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bvanassche authored and axboe committed Dec 6, 2012
1 parent 807592a commit c246e80d86736312933646896c4157daf511dadc
Showing with 32 additions and 5 deletions.
  1. +27 −4 block/blk-core.c
  2. +1 −1 block/blk-exec.c
  3. +2 −0 block/blk.h
  4. +2 −0 include/linux/blkdev.h
View
@@ -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 */
View
@@ -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);
View
@@ -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);
View
@@ -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) \

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