Commit 85067747 authored by Ming Lei's avatar Ming Lei Committed by Mike Snitzer
Browse files

dm: do not use waitqueue for request-based DM 



Given request-based DM now uses blk-mq's blk_mq_queue_inflight() to
determine if outstanding IO has completed (and DM has no control over
the blk-mq state machine used to track outstanding IO) it is unsafe to
wakeup waiter (dm_wait_for_completion) before blk-mq has cleared a
request's state bits (e.g. MQ_RQ_IN_FLIGHT or MQ_RQ_COMPLETE).  As
such dm_wait_for_completion() could be left to wait indefinitely if no
other requests complete.

Fix this by eliminating request-based DM's use of waitqueue to wait
for blk-mq requests to complete in dm_wait_for_completion.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Depends-on: 3c94d83c ("blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent dcb7fd82

drivers/md/dm-rq.c

+0 −4
Original line number Diff line number Diff line
@@ -146,10 +146,6 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig) 
 */

static void rq_completed(struct mapped_device *md)

{

	/* nudge anyone waiting on suspend queue */

	if (unlikely(wq_has_sleeper(&md->wait)))

		wake_up(&md->wait);



	/*

	 * dm_put() must be at the end of this function. See the comment above

	 */

drivers/md/dm.c

+39 −25
Original line number Diff line number Diff line
@@ -654,28 +654,6 @@ static void free_tio(struct dm_target_io *tio) 
	bio_put(&tio->clone);

}



static bool md_in_flight_bios(struct mapped_device *md)

{

	int cpu;

	struct hd_struct *part = &dm_disk(md)->part0;

	long sum = 0;



	for_each_possible_cpu(cpu) {

		sum += part_stat_local_read_cpu(part, in_flight[0], cpu);

		sum += part_stat_local_read_cpu(part, in_flight[1], cpu);

	}



	return sum != 0;

}



static bool md_in_flight(struct mapped_device *md)

{

	if (queue_is_mq(md->queue))

		return blk_mq_queue_inflight(md->queue);

	else

		return md_in_flight_bios(md);

}



u64 dm_start_time_ns_from_clone(struct bio *bio)

{

	struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);
@@ -2470,15 +2448,29 @@ void dm_put(struct mapped_device *md) 
}

EXPORT_SYMBOL_GPL(dm_put);



static int dm_wait_for_completion(struct mapped_device *md, long task_state)

static bool md_in_flight_bios(struct mapped_device *md)

{

	int cpu;

	struct hd_struct *part = &dm_disk(md)->part0;

	long sum = 0;



	for_each_possible_cpu(cpu) {

		sum += part_stat_local_read_cpu(part, in_flight[0], cpu);

		sum += part_stat_local_read_cpu(part, in_flight[1], cpu);

	}



	return sum != 0;

}



static int dm_wait_for_bios_completion(struct mapped_device *md, long task_state)

{

	int r = 0;

	DEFINE_WAIT(wait);



	while (1) {

	while (true) {

		prepare_to_wait(&md->wait, &wait, task_state);



		if (!md_in_flight(md))

		if (!md_in_flight_bios(md))

			break;



		if (signal_pending_state(task_state, current)) {
@@ -2493,6 +2485,28 @@ static int dm_wait_for_completion(struct mapped_device *md, long task_state) 
	return r;

}



static int dm_wait_for_completion(struct mapped_device *md, long task_state)

{

	int r = 0;



	if (!queue_is_mq(md->queue))

		return dm_wait_for_bios_completion(md, task_state);



	while (true) {

		if (!blk_mq_queue_inflight(md->queue))

			break;



		if (signal_pending_state(task_state, current)) {

			r = -EINTR;

			break;

		}



		msleep(5);

	}



	return r;

}



/*

 * Process the deferred bios

 */

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