[PATCH v2 1/3] block: warn if sharing request queue across gendisks

[PATCH v2 1/3] block: warn if sharing request queue across gendisks

[Omar Sandoval]

From: Omar Sandoval <osandov@fb.com>

Now that the remaining drivers have been converted to one request queue
per gendisk, let's warn if a request queue gets registered more than
once. This will catch future drivers which might do it inadvertently or
any old drivers that I may have missed.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 block/blk-sysfs.c      | 7 +++++++
 include/linux/blkdev.h | 1 +
 2 files changed, 8 insertions(+)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 7f090dd15ca6..833fb7f9ce9d 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -871,6 +871,11 @@ int blk_register_queue(struct gendisk *disk)
 	if (WARN_ON(!q))
 		return -ENXIO;
 
+	WARN_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags),
+		  "%s is registering an already registered queue\n",
+		  kobject_name(&dev->kobj));
+	queue_flag_set_unlocked(QUEUE_FLAG_REGISTERED, q);
+
 	/*
 	 * SCSI probing may synchronously create and destroy a lot of
 	 * request_queues for non-existent devices.  Shutting down a fully
@@ -931,6 +936,8 @@ void blk_unregister_queue(struct gendisk *disk)
 	if (WARN_ON(!q))
 		return;
 
+	queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q);
+
 	if (q->mq_ops)
 		blk_mq_unregister_dev(disk_to_dev(disk), q);
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1a7dc42a8918..a2dc6b390d48 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -617,6 +617,7 @@ struct request_queue {
 #define QUEUE_FLAG_STATS       27	/* track rq completion times */
 #define QUEUE_FLAG_RESTART     28	/* queue needs restart at completion */
 #define QUEUE_FLAG_POLL_STATS  29	/* collecting stats for hybrid polling */
+#define QUEUE_FLAG_REGISTERED  30	/* queue has been registered to a disk */
 
 #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_STACKABLE)	|	\
-- 
2.12.1

[PATCH v2 2/3] blk-mq: fix leak of q->stats

[Omar Sandoval]

From: Omar Sandoval <osandov@fb.com>

blk_alloc_queue_node() already allocates q->stats, so
blk_mq_init_allocated_queue() is overwriting it with a new allocation.

Fixes: a83b576c9c25 ("block: fix stacked driver stats init and free")
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 block/blk-mq.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7df9dbfab022..00eeef31db30 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2212,10 +2212,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	/* mark the queue as mq asap */
 	q->mq_ops = set->ops;
 
-	q->stats = blk_alloc_queue_stats();
-	if (!q->stats)
-		goto err_exit;
-
 	q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
 					     blk_stat_rq_ddir, 2, q);
 	if (!q->poll_cb)
-- 
2.12.1

[PATCH v2 3/3] block: fix leak of q->rq_wb

[Omar Sandoval]

From: Omar Sandoval <osandov@fb.com>

CONFIG_DEBUG_TEST_DRIVER_REMOVE found a possible leak of q->rq_wb when a
request queue is reregistered. This has been a problem since wbt was
introduced, but the WARN_ON(!list_empty(&stats->callbacks)) in the
blk-stat rework exposed it. Fix it by cleaning up wbt when we unregister
the queue.

Fixes: 87760e5eef35 ("block: hook up writeback throttling")
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 block/blk-sysfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 833fb7f9ce9d..45854266e398 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -795,7 +795,6 @@ static void blk_release_queue(struct kobject *kobj)
 	struct request_queue *q =
 		container_of(kobj, struct request_queue, kobj);
 
-	wbt_exit(q);
 	if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
 		blk_stat_remove_callback(q, q->poll_cb);
 	blk_stat_free_callback(q->poll_cb);
@@ -938,6 +937,9 @@ void blk_unregister_queue(struct gendisk *disk)
 
 	queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q);
 
+	wbt_exit(q);
+
+
 	if (q->mq_ops)
 		blk_mq_unregister_dev(disk_to_dev(disk), q);
 
-- 
2.12.1

Re: [PATCH v2 1/3] block: warn if sharing request queue across gendisks

[Jens Axboe]

On Tue, Mar 28 2017, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Now that the remaining drivers have been converted to one request queue
> per gendisk, let's warn if a request queue gets registered more than
> once. This will catch future drivers which might do it inadvertently or
> any old drivers that I may have missed.

Added 1-3 for 4.12, thanks. Final nail in the coffin for shared queues.

BTW, can you include a cover letter when it's more than one patch? Makes
the flow a bit more straight forward.

-- 
Jens Axboe

Re: [PATCH v2 1/3] block: warn if sharing request queue across gendisks

[Omar Sandoval]

On Wed, Mar 29, 2017 at 08:10:35AM -0600, Jens Axboe wrote:
> On Tue, Mar 28 2017, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > Now that the remaining drivers have been converted to one request queue
> > per gendisk, let's warn if a request queue gets registered more than
> > once. This will catch future drivers which might do it inadvertently or
> > any old drivers that I may have missed.
> 
> Added 1-3 for 4.12, thanks. Final nail in the coffin for shared queues.

Thanks!

> BTW, can you include a cover letter when it's more than one patch? Makes
> the flow a bit more straight forward.

Yeah, I'll make sure to do that in the future.