Re: [PATCH 3/4] block: move queue enter logic into blk_mq_submit_bio()

[Jens Axboe <axboe@xxxxxxxxx>]

On 11/4/21 5:41 AM, Jens Axboe wrote:
>> This is broken, we really ant the submit checks under freeze
>> protection to make sure the parameters can't be changed underneath
>> us.
> 
> Which parameters are you worried about in submit_bio_checks()? I don't
> immediately see anything that would make me worry about it.

To player it safer, I would suggest we fold in something like the
below. That keeps the submit_checks() under the queue enter.


diff --git a/block/blk-core.c b/block/blk-core.c
index 2b12a427ffa6..18aab7f8469a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -746,7 +746,7 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
 	return BLK_STS_OK;
 }
 
-static noinline_for_stack bool submit_bio_checks(struct bio *bio)
+noinline_for_stack bool submit_bio_checks(struct bio *bio)
 {
 	struct block_device *bdev = bio->bi_bdev;
 	struct request_queue *q = bdev_get_queue(bdev);
@@ -868,14 +868,13 @@ static void __submit_bio(struct bio *bio)
 {
 	struct gendisk *disk = bio->bi_bdev->bd_disk;
 
-	if (!submit_bio_checks(bio) || !blk_crypto_bio_prep(&bio))
-		return;
 	if (!disk->fops->submit_bio) {
 		blk_mq_submit_bio(bio);
 	} else {
 		if (unlikely(bio_queue_enter(bio) != 0))
 			return;
-		disk->fops->submit_bio(bio);
+		if (submit_bio_checks(bio) && blk_crypto_bio_prep(&bio))
+			disk->fops->submit_bio(bio);
 		blk_queue_exit(disk->queue);
 	}
 }
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e92c36f2326a..2dab9bdcc51a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2526,6 +2526,9 @@ void blk_mq_submit_bio(struct bio *bio)
 	unsigned int nr_segs = 1;
 	blk_status_t ret;
 
+	if (unlikely(!blk_crypto_bio_prep(&bio)))
+		return;
+
 	blk_queue_bounce(q, &bio);
 	if (blk_may_split(q, bio))
 		__blk_queue_split(q, &bio, &nr_segs);
@@ -2551,6 +2554,8 @@ void blk_mq_submit_bio(struct bio *bio)
 
 		if (unlikely(!blk_mq_queue_enter(q, bio)))
 			return;
+		if (unlikely(!submit_bio_checks(bio)))
+			goto put_exit;
 
 		rq_qos_throttle(q, bio);
 
diff --git a/block/blk.h b/block/blk.h
index f7371d3b1522..79c98ced59c8 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -56,6 +56,7 @@ void blk_freeze_queue(struct request_queue *q);
 void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic);
 void blk_queue_start_drain(struct request_queue *q);
 int bio_queue_enter(struct bio *bio);
+bool submit_bio_checks(struct bio *bio);
 
 static inline bool blk_try_enter_queue(struct request_queue *q, bool pm)
 {

-- 
Jens Axboe