Commit 49d24398 authored by Uday Shankar's avatar Uday Shankar Committed by Jens Axboe
Browse files

blk-mq: enforce op-specific segment limits in blk_insert_cloned_request 



The block layer might merge together discard requests up until the
max_discard_segments limit is hit, but blk_insert_cloned_request checks
the segment count against max_segments regardless of the req op. This
can result in errors like the following when discards are issued through
a DM device and max_discard_segments exceeds max_segments for the queue
of the chosen underlying device.

blk_insert_cloned_request: over max segments limit. (256 > 129)

Fix this by looking at the req_op and enforcing the appropriate segment
limit - max_discard_segments for REQ_OP_DISCARDs and max_segments for
everything else.

Signed-off-by: default avatarUday Shankar <ushankar@purestorage.com>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230301000655.48112-1-ushankar@purestorage.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 326ac2c5

block/blk-merge.c

+0 −7
Original line number Diff line number Diff line
@@ -586,13 +586,6 @@ int __blk_rq_map_sg(struct request_queue *q, struct request *rq, 
}

EXPORT_SYMBOL(__blk_rq_map_sg);



static inline unsigned int blk_rq_get_max_segments(struct request *rq)

{

	if (req_op(rq) == REQ_OP_DISCARD)

		return queue_max_discard_segments(rq->q);

	return queue_max_segments(rq->q);

}



static inline unsigned int blk_rq_get_max_sectors(struct request *rq,

						  sector_t offset)

{

block/blk-mq.c

+4 −3
Original line number Diff line number Diff line
@@ -3000,6 +3000,7 @@ blk_status_t blk_insert_cloned_request(struct request *rq) 
{

	struct request_queue *q = rq->q;

	unsigned int max_sectors = blk_queue_get_max_sectors(q, req_op(rq));

	unsigned int max_segments = blk_rq_get_max_segments(rq);

	blk_status_t ret;



	if (blk_rq_sectors(rq) > max_sectors) {
@@ -3026,9 +3027,9 @@ blk_status_t blk_insert_cloned_request(struct request *rq) 
	 * original queue.

	 */

	rq->nr_phys_segments = blk_recalc_rq_segments(rq);

	if (rq->nr_phys_segments > queue_max_segments(q)) {

		printk(KERN_ERR "%s: over max segments limit. (%hu > %hu)\n",

			__func__, rq->nr_phys_segments, queue_max_segments(q));

	if (rq->nr_phys_segments > max_segments) {

		printk(KERN_ERR "%s: over max segments limit. (%u > %u)\n",

			__func__, rq->nr_phys_segments, max_segments);

		return BLK_STS_IOERR;

	}

block/blk.h

+7 −0
Original line number Diff line number Diff line
@@ -156,6 +156,13 @@ static inline bool blk_discard_mergable(struct request *req) 
	return false;

}



static inline unsigned int blk_rq_get_max_segments(struct request *rq)

{

	if (req_op(rq) == REQ_OP_DISCARD)

		return queue_max_discard_segments(rq->q);

	return queue_max_segments(rq->q);

}



static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,

						     enum req_op op)

{