One of the optimizations in the block layer is that the software queues
are bypassed if it is expected that the block driver will accept a
request. This can cause request reordering even for requests submitted
from the same CPU core. This patch preserves the order for sequential
zoned writes submitted from a given CPU core by always inserting these
requests into the appropriate software queue.
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/blk-mq.c | 27 +++++++++++++++++++++++++--
include/linux/blk-mq.h | 11 +++++++++++
2 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b1d81839679f..445f2275eddb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1537,6 +1537,27 @@ void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
}
EXPORT_SYMBOL(blk_mq_requeue_request);
+/*
+ * Whether the block layer should preserve the order of @rq relative to other
+ * requests submitted to the same software queue.
+ */
+static bool blk_mq_preserve_order(struct request *rq)
+{
+ return rq->q->limits.features & BLK_FEAT_ORDERED_HWQ &&
+ blk_rq_is_seq_zoned_write(rq);
+}
+
+static bool blk_mq_preserve_order_for_list(struct list_head *list)
+{
+ struct request *rq;
+
+ list_for_each_entry(rq, list, queuelist)
+ if (blk_mq_preserve_order(rq))
+ return true;
+
+ return false;
+}
+
static void blk_mq_requeue_work(struct work_struct *work)
{
struct request_queue *q =
@@ -2566,7 +2587,8 @@ static void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx,
* Try to issue requests directly if the hw queue isn't busy to save an
* extra enqueue & dequeue to the sw queue.
*/
- if (!hctx->dispatch_busy && !run_queue_async) {
+ if (!hctx->dispatch_busy && !run_queue_async &&
+ !blk_mq_preserve_order_for_list(list)) {
blk_mq_run_dispatch_ops(hctx->queue,
blk_mq_try_issue_list_directly(hctx, list));
if (list_empty(list))
@@ -3215,7 +3237,8 @@ void blk_mq_submit_bio(struct bio *bio)
hctx = rq->mq_hctx;
if ((rq->rq_flags & RQF_USE_SCHED) ||
- (hctx->dispatch_busy && (q->nr_hw_queues == 1 || !is_sync))) {
+ (hctx->dispatch_busy && (q->nr_hw_queues == 1 || !is_sync)) ||
+ blk_mq_preserve_order(rq)) {
blk_mq_insert_request(rq, 0);
blk_mq_run_hw_queue(hctx, true);
} else {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 2a5a828f19a0..30d7cd1b0484 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -1191,4 +1191,15 @@ static inline int blk_rq_map_sg(struct request *rq, struct scatterlist *sglist)
}
void blk_dump_rq_flags(struct request *, char *);
+static inline bool blk_rq_is_seq_zoned_write(struct request *rq)
+{
+ switch (req_op(rq)) {
+ case REQ_OP_WRITE:
+ case REQ_OP_WRITE_ZEROES:
+ return bdev_zone_is_seq(rq->q->disk->part0, blk_rq_pos(rq));
+ default:
+ return false;
+ }
+}
+
#endif /* BLK_MQ_H */
