[PATCH] block: check bio alignment in blk_mq_submit_bio

[Ming Lei <ming.lei@redhat.com>]

IO logical block size is one fundamental queue limit, and every IO has
to be aligned with logical block size because our bio split can't deal
with unaligned bio.

The check has to be done with queue usage counter grabbed because device
reconfiguration may change logical block size, and we can prevent the
reconfiguration from happening by holding queue usage counter.

logical_block_size stays in the 1st cache line of queue_limits, and this
cache line is always fetched in fast path via bio_may_exceed_limits(),
so IO perf won't be affected by this check.

Cc: Yi Zhang <yi.zhang@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ye Bin <yebin10@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3b4df8e5ac9e..7bb50b6b9567 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2914,6 +2914,21 @@ static void blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,
 	INIT_LIST_HEAD(&rq->queuelist);
 }
 
+static bool bio_unaligned(const struct bio *bio,
+		const struct request_queue *q)
+{
+	unsigned int bs = queue_logical_block_size(q);
+
+	if (bio->bi_iter.bi_size & (bs - 1))
+		return true;
+
+	if (bio->bi_iter.bi_size &&
+	    ((bio->bi_iter.bi_sector << SECTOR_SHIFT) & (bs - 1)))
+		return true;
+
+	return false;
+}
+
 /**
  * blk_mq_submit_bio - Create and send a request to block device.
  * @bio: Bio pointer.
@@ -2966,6 +2981,15 @@ void blk_mq_submit_bio(struct bio *bio)
 			return;
 	}
 
+	/*
+	 * Device reconfiguration may change logical block size, so alignment
+	 * check has to be done with queue usage counter held
+	 */
+	if (unlikely(bio_unaligned(bio, q))) {
+		bio_io_error(bio);
+		goto queue_exit;
+	}
+
 	if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
 		bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
 		if (!bio)
-- 
2.44.0