block: prevent request-to-request merging with gaps if not allowed

If the queue has SG_GAPS set, we must not merge across an sg gap. This is caught for the bio case, but currently not for the more rare case of merging two requests directly. Signed-off-by: Keith Busch <[email protected]> Cut the dm bits, those will go through the dm tree, and fixed the test_bit() test. Signed-off-by: Jens Axboe <[email protected]>
ambv · Feb 11, 2015 · 854fbb9 · 854fbb9
1 parent 201f201
commit 854fbb9
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/block/blk-merge.c b/block/blk-merge.c
@@ -385,6 +385,14 @@ static bool req_no_special_merge(struct request *req)
 	return !q->mq_ops && req->special;
 }
 
+static int req_gap_to_prev(struct request *req, struct request *next)
+{
+	struct bio *prev = req->biotail;
+
+	return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1],
+				next->bio->bi_io_vec[0].bv_offset);
+}
+
 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 				struct request *next)
 {
@@ -399,6 +407,10 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 	if (req_no_special_merge(req) || req_no_special_merge(next))
 		return 0;
 
+	if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) &&
+	    req_gap_to_prev(req, next))
+		return 0;
+
 	/*
 	 * Will it become too large?
 	 */