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 <keith.busch@intel.com>
Cut the dm bits, those will go through the dm tree, and fixed
the test_bit() test.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 89b97b5e0881853054c0807c5607c20d91d90762..9476b1528ded0c319efe31b95a10d3c002702298 100644 (file)
--- 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?
         */