1 files changed, 43 insertions, 0 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index e1999679a4d5..7c9ca01baa45 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -311,6 +311,36 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
         return 1;
 }
 
+/**
+ * blk_rq_set_mixed_merge - mark a request as mixed merge
+ * @rq: request to mark as mixed merge
+ *
+ * Description:
+ *     @rq is about to be mixed merged.  Make sure the attributes
+ *     which can be mixed are set in each bio and mark @rq as mixed
+ *     merged.
+ */
+void blk_rq_set_mixed_merge(struct request *rq)
+{
+        unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
+        struct bio *bio;
+
+        if (rq->cmd_flags & REQ_MIXED_MERGE)
+                return;
+
+        /*
+         * @rq will no longer represent mixable attributes for all the
+         * contained bios.  It will just track those of the first one.
+         * Distributes the attributs to each bio.
+         */
+        for (bio = rq->bio; bio; bio = bio->bi_next) {
+                WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
+                             (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
+                bio->bi_rw |= ff;
+        }
+        rq->cmd_flags |= REQ_MIXED_MERGE;
+}
+
 static void blk_account_io_merge(struct request *req)
 {
         if (blk_do_io_stat(req)) {
@@ -366,6 +396,19 @@ static int attempt_merge(struct request_queue *q, struct request *req,
                 return 0;
 
         /*
+         * If failfast settings disagree or any of the two is already
+         * a mixed merge, mark both as mixed before proceeding.  This
+         * makes sure that all involved bios have mixable attributes
+         * set properly.
+         */
+        if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
+            (req->cmd_flags & REQ_FAILFAST_MASK) !=
+            (next->cmd_flags & REQ_FAILFAST_MASK)) {
+                blk_rq_set_mixed_merge(req);
+                blk_rq_set_mixed_merge(next);
+        }
+
+        /*
          * At this point we have either done a back merge
          * or front merge. We need the smaller start_time of
          * the merged requests to be the current request