Merge tag 'block-5.13-2021-05-22' of git://git.kernel.dk/linux-block

[linux-2.6-microblaze.git] / block / bfq-iosched.c

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0270cd7..acd1f88 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -372,9 +372,38 @@ struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync)
        return bic->bfqq[is_sync];
 }
 
+static void bfq_put_stable_ref(struct bfq_queue *bfqq);
+
 void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync)
 {
+       /*
+        * If bfqq != NULL, then a non-stable queue merge between
+        * bic->bfqq and bfqq is happening here. This causes troubles
+        * in the following case: bic->bfqq has also been scheduled
+        * for a possible stable merge with bic->stable_merge_bfqq,
+        * and bic->stable_merge_bfqq == bfqq happens to
+        * hold. Troubles occur because bfqq may then undergo a split,
+        * thereby becoming eligible for a stable merge. Yet, if
+        * bic->stable_merge_bfqq points exactly to bfqq, then bfqq
+        * would be stably merged with itself. To avoid this anomaly,
+        * we cancel the stable merge if
+        * bic->stable_merge_bfqq == bfqq.
+        */
        bic->bfqq[is_sync] = bfqq;
+
+       if (bfqq && bic->stable_merge_bfqq == bfqq) {
+               /*
+                * Actually, these same instructions are executed also
+                * in bfq_setup_cooperator, in case of abort or actual
+                * execution of a stable merge. We could avoid
+                * repeating these instructions there too, but if we
+                * did so, we would nest even more complexity in this
+                * function.
+                */
+               bfq_put_stable_ref(bic->stable_merge_bfqq);
+
+               bic->stable_merge_bfqq = NULL;
+       }
 }
 
 struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic)
@@ -2263,10 +2292,9 @@ static void bfq_remove_request(struct request_queue *q,
 
 }
 
-static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
+static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
                unsigned int nr_segs)
 {
-       struct request_queue *q = hctx->queue;
        struct bfq_data *bfqd = q->elevator->elevator_data;
        struct request *free = NULL;
        /*
@@ -2631,8 +2659,6 @@ static bool bfq_may_be_close_cooperator(struct bfq_queue *bfqq,
 static bool idling_boosts_thr_without_issues(struct bfq_data *bfqd,
                                             struct bfq_queue *bfqq);
 
-static void bfq_put_stable_ref(struct bfq_queue *bfqq);
-
 /*
  * Attempt to schedule a merge of bfqq with the currently in-service
  * queue or with a close queue among the scheduled queues.  Return