block: return ELEVATOR_DISCARD_MERGE if possible

commit 866663b7b52d2da267b28e12eed89ee781b8fed1 upstream.

When merging one bio to request, if they are discard IO and the queue
supports multi-range discard, we need to return ELEVATOR_DISCARD_MERGE
because both block core and related drivers(nvme, virtio-blk) doesn't
handle mixed discard io merge(traditional IO merge together with
discard merge) well.

Fix the issue by returning ELEVATOR_DISCARD_MERGE in this situation,
so both blk-mq and drivers just need to handle multi-range discard.

Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Fixes: 2705dfb20947 ("block: fix discard request merge")
Link: https://lore.kernel.org/r/20210729034226.1591070-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 1d443d17cf7c5ec31ff13ff88c903064a03b3d29..d46806182b05169874231c9d941f60f3af7493d7 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2251,6 +2251,9 @@ static int bfq_request_merge(struct request_queue *q, struct request **req,
        __rq = bfq_find_rq_fmerge(bfqd, bio, q);
        if (__rq && elv_bio_merge_ok(__rq, bio)) {
                *req = __rq;
+
+               if (blk_discard_mergable(__rq))
+                       return ELEVATOR_DISCARD_MERGE;
                return ELEVATOR_FRONT_MERGE;
        }
 

diff --git a/block/blk-merge.c b/block/blk-merge.c
index a62692d135660a596790cf4b821fcf5410be0e0e..5219064cd72bb026b577765337bd8e73bba5f609 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -721,21 +721,6 @@ static void blk_account_io_merge(struct request *req)
                part_stat_unlock();
        }
 }
-/*
- * Two cases of handling DISCARD merge:
- * If max_discard_segments > 1, the driver takes every bio
- * as a range and send them to controller together. The ranges
- * needn't to be contiguous.
- * Otherwise, the bios/requests will be handled as same as
- * others which should be contiguous.
- */
-static inline bool blk_discard_mergable(struct request *req)
-{
-       if (req_op(req) == REQ_OP_DISCARD &&
-           queue_max_discard_segments(req->q) > 1)
-               return true;
-       return false;
-}
 
 static enum elv_merge blk_try_req_merge(struct request *req,
                                        struct request *next)

diff --git a/block/elevator.c b/block/elevator.c
index 78805c74ea8a4b42d21134db8399cdcbdfc368a1..3ba826230c5784a8c347b63e6b6a6490c72dedb8 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -337,6 +337,9 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req,
        __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
        if (__rq && elv_bio_merge_ok(__rq, bio)) {
                *req = __rq;
+
+               if (blk_discard_mergable(__rq))
+                       return ELEVATOR_DISCARD_MERGE;
                return ELEVATOR_BACK_MERGE;
        }
 

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 19c6922e85f1b149f78913c0e923f5a464ea4cdf..6d6dda5cfffa3b4c9ab7ca9211dd0ef6a11fc07f 100644 (file)
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -452,6 +452,8 @@ static int dd_request_merge(struct request_queue *q, struct request **rq,
 
                if (elv_bio_merge_ok(__rq, bio)) {
                        *rq = __rq;
+                       if (blk_discard_mergable(__rq))
+                               return ELEVATOR_DISCARD_MERGE;
                        return ELEVATOR_FRONT_MERGE;
                }
        }

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8cc766743270fd824a1f37647f91e17de5bdeea0..308c2d8cdca1923d96d557524bc65a95e387c21d 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1409,6 +1409,22 @@ static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector
        return offset << SECTOR_SHIFT;
 }
 
+/*
+ * Two cases of handling DISCARD merge:
+ * If max_discard_segments > 1, the driver takes every bio
+ * as a range and send them to controller together. The ranges
+ * needn't to be contiguous.
+ * Otherwise, the bios/requests will be handled as same as
+ * others which should be contiguous.
+ */
+static inline bool blk_discard_mergable(struct request *req)
+{
+       if (req_op(req) == REQ_OP_DISCARD &&
+           queue_max_discard_segments(req->q) > 1)
+               return true;
+       return false;
+}
+
 static inline int bdev_discard_alignment(struct block_device *bdev)
 {
        struct request_queue *q = bdev_get_queue(bdev);