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@xxxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/bfq-iosched.c | 3 +++
block/blk-merge.c | 16 ----------------
block/elevator.c | 3 +++
block/mq-deadline-main.c | 2 ++
include/linux/blkdev.h | 16 ++++++++++++++++
5 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 727955918563..673a634eadd9 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2361,6 +2361,9 @@ 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 a11b3b53717e..f8707ff7e2fc 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -705,22 +705,6 @@ static void blk_account_io_merge_request(struct request *req)
}
}
-/*
- * 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 52ada14cfe45..a5fe2615ec0f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -336,6 +336,9 @@ 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-main.c b/block/mq-deadline-main.c
index 6f612e6dc82b..294be0c0db65 100644
--- a/block/mq-deadline-main.c
+++ b/block/mq-deadline-main.c
@@ -677,6 +677,8 @@ 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 3177181c4326..87f00292fd7a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1521,6 +1521,22 @@ 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);
--
2.31.1
