* [PATCHv2 1/2] block: Merge discard requests as a special case
2018-02-01 20:31 [PATCHv2 0/2] block: Discard merging fixes Keith Busch
@ 2018-02-01 20:31 ` Keith Busch
2018-02-01 21:00 ` Jens Axboe
2018-02-01 20:31 ` [PATCHv2 2/2] block: Handle merging discards in IO schedulers Keith Busch
1 sibling, 1 reply; 6+ messages in thread
From: Keith Busch @ 2018-02-01 20:31 UTC (permalink / raw)
To: Linux Block, Linux NVMe, Christoph Hellwig, Jens Axboe; +Cc: Keith Busch
Discard requests operate under different constraints than other operations
and have different rules for merging. This patch will handle such requests
as a special case, using the same criteria and segment accounting used
for merging a discard bio into a reqseut.
Signed-off-by: Keith Busch <keith.busch@intel.com>
---
block/blk-merge.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 8452fc7164cc..e36462bc90f3 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -550,6 +550,25 @@ static bool req_no_special_merge(struct request *req)
return !q->mq_ops && req->special;
}
+static int req_attempt_discard_merge(struct request_queue *q, struct request *req,
+ struct request *next)
+{
+ unsigned short segments = blk_rq_nr_discard_segments(req);
+
+ if (segments >= queue_max_discard_segments(q))
+ goto no_merge;
+ if (blk_rq_sectors(req) + bio_sectors(next->bio) >
+ blk_rq_get_max_sectors(req, blk_rq_pos(req)))
+ goto no_merge;
+
+ req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
+ return 1;
+
+no_merge:
+ req_set_nomerge(q, req);
+ return 0;
+}
+
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
struct request *next)
{
@@ -564,6 +583,13 @@ 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;
+ /*
+ * Merging discard requests use different constraints than other
+ * operations.
+ */
+ if (req_op(req) == REQ_OP_DISCARD)
+ return req_attempt_discard_merge(q, req, next);
+
if (req_gap_back_merge(req, next->bio))
return 0;
@@ -715,7 +741,8 @@ static struct request *attempt_merge(struct request_queue *q,
req->__data_len += blk_rq_bytes(next);
- elv_merge_requests(q, req, next);
+ if (req_op(req) != REQ_OP_DISCARD)
+ elv_merge_requests(q, req, next);
/*
* 'next' is going away, so update stats accordingly
--
2.14.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCHv2 2/2] block: Handle merging discards in IO schedulers
2018-02-01 20:31 [PATCHv2 0/2] block: Discard merging fixes Keith Busch
2018-02-01 20:31 ` [PATCHv2 1/2] block: Merge discard requests as a special case Keith Busch
@ 2018-02-01 20:31 ` Keith Busch
2018-02-01 21:02 ` Jens Axboe
1 sibling, 1 reply; 6+ messages in thread
From: Keith Busch @ 2018-02-01 20:31 UTC (permalink / raw)
To: Linux Block, Linux NVMe, Christoph Hellwig, Jens Axboe; +Cc: Keith Busch
This adds support for merging discard requests in all IO schedulers.
Signed-off-by: Keith Busch <keith.busch@intel.com>
---
block/bfq-iosched.c | 2 +-
block/blk-core.c | 4 ++++
block/blk-mq-sched.c | 2 ++
block/cfq-iosched.c | 2 +-
block/deadline-iosched.c | 4 +++-
block/elevator.c | 2 +-
block/mq-deadline.c | 2 +-
7 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 47e6ec7427c4..9b08c08298a6 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1839,7 +1839,7 @@ 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;
- return ELEVATOR_FRONT_MERGE;
+ return blk_try_merge(__rq, bio);
}
return ELEVATOR_NO_MERGE;
diff --git a/block/blk-core.c b/block/blk-core.c
index a2005a485335..295ce3cbe1f6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1952,6 +1952,10 @@ static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
else
elv_merged_request(q, req, ELEVATOR_FRONT_MERGE);
goto out_unlock;
+ case ELEVATOR_DISCARD_MERGE:
+ if (!bio_attempt_discard_merge(q, req, bio))
+ break;
+ goto out_unlock;
default:
break;
}
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 55c0a745b427..25c14c58385c 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -259,6 +259,8 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
if (!*merged_request)
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
return true;
+ case ELEVATOR_DISCARD_MERGE:
+ return bio_attempt_discard_merge(q, rq, bio);
default:
return false;
}
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9f342ef1ad42..38158873d775 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2518,7 +2518,7 @@ static enum elv_merge cfq_merge(struct request_queue *q, struct request **req,
__rq = cfq_find_rq_fmerge(cfqd, bio);
if (__rq && elv_bio_merge_ok(__rq, bio)) {
*req = __rq;
- return ELEVATOR_FRONT_MERGE;
+ return blk_try_merge(__rq, bio);
}
return ELEVATOR_NO_MERGE;
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 9de9f156e203..849e03938653 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -14,6 +14,8 @@
#include <linux/compiler.h>
#include <linux/rbtree.h>
+#include "blk.h"
+
/*
* See Documentation/block/deadline-iosched.txt
*/
@@ -142,7 +144,7 @@ deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
if (elv_bio_merge_ok(__rq, bio)) {
*req = __rq;
- return ELEVATOR_FRONT_MERGE;
+ return blk_try_merge(__rq, bio);
}
}
}
diff --git a/block/elevator.c b/block/elevator.c
index e87e9b43aba0..7fd6cb9cfec1 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -484,7 +484,7 @@ 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;
- return ELEVATOR_BACK_MERGE;
+ return blk_try_merge(__rq, bio);
}
if (e->uses_mq && e->type->ops.mq.request_merge)
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index c56f211c8440..a0f5752b6858 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -451,7 +451,7 @@ static int dd_request_merge(struct request_queue *q, struct request **rq,
if (elv_bio_merge_ok(__rq, bio)) {
*rq = __rq;
- return ELEVATOR_FRONT_MERGE;
+ return blk_try_merge(__rq, bio);
}
}
--
2.14.3
^ permalink raw reply related [flat|nested] 6+ messages in thread