diff --git a/block/blk-core.c b/block/blk-core.c
index 00e053c704a186c624ef2a710cac2d5e3ff843d7..c0e4d41d3d3336d8a40c8d5fdd29325b0fce9fe2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1483,6 +1483,30 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
return true;
}
+bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
+ struct bio *bio)
+{
+ 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(bio) >
+ blk_rq_get_max_sectors(req, blk_rq_pos(req)))
+ goto no_merge;
+
+ req->biotail->bi_next = bio;
+ req->biotail = bio;
+ req->__data_len += bio->bi_iter.bi_size;
+ req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
+ req->nr_phys_segments = segments + 1;
+
+ blk_account_io_start(req, false);
+ return true;
+no_merge:
+ req_set_nomerge(q, req);
+ return false;
+}
+
/**
* blk_attempt_plug_merge - try to merge with %current's plugged list
* @q: request_queue new bio is being queued at
@@ -1547,6 +1571,9 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
case ELEVATOR_FRONT_MERGE:
merged = bio_attempt_front_merge(q, rq, bio);
break;
+ case ELEVATOR_DISCARD_MERGE:
+ merged = bio_attempt_discard_merge(q, rq, bio);
+ break;
default:
break;
}
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6cbd90ad5f903379b501545868da1528a8dea6b3..2afa262425d102e5c1500912f3b6d77525754566 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -803,7 +803,10 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
{
- if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
+ if (req_op(rq) == REQ_OP_DISCARD &&
+ queue_max_discard_segments(rq->q) > 1)
+ return ELEVATOR_DISCARD_MERGE;
+ else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
return ELEVATOR_BACK_MERGE;
else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
return ELEVATOR_FRONT_MERGE;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index dd9722df4afe7820e5be50f9dd770f0204739112..7412191aee5762d89a0b2dcce10aefbbe89784d5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -780,6 +780,9 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
if (blk_mq_sched_allow_merge(q, rq, bio))
merged = bio_attempt_front_merge(q, rq, bio);
break;
+ case ELEVATOR_DISCARD_MERGE:
+ merged = bio_attempt_discard_merge(q, rq, bio);
+ break;
default:
continue;
}
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 6eb19bcbf3cb7a295cfd5c28cac12fb6b24d65c2..1e7174ffc9d49d0757cf7cb7da1ffe822f7fbbd6 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -88,6 +88,7 @@ EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
void blk_set_default_limits(struct queue_limits *lim)
{
lim->max_segments = BLK_MAX_SEGMENTS;
+ lim->max_discard_segments = 1;
lim->max_integrity_segments = 0;
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
lim->virt_boundary_mask = 0;
@@ -128,6 +129,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
/* Inherit limits from component devices */
lim->discard_zeroes_data = 1;
lim->max_segments = USHRT_MAX;
+ lim->max_discard_segments = 1;
lim->max_hw_sectors = UINT_MAX;
lim->max_segment_size = UINT_MAX;
lim->max_sectors = UINT_MAX;
@@ -336,6 +338,22 @@ void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments
}
EXPORT_SYMBOL(blk_queue_max_segments);
+/**
+ * blk_queue_max_discard_segments - set max segments for discard requests
+ * @q: the request queue for the device
+ * @max_segments: max number of segments
+ *
+ * Description:
+ * Enables a low level driver to set an upper limit on the number of
+ * segments in a discard request.
+ **/
+void blk_queue_max_discard_segments(struct request_queue *q,
+ unsigned short max_segments)
+{
+ q->limits.max_discard_segments = max_segments;
+}
+EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments);
+
/**
* blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
* @q: the request queue for the device
@@ -553,6 +571,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
b->virt_boundary_mask);
t->max_segments = min_not_zero(t->max_segments, b->max_segments);
+ t->max_discard_segments = min_not_zero(t->max_discard_segments,
+ b->max_discard_segments);
t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
b->max_integrity_segments);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 48032c4759a7d800028329b7785d96870cb16c9c..070d81bae1d50af56fbc4d1a6135b54e7ede82f8 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -121,6 +121,12 @@ static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
return queue_var_show(queue_max_segments(q), (page));
}
+static ssize_t queue_max_discard_segments_show(struct request_queue *q,
+ char *page)
+{
+ return queue_var_show(queue_max_discard_segments(q), (page));
+}
+
static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
{
return queue_var_show(q->limits.max_integrity_segments, (page));
@@ -545,6 +551,11 @@ static struct queue_sysfs_entry queue_max_segments_entry = {
.show = queue_max_segments_show,
};
+static struct queue_sysfs_entry queue_max_discard_segments_entry = {
+ .attr = {.name = "max_discard_segments", .mode = S_IRUGO },
+ .show = queue_max_discard_segments_show,
+};
+
static struct queue_sysfs_entry queue_max_integrity_segments_entry = {
.attr = {.name = "max_integrity_segments", .mode = S_IRUGO },
.show = queue_max_integrity_segments_show,
@@ -697,6 +708,7 @@ static struct attribute *default_attrs[] = {
&queue_max_hw_sectors_entry.attr,
&queue_max_sectors_entry.attr,
&queue_max_segments_entry.attr,
+ &queue_max_discard_segments_entry.attr,
&queue_max_integrity_segments_entry.attr,
&queue_max_segment_size_entry.attr,
&queue_iosched_entry.attr,
diff --git a/block/blk.h b/block/blk.h
index ae82f2ac4019468b9276da43b95c6b4bacdc4ce7..d1ea4bd9b9a3f8f24eba17f4e35fbddaebd23c7d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -100,6 +100,8 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
struct bio *bio);
bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
struct bio *bio);
+bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
+ struct bio *bio);
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
unsigned int *request_count,
struct request **same_queue_rq);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e0bac14347e6e0c368b747f243289ba4cafb304e..aecca0e7d9cadb04c368fbac010ae7dacc831c90 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -331,6 +331,7 @@ struct queue_limits {
unsigned short logical_block_size;
unsigned short max_segments;
unsigned short max_integrity_segments;
+ unsigned short max_discard_segments;
unsigned char misaligned;
unsigned char discard_misaligned;
@@ -1146,6 +1147,8 @@ extern void blk_queue_bounce_limit(struct request_queue *, u64);
extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
extern void blk_queue_chunk_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_segments(struct request_queue *, unsigned short);
+extern void blk_queue_max_discard_segments(struct request_queue *,
+ unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors);
@@ -1189,6 +1192,15 @@ extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);
extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);
+/*
+ * Number of physical segments as sent to the device.
+ *
+ * Normally this is the number of discontiguous data segments sent by the
+ * submitter. But for data-less command like discard we might have no
+ * actual data segments submitted, but the driver might have to add it's
+ * own special payload. In that case we still return 1 here so that this
+ * special payload will be mapped.
+ */
static inline unsigned short blk_rq_nr_phys_segments(struct request *rq)
{
if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
@@ -1196,6 +1208,15 @@ static inline unsigned short blk_rq_nr_phys_segments(struct request *rq)
return rq->nr_phys_segments;
}
+/*
+ * Number of discard segments (or ranges) the driver needs to fill in.
+ * Each discard bio merged into a request is counted as one segment.
+ */
+static inline unsigned short blk_rq_nr_discard_segments(struct request *rq)
+{
+ return max_t(unsigned short, rq->nr_phys_segments, 1);
+}
+
extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
extern void blk_dump_rq_flags(struct request *, char *);
extern long nr_blockdev_pages(void);
@@ -1384,6 +1405,11 @@ static inline unsigned short queue_max_segments(struct request_queue *q)
return q->limits.max_segments;
}
+static inline unsigned short queue_max_discard_segments(struct request_queue *q)
+{
+ return q->limits.max_discard_segments;
+}
+
static inline unsigned int queue_max_segment_size(struct request_queue *q)
{
return q->limits.max_segment_size;
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index b38b4e651ea6dab2aedee6bc158797c81fe482b3..8265b6330cc2a42162c98ea299167321543c26f5 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -16,6 +16,7 @@ enum elv_merge {
ELEVATOR_NO_MERGE = 0,
ELEVATOR_FRONT_MERGE = 1,
ELEVATOR_BACK_MERGE = 2,
+ ELEVATOR_DISCARD_MERGE = 3,
};
typedef enum elv_merge (elevator_merge_fn) (struct request_queue *, struct request **,