[PATCH v4 3/7] block: Introduce blk_queue_get_max_write_zeroes_sectors()

[Kirill Tkhai <ktkhai@virtuozzo.com>]

This introduces a new primitive, which returns max sectors
for REQ_OP_WRITE_ZEROES operation.
@op_flags is unused now, and it will be enabled in next patch.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 block/blk-core.c       |    2 +-
 block/blk-merge.c      |    9 ++++++---
 include/linux/blkdev.h |    8 +++++++-
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index ac2634bcda1f..2edcd55624f1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -978,7 +978,7 @@ generic_make_request_checks(struct bio *bio)
 			goto not_supported;
 		break;
 	case REQ_OP_WRITE_ZEROES:
-		if (!q->limits.max_write_zeroes_sectors)
+		if (!blk_queue_get_max_write_zeroes_sectors(q, bio->bi_opf))
 			goto not_supported;
 		break;
 	default:
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 1534ed736363..467b292bc6e8 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -105,15 +105,18 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
 		struct bio *bio, struct bio_set *bs, unsigned *nsegs)
 {
+	unsigned int max_sectors;
+
+	max_sectors = blk_queue_get_max_write_zeroes_sectors(q, bio->bi_opf);
 	*nsegs = 0;
 
-	if (!q->limits.max_write_zeroes_sectors)
+	if (!max_sectors)
 		return NULL;
 
-	if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
+	if (bio_sectors(bio) <= max_sectors)
 		return NULL;
 
-	return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
+	return bio_split(bio, max_sectors, GFP_NOIO, bs);
 }
 
 static struct bio *blk_bio_write_same_split(struct request_queue *q,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 23a5850f35f6..264202fa3bf8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -988,6 +988,12 @@ static inline struct bio_vec req_bvec(struct request *rq)
 	return mp_bvec_iter_bvec(rq->bio->bi_io_vec, rq->bio->bi_iter);
 }
 
+static inline unsigned int blk_queue_get_max_write_zeroes_sectors(
+		struct request_queue *q, unsigned int op_flags)
+{
+	return q->limits.max_write_zeroes_sectors;
+}
+
 static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
 						     unsigned int op_flags)
 {
@@ -1001,7 +1007,7 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
 		return q->limits.max_write_same_sectors;
 
 	if (unlikely(op == REQ_OP_WRITE_ZEROES))
-		return q->limits.max_write_zeroes_sectors;
+		return blk_queue_get_max_write_zeroes_sectors(q, op_flags);
 
 	return q->limits.max_sectors;
 }