[PATCH v4 03/10] block: introduce blk_req_zone_write_trylock

[Johannes Thumshirn <johannes.thumshirn@wdc.com>]

Introduce blk_req_zone_write_trylock(), which either grabs the write-lock
for a sequential zone or returns false, if the zone is already locked.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-zoned.c      | 14 ++++++++++++++
 include/linux/blkdev.h |  1 +
 2 files changed, 15 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 05741c6f618b..00b025b8b7c0 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -50,6 +50,20 @@ bool blk_req_needs_zone_write_lock(struct request *rq)
 }
 EXPORT_SYMBOL_GPL(blk_req_needs_zone_write_lock);
 
+bool blk_req_zone_write_trylock(struct request *rq)
+{
+	unsigned int zno = blk_rq_zone_no(rq);
+
+	if (test_and_set_bit(zno, rq->q->seq_zones_wlock))
+		return false;
+
+	WARN_ON_ONCE(rq->rq_flags & RQF_ZONE_WRITE_LOCKED);
+	rq->rq_flags |= RQF_ZONE_WRITE_LOCKED;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(blk_req_zone_write_trylock);
+
 void __blk_req_zone_write_lock(struct request *rq)
 {
 	if (WARN_ON_ONCE(test_and_set_bit(blk_rq_zone_no(rq),
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 36111b10d514..e591b22ace03 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1746,6 +1746,7 @@ extern int bdev_write_page(struct block_device *, sector_t, struct page *,
 
 #ifdef CONFIG_BLK_DEV_ZONED
 bool blk_req_needs_zone_write_lock(struct request *rq);
+bool blk_req_zone_write_trylock(struct request *rq);
 void __blk_req_zone_write_lock(struct request *rq);
 void __blk_req_zone_write_unlock(struct request *rq);
 
-- 
2.24.1