[PATCH v6 3/3] bio: add limit_bio_size sysfs

[Changheun Lee]

Add limit_bio_size block sysfs node to limit bio size.
Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size is set.
And bio max size will be limited by queue max sectors via
QUEUE_FLAG_LIMIT_BIO_SIZE set.

Signed-off-by: Changheun Lee <nanich.lee@xxxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-block | 10 ++++++++++
 Documentation/block/queue-sysfs.rst   |  7 +++++++
 block/blk-sysfs.c                     |  3 +++
 3 files changed, 20 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index e34cdeeeb9d4..86a7b15410cf 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -316,3 +316,13 @@ Description:
 		does not complete in this time then the block driver timeout
 		handler is invoked. That timeout handler can decide to retry
 		the request, to fail it or to start a device recovery strategy.
+
+What:		/sys/block/<disk>/queue/limit_bio_size
+Date:		Feb, 2021
+Contact:	Changheun Lee <nanich.lee@xxxxxxxxxxx>
+Description:
+		(RW) Toggle for set/clear QUEUE_FLAG_LIMIT_BIO_SIZE queue flag.
+		Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size
+		is set. And bio max size will be limited by queue max sectors.
+		QUEUE_FLAG_LIMIT_BIO_SIZE will be cleared if limit_bio_size is
+		cleard. And limit of bio max size will be cleard.
diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
index 4dc7f0d499a8..220d183a4c11 100644
--- a/Documentation/block/queue-sysfs.rst
+++ b/Documentation/block/queue-sysfs.rst
@@ -286,4 +286,11 @@ sequential zones of zoned block devices (devices with a zoned attributed
 that reports "host-managed" or "host-aware"). This value is always 0 for
 regular block devices.
 
+limit_bio_size (RW)
+-------------------
+This indicates QUEUE_FLAG_LIMIT_BIO_SIZE queue flag value. And
+QUEUE_FLAG_LIMIT_BIO_SIZE can be changed via set(1)/clear(0) this node.
+bio max size will be limited by queue max sectors via set this node. And
+limit of bio max size will be cleard via clear this node.
+
 Jens Axboe <jens.axboe@xxxxxxxxxx>, February 2009
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 0f4f0c8a7825..4625d5319daf 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -294,6 +294,7 @@ QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
 QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
 QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
 QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
+QUEUE_SYSFS_BIT_FNS(limit_bio_size, LIMIT_BIO_SIZE, 0);
 #undef QUEUE_SYSFS_BIT_FNS
 
 static ssize_t queue_zoned_show(struct request_queue *q, char *page)
@@ -625,6 +626,7 @@ QUEUE_RW_ENTRY(queue_nonrot, "rotational");
 QUEUE_RW_ENTRY(queue_iostats, "iostats");
 QUEUE_RW_ENTRY(queue_random, "add_random");
 QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes");
+QUEUE_RW_ENTRY(queue_limit_bio_size, "limit_bio_size");
 
 static struct attribute *queue_attrs[] = {
 	&queue_requests_entry.attr,
@@ -659,6 +661,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_rq_affinity_entry.attr,
 	&queue_iostats_entry.attr,
 	&queue_stable_writes_entry.attr,
+	&queue_limit_bio_size_entry.attr,
 	&queue_random_entry.attr,
 	&queue_poll_entry.attr,
 	&queue_wc_entry.attr,
-- 
2.29.0