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Date:   Thu,  4 Feb 2021 10:01:56 +0900
From:   Changheun Lee <>
Cc:,,,,,,, Changheun Lee <>
Subject: [PATCH v5 2/2] bio: add limit_bio_size sysfs

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

Signed-off-by: Changheun Lee <>
 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 <>
+		(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 2638d3446b79..cd371a821855 100644
--- a/Documentation/block/queue-sysfs.rst
+++ b/Documentation/block/queue-sysfs.rst
@@ -273,4 +273,11 @@ devices are described in the ZBC (Zoned Block Commands) and ZAC
 do not support zone commands, they will be treated as regular block devices
 and zoned will report "none".
+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 <>, February 2009
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b513f1683af0..840d97f427e6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -288,6 +288,7 @@ QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
+QUEUE_SYSFS_BIT_FNS(limit_bio_size, LIMIT_BIO_SIZE, 0);
 static ssize_t queue_zoned_show(struct request_queue *q, char *page)
@@ -615,6 +616,7 @@ 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[] = {
@@ -648,6 +650,7 @@ static struct attribute *queue_attrs[] = {
+	&queue_limit_bio_size_entry.attr,

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