[PATCH V2 3/4] block: add io_extra_stats node

[Guoqing Jiang <guoqing.jiang@cloud.ionos.com>]

If user doesn't care about the size and latency of io, and they could
suffer from the additional overhead. So introduce a specific sysfs node
to avoid such mistake.

Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
---
 Documentation/ABI/testing/sysfs-block | 9 +++++++++
 Documentation/block/queue-sysfs.rst   | 5 +++++
 block/blk-sysfs.c                     | 3 +++
 include/linux/blkdev.h                | 2 ++
 4 files changed, 19 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 0ffb63469772..e1611c62a3e1 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -333,3 +333,12 @@ 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/io_extra_stats
+Date:		January 2021
+Contact:	Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
+Description:
+		Indicates if people want to know the extra statistics (I/O
+		size and I/O latency) from /sys/block/<disk>/io_latency
+		and /sys/block/<disk>/io_size. The value is 0 by default,
+		set if the extra statistics are needed.
diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
index 2638d3446b79..28ffce653eb1 100644
--- a/Documentation/block/queue-sysfs.rst
+++ b/Documentation/block/queue-sysfs.rst
@@ -99,6 +99,11 @@ iostats (RW)
 This file is used to control (on/off) the iostats accounting of the
 disk.
 
+io_extra_stats (RW)
+-------------------
+This file is used to control (on/off) the additional accounting of the
+io size and io latency of disk.
+
 logical_block_size (RO)
 -----------------------
 This is the logical block size of the device, in bytes.
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b513f1683af0..ed31938e89fe 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -287,6 +287,7 @@ queue_##name##_store(struct request_queue *q, const char *page, size_t count) \
 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(io_extra_stats, IO_EXTRA_STAT, 0);
 QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
 #undef QUEUE_SYSFS_BIT_FNS
 
@@ -613,6 +614,7 @@ static struct queue_sysfs_entry queue_hw_sector_size_entry = {
 
 QUEUE_RW_ENTRY(queue_nonrot, "rotational");
 QUEUE_RW_ENTRY(queue_iostats, "iostats");
+QUEUE_RW_ENTRY(queue_io_extra_stats, "io_extra_stats");
 QUEUE_RW_ENTRY(queue_random, "add_random");
 QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes");
 
@@ -647,6 +649,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_nomerges_entry.attr,
 	&queue_rq_affinity_entry.attr,
 	&queue_iostats_entry.attr,
+	&queue_io_extra_stats_entry.attr,
 	&queue_stable_writes_entry.attr,
 	&queue_random_entry.attr,
 	&queue_poll_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0dea268bd61b..62881db2004f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -621,6 +621,7 @@ struct request_queue {
 #define QUEUE_FLAG_RQ_ALLOC_TIME 27	/* record rq->alloc_time_ns */
 #define QUEUE_FLAG_HCTX_ACTIVE	28	/* at least one blk-mq hctx is active */
 #define QUEUE_FLAG_NOWAIT       29	/* device supports NOWAIT */
+#define QUEUE_FLAG_IO_EXTRA_STAT 30	/* extra IO accounting for size and latency */
 
 #define QUEUE_FLAG_MQ_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_SAME_COMP) |		\
@@ -641,6 +642,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
 #define blk_queue_stable_writes(q) \
 	test_bit(QUEUE_FLAG_STABLE_WRITES, &(q)->queue_flags)
 #define blk_queue_io_stat(q)	test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
+#define blk_queue_io_extra_stat(q) test_bit(QUEUE_FLAG_IO_EXTRA_STAT, &(q)->queue_flags)
 #define blk_queue_add_random(q)	test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
 #define blk_queue_discard(q)	test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
 #define blk_queue_zone_resetall(q)	\
-- 
2.17.1