[PATCH 12/12] block: export and document bit_bucket attribute

[Keith Busch]

From: Keith Busch <kbusch at kernel.org>

Now that user space applications can make use of partial sector reads,
export and document the queue attribute that indicates if the capability
is supported.

Signed-off-by: Keith Busch <kbusch at kernel.org>
---
 Documentation/ABI/stable/sysfs-block | 9 +++++++++
 block/blk-sysfs.c                    | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index cd14ecb3c9a5..defc056690d0 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -142,6 +142,15 @@ Description:
 		Default value of this file is '1'(on).
 
 
+What:		/sys/block/<disk>/queue/bit_bucket
+Date:		June 2022
+Contact:	linux-block at vger.kernel.org
+Description:
+		[RO] This file indicates if the device supports partial sector
+		reads.  If set to '1', user space can issue direct IO reads at
+		dma_alignment granularity.
+
+
 What:		/sys/block/<disk>/queue/chunk_sectors
 Date:		September 2016
 Contact:	Hannes Reinecke <hare at suse.com>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 85ea43eff094..0c1f1c2fbb30 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -309,6 +309,7 @@ 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(bit_bucket, BIT_BUCKET, 0);
 #undef QUEUE_SYSFS_BIT_FNS
 
 static ssize_t queue_zoned_show(struct request_queue *q, char *page)
@@ -627,6 +628,7 @@ 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_bit_bucket, "bit_bucket");
 
 static struct attribute *queue_attrs[] = {
 	&queue_requests_entry.attr,
@@ -653,6 +655,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_zone_append_max_entry.attr,
 	&queue_zone_write_granularity_entry.attr,
 	&queue_nonrot_entry.attr,
+	&queue_bit_bucket_entry.attr,
 	&queue_zoned_entry.attr,
 	&queue_nr_zones_entry.attr,
 	&queue_max_open_zones_entry.attr,
-- 
2.30.2