[PATCHv12 05/12] block: introduce a write_stream_granularity queue limit

[Keith Busch <kbusch@meta.com>]

From: Christoph Hellwig <hch@lst.de>

Export the granularity that write streams should be discarded with,
as it is essential for making good use of them.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 Documentation/ABI/stable/sysfs-block | 8 ++++++++
 block/blk-sysfs.c                    | 3 +++
 include/linux/blkdev.h               | 7 +++++++
 3 files changed, 18 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index f67139b8b8eff..c454c68b68fe6 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -514,6 +514,14 @@ Description:
 		supported. If supported, valid values are 1 through
 		max_write_streams, inclusive.
 
+What:		/sys/block/<disk>/queue/write_stream_granularity
+Date:		November 2024
+Contact:	linux-block@vger.kernel.org
+Description:
+		[RO] Granularity of a write stream in bytes.  The granularity
+		of a write stream is the size that should be discarded or
+		overwritten together to avoid write amplification in the device.
+
 What:		/sys/block/<disk>/queue/max_segments
 Date:		March 2010
 Contact:	linux-block@vger.kernel.org
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index c514c0cb5e93c..525f4fa132cd3 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -105,6 +105,7 @@ QUEUE_SYSFS_LIMIT_SHOW(max_discard_segments)
 QUEUE_SYSFS_LIMIT_SHOW(max_integrity_segments)
 QUEUE_SYSFS_LIMIT_SHOW(max_segment_size)
 QUEUE_SYSFS_LIMIT_SHOW(max_write_streams)
+QUEUE_SYSFS_LIMIT_SHOW(write_stream_granularity)
 QUEUE_SYSFS_LIMIT_SHOW(logical_block_size)
 QUEUE_SYSFS_LIMIT_SHOW(physical_block_size)
 QUEUE_SYSFS_LIMIT_SHOW(chunk_sectors)
@@ -448,6 +449,7 @@ QUEUE_RO_ENTRY(queue_max_segments, "max_segments");
 QUEUE_RO_ENTRY(queue_max_integrity_segments, "max_integrity_segments");
 QUEUE_RO_ENTRY(queue_max_segment_size, "max_segment_size");
 QUEUE_RO_ENTRY(queue_max_write_streams, "max_write_streams");
+QUEUE_RO_ENTRY(queue_write_stream_granularity, "write_stream_granularity");
 QUEUE_RW_LOAD_MODULE_ENTRY(elv_iosched, "scheduler");
 
 QUEUE_RO_ENTRY(queue_logical_block_size, "logical_block_size");
@@ -583,6 +585,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_max_integrity_segments_entry.attr,
 	&queue_max_segment_size_entry.attr,
 	&queue_max_write_streams_entry.attr,
+	&queue_write_stream_granularity_entry.attr,
 	&queue_hw_sector_size_entry.attr,
 	&queue_logical_block_size_entry.attr,
 	&queue_physical_block_size_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ce2c3ddda2411..7be8cc57561a1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -400,6 +400,7 @@ struct queue_limits {
 	unsigned short		max_discard_segments;
 
 	unsigned short		max_write_streams;
+	unsigned int		write_stream_granularity;
 
 	unsigned int		max_open_zones;
 	unsigned int		max_active_zones;
@@ -1249,6 +1250,12 @@ static inline unsigned short bdev_max_write_streams(struct block_device *bdev)
 	return bdev_limits(bdev)->max_write_streams;
 }
 
+static inline unsigned int
+bdev_write_stream_granularity(struct block_device *bdev)
+{
+	return bdev_limits(bdev)->write_stream_granularity;
+}
+
 static inline unsigned queue_logical_block_size(const struct request_queue *q)
 {
 	return q->limits.logical_block_size;
-- 
2.43.5