[PATCHv4 3/9] block: export dma_alignment attribute

Keith Busch
2022-05-26T01:08:42Z

From: Keith Busch <kbusch@kernel.org>

User space may want to know how to align their buffers to avoid
bouncing. Export the queue attribute.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
Documentation/ABI/stable/sysfs-block | 9 +++++++++
block/blk-sysfs.c | 7 +++++++
2 files changed, 16 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index e8797cd09aff..08f6d00df138 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/dma_alignment
+Date: May 2022
+Contact: linux-block@vger.kernel.org
+Description:
+ Reports the alignment that user space addresses must have to be
+ used for raw block device access with O_DIRECT and other driver
+ specific passthrough mechanisms.
+
+
What: /sys/block/<disk>/queue/chunk_sectors
Date: September 2016
Contact: Hannes Reinecke <hare@suse.com>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 88bd41d4cb59..14607565d781 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -274,6 +274,11 @@ static ssize_t queue_virt_boundary_mask_show(struct request_queue *q, char *page
return queue_var_show(q->limits.virt_boundary_mask, page);
}

+static ssize_t queue_dma_alignment_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(queue_dma_alignment(q), page);
+}
+
#define QUEUE_SYSFS_BIT_FNS(name, flag, neg) \
static ssize_t \
queue_##name##_show(struct request_queue *q, char *page) \
@@ -606,6 +611,7 @@ QUEUE_RO_ENTRY(queue_dax, "dax");
QUEUE_RW_ENTRY(queue_io_timeout, "io_timeout");
QUEUE_RW_ENTRY(queue_wb_lat, "wbt_lat_usec");
QUEUE_RO_ENTRY(queue_virt_boundary_mask, "virt_boundary_mask");
+QUEUE_RO_ENTRY(queue_dma_alignment, "dma_alignment");

#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
QUEUE_RW_ENTRY(blk_throtl_sample_time, "throttle_sample_time");
@@ -667,6 +673,7 @@ static struct attribute *queue_attrs[] = {
&blk_throtl_sample_time_entry.attr,
#endif
&queue_virt_boundary_mask_entry.attr,
+ &queue_dma_alignment_entry.attr,
NULL,
};

--
2.30.2