[PATCHv10 7/9] block: export placement hint feature

[Keith Busch <kbusch@xxxxxxxx>]

From: Keith Busch <kbusch@xxxxxxxxxx>

Add a feature flag for devices that support generic placement hints in
write commands. This is in contrast to data lifetime hints.

Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
---
 block/blk-settings.c   | 2 ++
 block/blk-sysfs.c      | 3 +++
 include/linux/blkdev.h | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 921fb4d334fa4..7e3bb3cec7032 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -518,6 +518,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 		t->features &= ~BLK_FEAT_NOWAIT;
 	if (!(b->features & BLK_FEAT_POLL))
 		t->features &= ~BLK_FEAT_POLL;
+	if (!(b->features & BLK_FEAT_PLACEMENT_HINTS))
+		t->features &= ~BLK_FEAT_PLACEMENT_HINTS;
 
 	t->flags |= (b->flags & BLK_FLAG_MISALIGNED);
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 85f48ca461049..51e0b99c2210a 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -260,6 +260,7 @@ static ssize_t queue_##_name##_show(struct gendisk *disk, char *page)	\
 QUEUE_SYSFS_FEATURE_SHOW(poll, BLK_FEAT_POLL);
 QUEUE_SYSFS_FEATURE_SHOW(fua, BLK_FEAT_FUA);
 QUEUE_SYSFS_FEATURE_SHOW(dax, BLK_FEAT_DAX);
+QUEUE_SYSFS_FEATURE_SHOW(placement_hints, BLK_FEAT_PLACEMENT_HINTS);
 
 static ssize_t queue_zoned_show(struct gendisk *disk, char *page)
 {
@@ -497,6 +498,7 @@ QUEUE_RW_ENTRY(queue_poll_delay, "io_poll_delay");
 QUEUE_RW_ENTRY(queue_wc, "write_cache");
 QUEUE_RO_ENTRY(queue_fua, "fua");
 QUEUE_RO_ENTRY(queue_dax, "dax");
+QUEUE_RO_ENTRY(queue_placement_hints, "placement_hints");
 QUEUE_RW_ENTRY(queue_io_timeout, "io_timeout");
 QUEUE_RO_ENTRY(queue_virt_boundary_mask, "virt_boundary_mask");
 QUEUE_RO_ENTRY(queue_dma_alignment, "dma_alignment");
@@ -626,6 +628,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_wc_entry.attr,
 	&queue_fua_entry.attr,
 	&queue_dax_entry.attr,
+	&queue_placement_hints_entry.attr,
 	&queue_poll_delay_entry.attr,
 	&queue_virt_boundary_mask_entry.attr,
 	&queue_dma_alignment_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 90a19ea889276..c577a607591de 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -333,6 +333,9 @@ typedef unsigned int __bitwise blk_features_t;
 #define BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE \
 	((__force blk_features_t)(1u << 15))
 
+/* supports generic write placement hints */
+#define BLK_FEAT_PLACEMENT_HINTS	((__force blk_features_t)(1u << 16))
+
 /*
  * Flags automatically inherited when stacking limits.
  */
-- 
2.43.5