[PATCHv10 3/9] statx: add write hint information

[Keith Busch]

From: Keith Busch <kbusch at kernel.org>

If requested on a raw block device, report the maximum write hint the
block device supports.

Signed-off-by: Keith Busch <kbusch at kernel.org>
---
 block/bdev.c              | 5 +++++
 fs/stat.c                 | 1 +
 include/linux/stat.h      | 1 +
 include/uapi/linux/stat.h | 3 ++-
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/block/bdev.c b/block/bdev.c
index 738e3c8457e7f..9a59f0c882170 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -1296,6 +1296,11 @@ void bdev_statx(struct path *path, struct kstat *stat,
 		stat->result_mask |= STATX_DIOALIGN;
 	}
 
+	if (request_mask & STATX_WRITE_HINT) {
+		stat->write_hint_max = bdev_max_write_hints(bdev);
+		stat->result_mask |= STATX_WRITE_HINT;
+	}
+
 	if (request_mask & STATX_WRITE_ATOMIC && bdev_can_atomic_write(bdev)) {
 		struct request_queue *bd_queue = bdev->bd_queue;
 
diff --git a/fs/stat.c b/fs/stat.c
index 41e598376d7e3..60bcd5c2e2a1d 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -704,6 +704,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
 	tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min;
 	tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max;
 	tmp.stx_atomic_write_segments_max = stat->atomic_write_segments_max;
+	tmp.stx_write_hint_max = stat->write_hint_max;
 
 	return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
 }
diff --git a/include/linux/stat.h b/include/linux/stat.h
index 3d900c86981c5..48f0f64846a02 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -57,6 +57,7 @@ struct kstat {
 	u32		atomic_write_unit_min;
 	u32		atomic_write_unit_max;
 	u32		atomic_write_segments_max;
+	u32		write_hint_max;
 };
 
 /* These definitions are internal to the kernel for now. Mainly used by nfsd. */
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 887a252864416..10f5622c21113 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -132,7 +132,7 @@ struct statx {
 	__u32	stx_atomic_write_unit_max;	/* Max atomic write unit in bytes */
 	/* 0xb0 */
 	__u32   stx_atomic_write_segments_max;	/* Max atomic write segment count */
-	__u32   __spare1[1];
+	__u32   stx_write_hint_max;
 	/* 0xb8 */
 	__u64	__spare3[9];	/* Spare space for future expansion */
 	/* 0x100 */
@@ -164,6 +164,7 @@ struct statx {
 #define STATX_MNT_ID_UNIQUE	0x00004000U	/* Want/got extended stx_mount_id */
 #define STATX_SUBVOL		0x00008000U	/* Want/got stx_subvol */
 #define STATX_WRITE_ATOMIC	0x00010000U	/* Want/got atomic_write_* fields */
+#define STATX_WRITE_HINT	0x00020000U	/* Want/got write_hint_max */
 
 #define STATX__RESERVED		0x80000000U	/* Reserved for future struct statx expansion */
 
-- 
2.43.5