Re: [PATCH 1/2] uapi: fix statx attribute value overlap for DAX & MOUNT_ROOT

STATX_ATTR_MOUNT_ROOT and STATX_ATTR_DAX got merged with the same value,
so one of them needs fixing. Move STATX_ATTR_DAX.

While we're in here, clarify the value-matching scheme for some of the
attributes, and explain why the value for DAX does not match.

Signed-off-by: Eric Sandeen <redacted>
---
 include/uapi/linux/stat.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 82cc58fe9368..9ad19eb9bbbf 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h

@@ -171,9 +171,10 @@ struct statx {
  * be of use to ordinary userspace programs such as GUIs or ls rather than
  * specialised tools.
  *
- * Note that the flags marked [I] correspond to generic FS_IOC_FLAGS
+ * Note that the flags marked [I] correspond to the FS_IOC_SETFLAGS flags
  * semantically.  Where possible, the numerical value is picked to correspond
- * also.
+ * also. Note that the DAX attribute indicates that the inode is currently
+ * DAX-enabled, not simply that the per-inode flag has been set.
  */
 #define STATX_ATTR_COMPRESSED		0x00000004 /* [I] File is compressed by the fs */
 #define STATX_ATTR_IMMUTABLE		0x00000010 /* [I] File is marked immutable */

@@ -183,7 +184,7 @@ struct statx {
 #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
 #define STATX_ATTR_MOUNT_ROOT		0x00002000 /* Root of a mount */
 #define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
-#define STATX_ATTR_DAX			0x00002000 /* [I] File is DAX */
+#define STATX_ATTR_DAX			0x00400000 /* File is currently DAX-enabled */