[PATCH 5.9 45/46] uapi: fix statx attribute value overlap for DAX & MOUNT_ROOT

[Greg Kroah-Hartman]

From: Eric Sandeen <sandeen@xxxxxxxxxx>

commit 72d1249e2ffdbc344e465031ec5335fa3489d62e upstream.

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.

Fixes: 80340fe3605c ("statx: add mount_root")
Fixes: 712b2698e4c0 ("fs/stat: Define DAX statx attribute")
Link: https://lore.kernel.org/linux-fsdevel/7027520f-7c79-087e-1d00-743bdefa1a1e@xxxxxxxxxx/
Link: https://lore.kernel.org/lkml/20201202214629.1563760-1-ira.weiny@xxxxxxxxx/
Reported-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Reviewed-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.8
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/uapi/linux/stat.h |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -171,9 +171,12 @@ 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 file is in the CPU
+ * direct access state.  It does not correspond to the per-inode flag that
+ * some filesystems support.
+ *
  */
 #define STATX_ATTR_COMPRESSED		0x00000004 /* [I] File is compressed by the fs */
 #define STATX_ATTR_IMMUTABLE		0x00000010 /* [I] File is marked immutable */
@@ -183,7 +186,7 @@ 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			0x00200000 /* File is currently in DAX state */
 
 
 #endif /* _UAPI_LINUX_STAT_H */