[PATCH V2] uapi: fix statx attribute value overlap for DAX & MOUNT_ROOT

Eric Sandeen
2020-12-01T23:23:37Z

[*] Note: This needs to be merged as soon as possible as it's introducing an incompatible UAPI change...

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")
Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: David Howells <dhowells@redhat.com>
---
V2: Change flag value per Darrick Wong
Tweak comment per Darrick Wong
Add Fixes: tags & reported-by & RVB per dhowells

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

diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 82cc58fe9368..1500a0f58041 100644
--- 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 */
--
2.17.0