[PATCH] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP

[PATCH] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP

[Jeff Layton]

Userland has no way to tell whether a file's timestamps are multigrain,
i.e. whether successive changes after a query are guaranteed to yield
distinct timestamps.

Add STATX_ATTR_MULTIGRAIN_TIMESTAMP and set it in vfs_getattr_nosec()
when is_mgtime() is true (IOP_MGTIME is set from FS_MGTIME at inode
init). Always advertise it in attributes_mask.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
HCH suggested this when I posted the fstest for multigrain timestamps. I
think it makes sense. If this looks good, I'll plan to send a manpage
update for statx(2).
---
 fs/stat.c                 | 6 +++++-
 include/uapi/linux/stat.h | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/stat.c b/fs/stat.c
index a2e63c6c45b7..67b9f1784b23 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -206,9 +206,13 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
 	if (IS_VERITY(inode))
 		stat->attributes |= STATX_ATTR_VERITY;
 
+	if (is_mgtime(inode))
+		stat->attributes |= STATX_ATTR_MULTIGRAIN_TIMESTAMP;
+
 	stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
 				  STATX_ATTR_DAX |
-				  STATX_ATTR_VERITY);
+				  STATX_ATTR_VERITY |
+				  STATX_ATTR_MULTIGRAIN_TIMESTAMP);
 
 	idmap = mnt_idmap(path->mnt);
 	if (inode->i_op->getattr) {
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 1686861aae20..b978860590b1 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -255,6 +255,7 @@ struct statx {
 #define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
 #define STATX_ATTR_DAX			0x00200000 /* File is currently in DAX state */
 #define STATX_ATTR_WRITE_ATOMIC		0x00400000 /* File supports atomic write operations */
+#define STATX_ATTR_MULTIGRAIN_TIMESTAMP	0x00800000 /* File uses multigrain timestamps */
 
 
 #endif /* _UAPI_LINUX_STAT_H */

---
base-commit: c339f4010dea8b0d754f84ace70cd1b089878ef8
change-id: 20261029-mgtime-statx-26a229f9c3b4

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP

[Jan Kara]

On Thu 29-10-26 12:28:16, Jeff Layton wrote:
> Userland has no way to tell whether a file's timestamps are multigrain,
> i.e. whether successive changes after a query are guaranteed to yield
> distinct timestamps.
> 
> Add STATX_ATTR_MULTIGRAIN_TIMESTAMP and set it in vfs_getattr_nosec()
> when is_mgtime() is true (IOP_MGTIME is set from FS_MGTIME at inode
> init). Always advertise it in attributes_mask.
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

Makes sense to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
> HCH suggested this when I posted the fstest for multigrain timestamps. I
> think it makes sense. If this looks good, I'll plan to send a manpage
> update for statx(2).
> ---
>  fs/stat.c                 | 6 +++++-
>  include/uapi/linux/stat.h | 1 +
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/stat.c b/fs/stat.c
> index a2e63c6c45b7..67b9f1784b23 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -206,9 +206,13 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
>  	if (IS_VERITY(inode))
>  		stat->attributes |= STATX_ATTR_VERITY;
>  
> +	if (is_mgtime(inode))
> +		stat->attributes |= STATX_ATTR_MULTIGRAIN_TIMESTAMP;
> +
>  	stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
>  				  STATX_ATTR_DAX |
> -				  STATX_ATTR_VERITY);
> +				  STATX_ATTR_VERITY |
> +				  STATX_ATTR_MULTIGRAIN_TIMESTAMP);
>  
>  	idmap = mnt_idmap(path->mnt);
>  	if (inode->i_op->getattr) {
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 1686861aae20..b978860590b1 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -255,6 +255,7 @@ struct statx {
>  #define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
>  #define STATX_ATTR_DAX			0x00200000 /* File is currently in DAX state */
>  #define STATX_ATTR_WRITE_ATOMIC		0x00400000 /* File supports atomic write operations */
> +#define STATX_ATTR_MULTIGRAIN_TIMESTAMP	0x00800000 /* File uses multigrain timestamps */
>  
>  
>  #endif /* _UAPI_LINUX_STAT_H */
> 
> ---
> base-commit: c339f4010dea8b0d754f84ace70cd1b089878ef8
> change-id: 20261029-mgtime-statx-26a229f9c3b4
> 
> Best regards,
> -- 
> Jeff Layton <jlayton@kernel.org>
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP

[Christian Brauner]

On Thu, 29 Oct 2026 12:28:16 -0400, Jeff Layton wrote:
> Userland has no way to tell whether a file's timestamps are multigrain,
> i.e. whether successive changes after a query are guaranteed to yield
> distinct timestamps.
> 
> Add STATX_ATTR_MULTIGRAIN_TIMESTAMP and set it in vfs_getattr_nosec()
> when is_mgtime() is true (IOP_MGTIME is set from FS_MGTIME at inode
> init). Always advertise it in attributes_mask.
> 
> [...]

Applied to the vfs-7.5.misc branch of the vfs/vfs.git tree.
Patches in the vfs-7.5.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-7.5.misc

[1/1] statx: add STATX_ATTR_MULTIGRAIN_TIMESTAMP
      https://git.kernel.org/vfs/vfs/c/81f2cc03b537