On Tue, Aug 16, 2022 at 09:27:56AM -0400, Jeff Layton wrote:
> From: Jeff Layton <jlayton@xxxxxxxxxx>
>
> Claim one of the spare fields in struct statx to hold a 64-bit change
> attribute. When statx requests this attribute, do an
> inode_query_iversion and fill the result in the field.
>
> Also update the test-statx.c program to display the change attribute and
> the mountid as well.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/stat.c | 7 +++++++
> include/linux/stat.h | 1 +
> include/uapi/linux/stat.h | 3 ++-
> samples/vfs/test-statx.c | 8 ++++++--
> 4 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/fs/stat.c b/fs/stat.c
> index 9ced8860e0f3..7c3d063c31ba 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -17,6 +17,7 @@
> #include <linux/syscalls.h>
> #include <linux/pagemap.h>
> #include <linux/compat.h>
> +#include <linux/iversion.h>
>
> #include <linux/uaccess.h>
> #include <asm/unistd.h>
> @@ -118,6 +119,11 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
> stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
> STATX_ATTR_DAX);
>
> + if ((request_mask & STATX_CHANGE_ATTR) && IS_I_VERSION(inode)) {
> + stat->result_mask |= STATX_CHANGE_ATTR;
> + stat->change_attr = inode_query_iversion(inode);
> + }
> +
> mnt_userns = mnt_user_ns(path->mnt);
> if (inode->i_op->getattr)
> return inode->i_op->getattr(mnt_userns, path, stat,
> @@ -611,6 +617,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
> tmp.stx_dev_major = MAJOR(stat->dev);
> tmp.stx_dev_minor = MINOR(stat->dev);
> tmp.stx_mnt_id = stat->mnt_id;
> + tmp.stx_change_attr = stat->change_attr;
>
> return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
> }
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 7df06931f25d..7b444c2ad0ad 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -50,6 +50,7 @@ struct kstat {
> struct timespec64 btime; /* File creation time */
> u64 blocks;
> u64 mnt_id;
> + u64 change_attr;
> };
>
> #endif
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 1500a0f58041..fd839ec76aa4 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -124,7 +124,7 @@ struct statx {
> __u32 stx_dev_minor;
> /* 0x90 */
> __u64 stx_mnt_id;
> - __u64 __spare2;
> + __u64 stx_change_attr; /* Inode change attribute */
> /* 0xa0 */
> __u64 __spare3[12]; /* Spare space for future expansion */
> /* 0x100 */
> @@ -152,6 +152,7 @@ struct statx {
> #define STATX_BASIC_STATS 0x000007ffU /* The stuff in the normal stat struct */
> #define STATX_BTIME 0x00000800U /* Want/got stx_btime */
> #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */
> +#define STATX_CHANGE_ATTR 0x00002000U /* Want/got stx_change_attr */
I'm a bit worried that STATX_CHANGE_ATTR isn't a good name for the flag
and field. Or I fail to understand what exact information this will
expose and how userspace will consume it.
To me the naming gives the impression that some set of generic
attributes have changed but given that statx is about querying file
attributes this becomes confusing.
Wouldn't it make more sense this time to expose it as what it is and
call this STATX_INO_VERSION and __u64 stx_ino_version?
