We're planning to expose the inode change attribute via statx. Document
what this value means and what an observer can infer from a change in
its value.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
man2/statx.2 | 13 +++++++++++++
man7/inode.7 | 10 ++++++++++
2 files changed, 23 insertions(+)
diff --git a/man2/statx.2 b/man2/statx.2
index 0d1b4591f74c..644fb251f114 100644
--- a/man2/statx.2
+++ b/man2/statx.2
@@ -62,6 +62,7 @@ struct statx {
__u32 stx_dev_major; /* Major ID */
__u32 stx_dev_minor; /* Minor ID */
__u64 stx_mnt_id; /* Mount ID */
+ __u64 stx_ino_version; /* Inode change attribute */
};
.EE
.in
@@ -247,6 +248,7 @@ STATX_BTIME Want stx_btime
STATX_ALL The same as STATX_BASIC_STATS | STATX_BTIME.
It is deprecated and should not be used.
STATX_MNT_ID Want stx_mnt_id (since Linux 5.8)
+STATX_INO_VERSION Want stx_ino_version (since Linux 6.1)
.TE
.in
.PP
@@ -411,6 +413,17 @@ and corresponds to the number in the first field in one of the records in
For further information on the above fields, see
.BR inode (7).
.\"
+.TP
+.I stx_ino_version
+The inode version, also known as the inode change attribute. This
+value is intended to change any time there is an inode status change. Any
+operation that would cause the stx_ctime to change should also cause
+stx_ino_version to change, even when there is no apparent change to the
+stx_ctime due to timestamp granularity.
+.IP
+Note that an observer cannot infer anything about the nature or
+magnitude of the change from the value of this field. A change in this value
+only indicates that there may have been an explicit change in the inode.
.SS File attributes
The
.I stx_attributes
diff --git a/man7/inode.7 b/man7/inode.7
index 9b255a890720..d296bb6df70c 100644
--- a/man7/inode.7
+++ b/man7/inode.7
@@ -184,6 +184,16 @@ Last status change timestamp (ctime)
This is the file's last status change timestamp.
It is changed by writing or by setting inode information
(i.e., owner, group, link count, mode, etc.).
+.TP
+Inode version (i_version)
+(not returned in the \fIstat\fP structure); \fIstatx.stx_ino_version\fP
+.IP
+This is the inode change attribute. Any operation that would result in a ctime
+change should also result in a change to this value. The value must change even
+in the case where the ctime change is not evident due to timestamp granularity.
+An observer cannot infer anything from the actual value about the nature or
+magnitude of the change. If it is different from the last time it was checked,
+then something may have made an explicit change to the inode.
.PP
The timestamp fields report time measured with a zero point at the
.IR Epoch ,
--
2.37.2
