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From: Jeff Layton <>
	Colin Walters <>
Subject: [PATCH v4 1/6] iversion: update comments with info about atime updates
Date: Wed,  7 Sep 2022 07:33:13 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

The i_version field in the kernel has had different semantics over
the decades, but we're now proposing to expose it to userland via
statx. This means that we need a clear, consistent definition of
what it means and when it should change.

Update the comments in iversion.h to describe when the i_version
must change.

Cc: Colin Walters <>
Cc: NeilBrown <>
Cc: Trond Myklebust <>
Cc: Dave Chinner <>
Signed-off-by: Jeff Layton <>
 include/linux/iversion.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/iversion.h b/include/linux/iversion.h
index 3bfebde5a1a6..0555a3851dbf 100644
--- a/include/linux/iversion.h
+++ b/include/linux/iversion.h
@@ -9,8 +9,14 @@
  * ---------------------------
  * The change attribute (i_version) is mandated by NFSv4 and is mostly for
  * knfsd, but is also used for other purposes (e.g. IMA). The i_version must
- * appear different to observers if there was a change to the inode's data or
- * metadata since it was last queried.
+ * appear larger to observers if there was an explicit change to the inode's
+ * data or metadata since it was last queried.
+ *
+ * An explicit change is one that would ordinarily result in a change to the
+ * inode status change time (aka ctime). i_version must appear to change, even
+ * if the ctime does not (since the whole point is to avoid missing updates due
+ * to timestamp granularity). If POSIX mandates that the ctime must change due
+ * to an operation, then the i_version counter must be incremented as well.
  * Observers see the i_version as a 64-bit number that never decreases. If it
  * remains the same since it was last checked, then nothing has changed in the

  reply	other threads:[~2022-09-07 11:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-07 11:33 [PATCH v4 0/6] vfs: clean up i_version behavior and expose it via statx Jeff Layton
2022-09-07 11:33 ` Jeff Layton [this message]
2022-09-07 11:33 ` [PATCH v4 2/6] ext4: fix i_version handling in ext4 Jeff Layton
2022-09-07 11:33 ` [PATCH v4 3/6] ext4: unconditionally enable the i_version counter Jeff Layton
2022-09-07 11:33 ` [PATCH v4 4/6] vfs: report an inode version in statx for IS_I_VERSION inodes Jeff Layton
2022-09-07 11:33 ` [PATCH v4 5/6] nfs: report the inode version in statx if requested Jeff Layton
2022-09-07 11:33 ` [PATCH v4 6/6] ceph: fill in the change attribute in statx requests Jeff Layton

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