Add an explicit paragraph codifying that atime updates due to reads should not be counted against the i_version counter. None of the existing subsystems that use the i_version want those counted, and there is an easy workaround for those that do. Cc: NeilBrown <neilb@xxxxxxx> Cc: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Link: https://lore.kernel.org/linux-xfs/166086932784.5425.17134712694961326033@xxxxxxxxxxxxxxxxxxxxx/#t Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> --- 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..da6cc1cc520a 100644 --- a/include/linux/iversion.h +++ b/include/linux/iversion.h @@ -9,8 +9,8 @@ * --------------------------- * 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 different to observers if there was an explicit change to the inode's + * data or metadata since it was last queried. * * 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 @@ -18,6 +18,12 @@ * anything about the nature or magnitude of the changes from the value, only * that the inode has changed in some fashion. * + * Note that atime updates due to reads or similar activity do _not_ represent + * an explicit change to the inode. If the only change is to the atime and it + * wasn't set via utimes() or a similar mechanism, then i_version should not be + * incremented. If an observer cares about atime updates, it should plan to + * fetch and store them in conjunction with the i_version. + * * Not all filesystems properly implement the i_version counter. Subsystems that * want to use i_version field on an inode should first check whether the * filesystem sets the SB_I_VERSION flag (usually via the IS_I_VERSION macro). -- 2.37.2
