Re: [PATCH] iversion: update comments with info about atime updates

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Aug 24, 2022 at 08:24:47AM +1000, NeilBrown wrote:
> On Tue, 23 Aug 2022, Jeff Layton wrote:
> > On Tue, 2022-08-23 at 21:38 +1000, NeilBrown wrote:
> > > On Tue, 23 Aug 2022, Jeff Layton wrote:
> > > > So, we can refer to that and simply say:
> > > > 
> > > > "If the function updates the mtime or ctime on the inode, then the
> > > > i_version should be incremented. If only the atime is being updated,
> > > > then the i_version should not be incremented. The exception to this rule
> > > > is explicit atime updates via utimes() or similar mechanism, which
> > > > should result in the i_version being incremented."
> > > 
> > > Is that exception needed?  utimes() updates ctime.
> > > 
> > > https://man7.org/linux/man-pages/man2/utimes.2.html
> > > 
> > > doesn't say that, but
> > > 
> > > https://pubs.opengroup.org/onlinepubs/007904875/functions/utimes.html
> > > 
> > > does, as does the code.
> > > 
> > 
> > Oh, good point! I think we can leave that out. Even better!
> 
> Further, implicit mtime updates (file_update_time()) also update ctime.
> So all you need is
>    If the function updates the ctime, then i_version should be
>    incremented.
> 
> and I have to ask - why not just use the ctime?  Why have another number
> that is parallel?
> 
> Timestamps are updated at HZ (ktime_get_course) which is at most every
> millisecond.

Kernel time, and therefore timestamps, can go backwards.

-Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux