Re: Why do we update ctime in generic_file_write?

[Andreas Dilger <adilger@clusterfs.com>]

On Jan 21, 2003  19:34 -0600, Steven French wrote:
> I saw the place in 2.4's generic_file_write in which
>        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
> but I didn't see such a line in 2.5.56 or 2.5.58
> Are you seeing it set somewhere else, less obvious, in this path?

In 2.4, generic_file_write() calls update_inode_times(inode) which
updates both mtime and ctime if they are at least a second old.
In 2.5 it calls inode_update_time(inode, 1) which updates the mtime,
and the "1" indicates that the ctime should be updated (both are
updated only if the time is over a second old).

> The writeups I found on st_ctime would indicate that, as you noticed,
> it should not be set there - POSIX spec said:
>       "for changed file status, for example, chmod()"
> and the man page on fstat says:
>       "is changed by writing or setting inode information
>       (ie owner, group, link count, mode)"

Good.

> Andreas Dilger wrote:
> >I was looking at the code in generic file write (both 2.4 and 2.5) and in
> >both cases we update the ctime always.  My understanding here is that the
> >mtime reflects the data modification time, while the ctime reflects the
> >inode change time, so we should only be updating the ctime (at most) if
> >the file size was increased, and not if we are overwriting data.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/