Re: [PATCH v6 2/4] populate: add ability to populate a filesystem from a directory

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Apr 25, 2025 at 06:10:14AM -0700, Christoph Hellwig wrote:
> On Thu, Apr 24, 2025 at 03:00:41PM -0700, Darrick J. Wong wrote:
> > The thing is, if you were relying on atime/mtime for detection of "file
> > data changed since last read" then /not/ copying atime into the
> > filesystem breaks that property in the image.
> 
> I don't think that matter for images, because no software will keep
> running over the upgrade of the image.  Also plenty of people run
> with noatime, and btrfs even defaulted to it for a while (not sure if
> it still does).
> 
> At the same time having the same behavior as mkfs.ext4 is a good thing
> by itself because people obviously have been using it and consistency
> is always a good thing.

I don't see where mke2fs -d actually copies i_mtime into the filesystem.
In misc/create_inode.c I see a lot of:

	now = fs->now ? fs->now : time(0);
	ext2fs_inode_xtime_set(&inode, i_atime, now);
	ext2fs_inode_xtime_set(&inode, i_ctime, now);
	ext2fs_inode_xtime_set(&inode, i_mtime, now);

which implies that all three are set to a predetermined timestamp or the
current timestamp.

Also while I'm scanning create_inode.c, do you want to preserve
hardlinks?

> > How about copying [acm]time from the source file by default, but then
> > add a new -p noatime option to skip the atime?
> 
> I'd probably invert the polarity.  When building an image keeping
> atime especially and also ctime is usually not very useful.  But that
> would give folks who need it for some reason a way to do so.

Either's fine with me.

--D