[PATCH RESEND] ubifs: Introduce a mount option of force_atime.

[Artem Bityutskiy]

On Mon, 2015-06-08 at 18:07 +0800, Dongsheng Yang wrote:
> Currently, ubifs does not support access time anyway. I understand
> that there is a overhead to update inode in each access from user.
> 
> But for the following two reasons, I think we can make it optional
> to user.
> 
> (1). More and more flash storage in server are trying to use ubifs,
> it is not only for a device such as mobile phone any more, we want
> to use it in more and more generic way. Then we need to compete
> with some other main filesystems. From this point, access time is
> necessary to us, at least as a choice to user currently.
> 
> (2). The default mount option about atime is relatime currently,
> it's much relaxy compared with strictatime. Then we don't update
> the inode in any accessing. So the overhead is not too much.
> It's really acceptable.
> 
> Signed-off-by: Dongsheng Yang <yangds.fnst at cn.fujitsu.com>
> ---
> 	It's a RESEND patch to cc to fsdevel as Artem suggested.
> I would rename force_atime to enable_atime in next version.

Why do you need to introduce a custom "force_atime" option if there are
already standard "atime" and "noatime" mount option? I am fine with
adding atime support to UBIFS in general, and I'd expect this behavior
then.

1. mount -t ubifs ... - no atime by default
2. mount -t ubifs -o noatime ... - same as above
3. mount -t ubifs -o atime - support atime
4. mount -t ubifs -o rlatime - support relatime

and so on for as many atime update strategies you want to support.