# Re: \[PATCH RFC\] vfs: add a O\_NOMTIME flag

- List: linux-api
- 3 messages, 2 authors
- Page: https://ratatoskr.run/linux-api/2015/07/97594/t

## Re: \[PATCH RFC\] vfs: add a O\_NOMTIME flag

- From: Pavel Machek \<hidden\>
- Date: 2015-07-14 13:13:00 
- Message: https://ratatoskr.run/linux-api/2015/07/97594.md

```text
Hi!

> BTW When you "swap" to a file the mtime doesn't get updated.  No one seems to
> complain about that.  I guess it is a rather narrow use-case though.

Actually yes, I'd like to complain.

It was not swap, it was mount -o loop, but I guess that's the same
case. Then rsync refused to work on that file... and being on slow ARM
system it took me a while to figure out WTF is going on.

So yes, we have problems with mtime, and yes, they matter.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
```

## Re: \[PATCH RFC\] vfs: add a O\_NOMTIME flag

- From: NeilBrown \<hidden\>
- Date: 2015-07-15 04:54:56 
- Message: https://ratatoskr.run/linux-api/2015/07/97609.md

```text
On Tue, 14 Jul 2015 15:13:00 +0200 Pavel Machek [ref] wrote:

> Hi!
> 
> > BTW When you "swap" to a file the mtime doesn't get updated.  No one seems to
> > complain about that.  I guess it is a rather narrow use-case though.
> 
> Actually yes, I'd like to complain.
> 
> It was not swap, it was mount -o loop, but I guess that's the same
> case. Then rsync refused to work on that file... and being on slow ARM
> system it took me a while to figure out WTF is going on.
> 
> So yes, we have problems with mtime, and yes, they matter.
> 									Pavel

Odd...
I assume you mean
  mount -o loop /some/file  /mountpoint

and then when you write to the filesystem on /mountpoint the mtime
of /some/file doesn't get updated?
I think it should.
 drivers/block/loop.c uses vfs_iter_write() to write to a file.
 That calls f_op->write_iter which will typically call
 generic_file_write_iter() which will call file_update_time() to update
 the time stamps.

What filesystem was /some/file on?
I just did some testing on ext4 and it seems to do the right thing
mtime gets updated.

NeilBrown
```

## Re: \[PATCH RFC\] vfs: add a O\_NOMTIME flag

- From: Pavel Machek \<hidden\>
- Date: 2015-07-22 13:47:13 
- Message: https://ratatoskr.run/linux-api/2015/07/97890.md

```text
On Wed 2015-07-15 14:54:56, NeilBrown wrote:
> On Tue, 14 Jul 2015 15:13:00 +0200 Pavel Machek [ref] wrote:
> 
> > Hi!
> > 
> > > BTW When you "swap" to a file the mtime doesn't get updated.  No one seems to
> > > complain about that.  I guess it is a rather narrow use-case though.
> > 
> > Actually yes, I'd like to complain.
> > 
> > It was not swap, it was mount -o loop, but I guess that's the same
> > case. Then rsync refused to work on that file... and being on slow ARM
> > system it took me a while to figure out WTF is going on.
> > 
> > So yes, we have problems with mtime, and yes, they matter.
> > 									Pavel
> 
> Odd...
> I assume you mean
>   mount -o loop /some/file  /mountpoint
> 
> and then when you write to the filesystem on /mountpoint the mtime
> of /some/file doesn't get updated?
> I think it should.
>  drivers/block/loop.c uses vfs_iter_write() to write to a file.
>  That calls f_op->write_iter which will typically call
>  generic_file_write_iter() which will call file_update_time() to update
>  the time stamps.

Yes, that. I'm pretty sure I seen it, but it was probably on 2.6.X
kernel... Does it make sense to try to reproduce it on the old kernel?

> What filesystem was /some/file on?

Very probably VFAT.

> I just did some testing on ext4 and it seems to do the right thing
> mtime gets updated.

Yes, I tried here, and it seems to be ok.

Thanks,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
```