Re: [PATCH 5/6] fuse: truncate file if async dio failed

[Maxim V. Patlasov]

12/17/2012 11:04 PM, Brian Foster ÐÐÑÐÑ:
> On 12/17/2012 09:13 AM, Maxim V. Patlasov wrote:
> > Hi,
> >
> > 12/15/2012 12:16 AM, Brian Foster ÐÐÑÐÑ:
> > > On 12/14/2012 10:21 AM, Maxim V. Patlasov wrote:
> ...
> > > > +
> > > fuse_do_truncate() looks fairly close to fuse_do_setattr(). Is there any
> > > reason we couldn't make fuse_do_setattr() non-static, change the dentry
> > > parameter to an inode and use that?
> > fuse_do_setattr() performs extra checks that fuse_do_truncate() needn't.
> > Some of them are harmless, some not: fuse_allow_task() may return 0 if
> > task credentials changed. E.g. super-user successfully opened a file,
> > then setuid(other_user_uid), then write(2) to the file. write(2) doesn't
> > check uid, but fuse_do_truncate() - via fuse_allow_task() - does.
> Conversely, what about the extra error handling bits in
> fuse_do_setattr() that do not appear in fuse_do_truncate() (i.e., the
> inode mode check, the change attributes call, updating the inode size,
> etc.)? It seems like we would want some of that code here.

Yes, they won't harm.

> fuse_setattr() is the only caller of fuse_do_setattr(), so why not embed
> some of the initial checks (such as fuse_allow_task()) there? I suppose
> we could pull out some of the error handling checks there as well if
> they are considered harmful to this post-write error truncate situation.

Makes sense. I like it especially because it allows to avoid code 
duplication (handling FUSE_SETATTR fuse-request).

> FWIW, I just tested a quick change that pulls up the fuse_allow_task()
> check (via instrumenting a write error) and it seems to work as
> expected. I can forward a patch if interested...

I did exactly the same before sending previous email :) In my tests it 
works as expected too (modulo fuse_allow_task() that we can move up). 
I'll re-send corrected patch soon.

Thanks,
Maxim
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