[linux-cifs-client] Re: set last write time = fsync ?
Steve French
smfrench at gmail.com
Fri Mar 14 21:38:27 GMT 2008
On Fri, Mar 14, 2008 at 3:35 PM, Jeff Layton <jlayton at redhat.com> wrote:
> On Fri, 14 Mar 2008 14:19:06 -0500
>
> "Steve French" <smfrench at gmail.com> wrote:
>
> > On Fri, Mar 14, 2008 at 11:55 AM, Jeff Layton <jlayton at redhat.com> wrote:
> > > On Fri, 14 Mar 2008 11:16:41 -0500
> > >
> > > "Steve French" <smfrench at gmail.com> wrote:
> > >
> > >
> > > > I don't worry about flushing atime (anyone crazy enough to do that
> > > > would pay a huge performance penalty).
> > > > Access is usually checked on open right ... so once a file is open
> > > > even if the file becomes read-only, the writes, even cached writes
> > > > continue.
> > > >
> > >
> > > Ahh, you're correct. I've been doing a lot of NFS work lately and was
> > > thinking stateless... :-)
> > >
> > > That patch should be OK then, though I think if someone is purposefully
> > > setting the atime we should take care not to clobber it. We're not
> > > going to be going through this codepath on every atime update, are we?
> > > Just on utimes() type calls, correct? If so, doing a flush on atime
> > > updates might be reasonable as well...
> > >
> > > Jeff Layton <jlayton at redhat.com>
> > >
> >
> > I don't think we need to flush before setting (just) atime.
> > If the problem with timestamps is delayed writes getting written out
> > on close ... won't close update the atime anyway?
> >
> >
> Consider that an app like tar might do something like this:
>
> open()
> write()
> write()
> write()
> close()
> utimes()
>
> The app would likely set the mtime too, but I'm not sure we should make
> that assumption. The question is -- should we allow that utimes() call
> to be clobbered by writes lingering around after the close() returns?
There can't be writes lingering around after the close ... filp_close does
a flush before calling fput.
--
Thanks,
Steve
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