[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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