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From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Jamie Lokier <jamie@shareable.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: statfs() / statvfs() syscall ballsup...
Date: Fri, 10 Oct 2003 09:46:19 -0400	[thread overview]
Message-ID: <16262.47147.943477.24070@charged.uio.no> (raw)
In-Reply-To: <20031010123732.GA28224@mail.shareable.org>

>>>>> " " == Jamie Lokier <jamie@shareable.org> writes:

     > Trond Myklebust wrote:
    >> Belongs in fcntl()... Just return ENOLCK if someone tries to
    >> set a lease or a directory notification on an NFS file...

     > It should be a filesystem hook, so that even remote filesystems
     > like SMB can implement it, although it must be understood that
     > remote notification has different ordering properties than
     > local.

Sure. We might even try actually implementing leases on NFSv4 for
delegated files.

     > I don't care about the cache semantics at all; what I care
     > about is whether a returned stat() result may be stale.

Note that this too may be a per-file property. Under NFSv4 I can
guarantee you that stat() results are correct in the case where I have
a delegation. Otherwise, you are indeed subject to inherent races.
"noac" cannot entirely resolve such races, but it sounds as if it
could in the particular cases you describe.

     > This is not ideal.  In particular, I don't know of any way to
     > _guarantee_ that I have the latest file contents from remote
     > filesystems short of F_SETLK, which way too heavy.[2]

Err... open() should normally suffice to do that...

Unless you are simultaneously writing to the file on a remote system,
in which case you really need mandatory locking rather than NFSv2/v3's
weaker advisory model. Or possibly something like CIFS/SMB's open
"share" model (which can also be implemented in NFSv4).



...so I would argue that the caching models both can and do make a
difference to your example cases (contrary to what you assert).

Cheers,
  Trond

  reply	other threads:[~2003-10-10 13:46 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-10-09 22:16 Trond Myklebust
2003-10-09 22:26 ` Linus Torvalds
2003-10-09 23:19   ` Ulrich Drepper
2003-10-10  0:22     ` viro
2003-10-10  4:49       ` Jamie Lokier
2003-10-10  5:26         ` Trond Myklebust
2003-10-10 12:37           ` Jamie Lokier
2003-10-10 13:46             ` Trond Myklebust [this message]
2003-10-10 14:35               ` Jamie Lokier
2003-10-10 15:32                 ` Misc NFSv4 (was Re: statfs() / statvfs() syscall ballsup...) Trond Myklebust
2003-10-10 15:53                   ` Jamie Lokier
2003-10-10 16:07                     ` Trond Myklebust
2003-10-10 15:55                   ` Michael Shuey
2003-10-10 16:20                     ` Trond Myklebust
2003-10-10 16:45                     ` J. Bruce Fields
2003-10-10 14:39               ` statfs() / statvfs() syscall ballsup Jamie Lokier
2003-10-09 23:31   ` Trond Myklebust
2003-10-10 12:27   ` Joel Becker
2003-10-10 14:59     ` Linus Torvalds
2003-10-10 15:27       ` Joel Becker
2003-10-10 16:00         ` Linus Torvalds
2003-10-10 16:26           ` Joel Becker
2003-10-10 16:50             ` Linus Torvalds
2003-10-10 17:33               ` Joel Becker
2003-10-10 17:51                 ` Linus Torvalds
2003-10-10 18:13                   ` Joel Becker
2003-10-10 16:27           ` Valdis.Kletnieks
2003-10-10 16:33           ` Chris Friesen
2003-10-10 17:04             ` Linus Torvalds
2003-10-10 17:07               ` Linus Torvalds
2003-10-10 17:21                 ` Joel Becker
2003-10-10 16:01         ` Jamie Lokier
2003-10-10 16:33           ` Joel Becker
2003-10-10 16:58             ` Chris Friesen
2003-10-10 17:05               ` Trond Myklebust
2003-10-10 17:20               ` Joel Becker
2003-10-10 17:33                 ` Chris Friesen
2003-10-10 17:40                 ` Linus Torvalds
2003-10-10 17:54                   ` Trond Myklebust
2003-10-10 18:05                     ` Linus Torvalds
2003-10-10 20:40                       ` Trond Myklebust
2003-10-10 21:09                         ` Linus Torvalds
2003-10-10 22:17                           ` Trond Myklebust
2003-10-11  2:53                     ` Andrew Morton
2003-10-11  3:47                       ` Trond Myklebust
2003-10-10 18:05                   ` Joel Becker
2003-10-10 18:31                     ` Andrea Arcangeli
2003-10-10 20:33                     ` Helge Hafting
2003-10-10 20:07             ` Jamie Lokier
2003-10-12 15:31             ` Greg Stark
2003-10-12 16:13               ` Linus Torvalds
2003-10-12 22:09                 ` Greg Stark
2003-10-13  8:45                   ` Helge Hafting
2003-10-15 13:25                     ` Ingo Oeser
2003-10-15 15:03                       ` Greg Stark
2003-10-15 18:37                         ` Helge Hafting
2003-10-16 10:29                         ` Ingo Oeser
2003-10-16 14:02                           ` Greg Stark
2003-10-21 11:47                             ` Ingo Oeser
2003-10-10 18:20           ` Andrea Arcangeli
2003-10-10 18:36             ` Linus Torvalds
2003-10-10 19:03               ` Andrea Arcangeli
2003-10-09 23:16 ` Andreas Dilger
2003-10-09 23:24   ` Linus Torvalds

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