From: Jeff Layton <jlayton@poochiereds.net>
To: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Benjamin Coddington <bcodding@redhat.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 0/3] Include OFD lock owners when looking up state
Date: Fri, 1 Apr 2016 12:19:24 -0400 [thread overview]
Message-ID: <20160401121924.70569ef2@synchrony.poochiereds.net> (raw)
In-Reply-To: <CAHQdGtQKqs--JP6-OT6jjNh6JXTG6+cebL64t8OW8q771UL8FQ@mail.gmail.com>
On Fri, 1 Apr 2016 12:09:31 -0400
Trond Myklebust <trond.myklebust@primarydata.com> wrote:
> On Fri, Apr 1, 2016 at 11:48 AM, Benjamin Coddington
> <bcodding@redhat.com> wrote:
> > On Fri, 1 Apr 2016, Trond Myklebust wrote:
> >
> >> On Fri, Apr 1, 2016 at 11:34 AM, Benjamin Coddington
> >> <bcodding@redhat.com> wrote:
> >> > The client sends IO only under the open stateid when using OFD (and flock)
> >> > locking instead of the appropriate lock stateid because the nfs_lock_context
> >> > only tracks POSIX lockowners, which is the reference to the process' file
> >> > table.
> >> >
> >> > This is a problem for two reasons. The first is that rfc7530,
> >> > section-9.1.4.5 states that IO sent by an entity corresponding to the
> >> > lock-owner which holds a byte-range lock should be sent under the lock
> >> > stateid for that lock. Otherwise, a server enforcing mandatory byte-range
> >> > locking might reject that operation. Secondly, not tracking OFD lock owners
> >> > means that accounting for IO sent under those owners is broken. That
> >> > creates a problem for some work to guarantee an unlock will be sent after
> >> > operations scheduled under a lock complete.
> >>
> >> OK. Can we just kill this in the bud? No support for OFD locks in NFS:
> >> this is nuts....
> >
> > Will you explain why it is nuts? That would be helpful for me.
>
> The point of the OFD crap was that they should work exactly like POSIX
> locks except for the unlock-on-close, the latter being managed by the
> VFS layer. If we have to make loads of changes to NFS in order to
> change the tracking of lock owners, then the design itself is broken,
> and needs to be fixed.
No, there were other reasons for them as well.
For instance, traditional POSIX locks are useless for serializing
betwee threads within the same process because the lock owner is always
the same regardless of which thread you're using. With OFD locks, this
is possible if each thread has its own file description.
--
Jeff Layton <jlayton@poochiereds.net>
next prev parent reply other threads:[~2016-04-01 16:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 15:34 [PATCH 0/3] Include OFD lock owners when looking up state Benjamin Coddington
2016-04-01 15:34 ` [PATCH 1/3] NFS: add get_nfs_lock_context, find_nfs_lock_context Benjamin Coddington
2016-04-01 16:45 ` kbuild test robot
2016-04-01 17:03 ` kbuild test robot
2016-04-01 15:34 ` [PATCH 2/3] NFS: add OFD lock owners to nfs_lock_context Benjamin Coddington
2016-04-01 16:17 ` kbuild test robot
2016-04-01 16:55 ` kbuild test robot
2016-04-01 15:34 ` [PATCH 3/3] NFSv4: use OFD lock owners in lock state lookup Benjamin Coddington
2016-04-01 15:47 ` [PATCH 0/3] Include OFD lock owners when looking up state Trond Myklebust
2016-04-01 15:48 ` Benjamin Coddington
2016-04-01 16:09 ` Trond Myklebust
2016-04-01 16:19 ` Jeff Layton [this message]
2016-04-01 20:24 ` Frank Filz
2016-04-01 16:35 ` Benjamin Coddington
2016-04-01 16:09 ` Jeff Layton
2016-04-01 17:17 ` Benjamin Coddington
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