linux-kernel - Re: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference from blocklayout routines

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Message-ID: <1322584830.4174.16.camel@lade.trondhjem.org>
Date:	Tue, 29 Nov 2011 11:40:30 -0500
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Peng Tao <bergwolf@...il.com>
Cc:	tao.peng@....com, skinsbursky@...allels.com,
	linux-nfs@...r.kernel.org, xemul@...allels.com, neilb@...e.de,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	jbottomley@...allels.com, bfields@...ldses.org,
	davem@...emloft.net, devel@...nvz.org
Subject: Re: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference from
 blocklayout routines

On Tue, 2011-11-29 at 23:30 +0800, Peng Tao wrote: 
> On Tue, Nov 29, 2011 at 11:18 PM, Trond Myklebust
> <Trond.Myklebust@...app.com> wrote:
> > On Tue, 2011-11-29 at 23:10 +0800, Peng Tao wrote:
> >> On Tue, Nov 29, 2011 at 9:35 PM, Myklebust, Trond
> >> <Trond.Myklebust@...app.com> wrote:
> >> >> -----Original Message-----
> >> >> From: tao.peng@....com [mailto:tao.peng@....com]
> >> >> Sent: Tuesday, November 29, 2011 7:40 AM
> >> >> To: skinsbursky@...allels.com
> >> >> Cc: Myklebust, Trond; linux-nfs@...r.kernel.org; xemul@...allels.com;
> >> >> neilb@...e.de; netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> >> >> jbottomley@...allels.com; bfields@...ldses.org; davem@...emloft.net;
> >> >> devel@...nvz.org
> >> >> Subject: RE: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference
> >> >> from blocklayout routines
> >> >>
> >> >> > -----Original Message-----
> >> >> > From: Stanislav Kinsbursky [mailto:skinsbursky@...allels.com]
> >> >> > Sent: Tuesday, November 29, 2011 8:19 PM
> >> >> > To: Peng, Tao
> >> >> > Cc: Trond.Myklebust@...app.com; linux-nfs@...r.kernel.org; Pavel
> >> >> > Emelianov; neilb@...e.de; netdev@...r.kernel.org;
> >> >> > linux-kernel@...r.kernel.org; James Bottomley; bfields@...ldses.org;
> >> >> > davem@...emloft.net; devel@...nvz.org
> >> >> > Subject: Re: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference
> >> >> > from blocklayout routines
> >> >> >
> >> >> > 29.11.2011 16:00, tao.peng@....com пишет:
> >> >> > >> -----Original Message-----
> >> >> > >> From: linux-nfs-owner@...r.kernel.org
> >> >> > >> [mailto:linux-nfs-owner@...r.kernel.org] On Behalf Of
> >> >> > Stanislav
> >> >> > >> Kinsbursky
> >> >> > >> Sent: Tuesday, November 29, 2011 6:11 PM
> >> >> > >> To: Trond.Myklebust@...app.com
> >> >> > >> Cc: linux-nfs@...r.kernel.org; xemul@...allels.com; neilb@...e.de;
> >> >> > >> netdev@...r.kernel.org; linux- kernel@...r.kernel.org;
> >> >> > >> jbottomley@...allels.com; bfields@...ldses.org;
> >> >> > >> davem@...emloft.net; devel@...nvz.org
> >> >> > >> Subject: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference
> >> >> > >> from blocklayout routines
> >> >> > >>
> >> >> > >> This is a cleanup patch. We don't need this reference anymore,
> >> >> > >> because blocklayout pipes dentries now creates and destroys in
> >> >> > >> per-net operations and on PipeFS mount/umount notification.
> >> >> > >> Note that nfs4blocklayout_register_net() now returns 0 instead of
> >> >> > >> -ENOENT in case of PipeFS superblock absence. This is ok, because
> >> >> > >> blocklayout pipe dentry will be created on PipeFS mount event.
> >> >> > > When is the "pipefs mount event" going to happen? When inserting
> >> >> > > kernel modules or when user issues
> >> >> > mount command?
> >> >> > >
> >> >> >
> >> >> > When user issues mount command.
> >> >> > Kernel mounts of PipeFS has been removed with all these patch sets
> >> >> > I've sent already.
> >> >> Then it is going to break blocklayout user space program blkmapd, which is
> >> >> stared before mounting any file system and it tries to open the pipe file
> >> >> when started.
> >> >
> >> > Why on earth is blkmapd doing this instead of listening for file creation notifications like the other rpc_pipefs daemons do?
> >> Not sure how the original implementer chose this but I think it is
> >> likely because we do not expect the pipe file to be created or deleted
> >> dynamically.
> >
> > Unless blkmapd can pin the sunrpc module (which it shouldn't be able to)
> > then that assumption would be wrong. Please look into fixing blkmapd...
> Sorry, I don't quite get it. Do you mean sunrpc module may be removed
> while nfs/blocklayout modules are still in use? Please explain it a
> bit. Thanks.

I mean that I'm perfectly entitled to do

'modprobe -r blocklayoutdriver'

and when I do that, then I expect blkmapd to close the rpc pipe and wait
for a new one to be created just like rpc.idmapd and rpc.gssd do when I
remove the nfs and sunrpc modules.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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