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

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Message-ID: <CA+a=Yy6kJe0NemSiRwM+t8gz5-UF5fOdwdS2so+q=nSYjBx--w@mail.gmail.com>
Date:	Tue, 29 Nov 2011 23:30:22 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	Trond Myklebust <Trond.Myklebust@...app.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, 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.

Best,
Tao
>
>   Trond
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@...app.com
> www.netapp.com
>



-- 
Thanks,
Tao
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