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

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Message-ID: <CA+a=Yy5GKMu8rbh8y3fOtK6pmqygPNBr=a+p7LfcmTqtXFH3iA@mail.gmail.com>
Date:	Tue, 29 Nov 2011 23:10:16 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	"Myklebust, Trond" <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 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.

-- 
Thanks,
Tao
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