linux-kernel - Re: [RFC PATCH] nfs: Add NFS3PROC

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Date:	Sun, 24 Jun 2012 14:12:49 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	Fields James <bfields@...ldses.org>
Cc:	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	Morton Andrew <akpm@...ux-foundation.org>,
	Harrosh Boaz <bharrosh@...asas.com>,
	"<linux-nfs@...r.kernel.org>" <linux-nfs@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Vivek Trivedi <t.vivek@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [RFC PATCH] nfs: Add NFS3PROC_UMOUNT procedure.

2012/6/24, Fields James <bfields@...ldses.org>:
> On Sat, Jun 23, 2012 at 11:57:10AM -0400, Fields James wrote:
>> On Sat, Jun 23, 2012 at 03:52:20PM +0000, Myklebust, Trond wrote:
>> > The other objection is that NFSv3 already has a way to do this via the
>> > MOUNT protocol. We already call MOUNTPROC3_UMNT/MOUNTPROC_UMNT on
>> > unmount of a filesystem.
>> >
>> > The problem with this approach is that if the NFS client crashes before
>> > it can call this function, then the server never gets notified. That is
>> > a problem that your patch has too...
>>
>> Yes.  Could you instead work on describing *exactly* what the original
>> problem was that prompted this?
>
> ("You" here meaning Namjae Jeon, of course).
>
> And note here we've all read the changelog, that's not what I'm asking
> for.
>
> I want to know the details of *your* specific case.  "I have X clients
> that I use for Y, periodically I want to unmount the exported filesystem
> to do Z, I tried doing W but it didn't work...".
As you remember, We discussed this
issue(http://www.spinics.net/lists/linux-nfs/msg29997.html) with you
before. you guided me to use exportfs -f call on nfs server.
It is hard to use this method on our system and nomally the user is
thinking it is problem device busy happen after umounting.

The details of specific case.
1. There are two target or two PC. and Client want to access files of
usb device on server.
2. the client try to mount usb mount point using nfs on sever after
plugging usb device.
3. we try to umount mount point directory on client.
4. and when we try to umount usb device mount directory server, device
busy message occured like this (umount: can't umount /mnt: Device or
resource busy)

Let me know in case you have any question.

Thanks.

>
> --b.
>
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