linux-kernel - Re: [PATCH] nfs-util: Add cache_flush in mountd UMNT procedure.

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Message-ID: <CAKYAXd9KLxDqXSqgk7Y1rNv9cw-r+PHPSenQCnkRh9_0_6HmAQ@mail.gmail.com>
Date:	Thu, 12 Jul 2012 07:43:49 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	SteveD@...hat.com, Trond.Myklebust@...app.com,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vivek Trivedi <vtrivedi018@...il.com>
Subject: Re: [PATCH] nfs-util: Add cache_flush in mountd UMNT procedure.

2012/7/12, Namjae Jeon <linkinjeon@...il.com>:
> 2012/7/11, J. Bruce Fields <bfields@...ldses.org>:
>> On Wed, Jul 11, 2012 at 01:10:53PM +0900, Namjae Jeon wrote:
>>> 2012/7/10, J. Bruce Fields <bfields@...ldses.org>:
>>> > On Sat, Jul 07, 2012 at 11:17:39PM -0400, Namjae Jeon wrote:
>>> >> For removing storage device - user needs to safely un-mount the
>>> >> device
>>> >> and then eject. But if 'EBUSY' occurs in umount then it will create
>>> >> confusion for the user as it will mean some I/O is in progress - and
>>> >> won't allow user to safely ejecting device.
>>> >
>>> Hi James.
>>> > The one drawback is that recovering from the cache flushes might be a
>>> > little expensive if you have a lot of exports in use.
>>> Good point. I will look for more there is the method flush only mount
>>> entry.
>>
>> I don't think there's a good way to flush only one entry.
>>
>> Also, this isn't going to help for NFSv4 since a v4 client won't do an
>> unmount call.
> Okay.
>>
>>> > I'm curious, since you said this was for a usb disk: are users
>>> > expected
>>> > to just unplug it (in which case--is it read only?) or do they have
>>> > some
>>> > way of unmounting before they pull the plug?
>>> Users expected to unplug it on both read only and read/write.
>>> And there is no way that system be prepared to know about the
>>> intelligence when the user is going to unplug.
>>> if the user really want to detach the device safely. There is an
>>> option like the desktop PC - where, we can say - umount/eject the
>>> device. There is a proper user interface for safe removal.
>>> but they can not unplug safely if usb device is mounted with nfs
>>> because of this issue.
>>
>> Ideal might be to get some way to notify nfsd when the device
>> diseappears or the filesystem wants to unmount.  I don't know how to do
>> that.
> Okay. I will look for good solution for this issue.
> Thanks.
Hi James.
I have a question.
If we found the method to notify nfs when unplugging device, Can nfsd
flush only entry of usb mount ?

Thanks.

>>
>> --b.
>>
>
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