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

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Message-ID: <CAKYAXd__BLFPOw=+tt=cqZgyM45y5mSOTamVaFTU26BNSNa=2A@mail.gmail.com>
Date:	Thu, 12 Jul 2012 07:38:22 +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.

2012/7/11, 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.
>
> --b.
>
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