linux-kernel - Re: [PATCH] Revert "__d_unalias() should refuse to move mountpoints"

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Message-ID: <8db34325-e8e4-4e24-85dd-c8951769e2b6@email.android.com>
Date:	Tue, 25 Sep 2012 00:05:12 -0700
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
CC:	al viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "__d_unalias() should refuse to move mountpoints"

Maarten Lankhorst <maarten.lankhorst@...onical.com> wrote:

>Hey,
>
>Op 25-09-12 05:39, Eric W. Biederman schreef:
>> Maarten Lankhorst <maarten.lankhorst@...onical.com> writes:
>>
>>> This reverts commit ee3efa91e240f513898050ef305a49a653c8ed90.
>>>
>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@...onical.com>
>>>
>>> My thread about the regression seemed to have been ignored, so I can
>only
>>> conclude nobody objects against a full revert of this patch.
>>>
>>> My testcase is simply booting through netboot with / and ~/nfs as
>separate
>>> nfs filesystems, then doing 'ls ~/nfs' followed by 'ls ~' in a
>gnome-terminal
>>> window, then I get:
>> Do I read your description correctly:  Without using a bind mount you
>> have the same nfs filesystem mounted on / and on ~/nfs?
>>
>> Something is definitely off with your configuration but if to work
>you
>> need to move mount points around then that something seems much
>deeper
>> than the __d_unalias change.
>>
>> What filesystems do you have mounted where?
>>
>/ is a nfs filesystem, ~/nfs is a different nfs filesystem.

Are both filesystems on the same server?

Are the two filesystems distinct filesystem on the server?

Unless there is duplication of something somewhere the d_unalias code should not trigger.

> Just doing
>ls / is enough
>to make all filesystems mounted on / return -EBUSY and disappear.
>
>I also have a subdir of ~/nfs/ bind mounted to /lib/modules/$(uname
>-r)/kernel
>for easy debugging so just doing 'make' in the kernel tree is enough to
>get the
>new modules + bzImage, but I don't know if it is a factor in
>reproducing this bug
>or not.

Unlikely.  But interesting.  It at least fits the criteria of showing up to different places.  It should not be enough for d_materialise uniqe.

Eric


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