linux-kernel - Re: [PATCH 2/6] nfsd: swap fs root in NFSd kthreads

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Date:	Tue, 11 Dec 2012 18:57:36 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	"J. Bruce Fields" <bfields@...ldses.org>,
	<linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<devel@...nvz.org>
Subject: Re: [PATCH 2/6] nfsd: swap fs root in NFSd kthreads

11.12.2012 18:54, Al Viro пишет:
> On Tue, Dec 11, 2012 at 06:00:00PM +0400, Stanislav Kinsbursky wrote:
>> 11.12.2012 00:28, J. Bruce Fields ??????????:
>>> On Thu, Dec 06, 2012 at 06:34:47PM +0300, Stanislav Kinsbursky wrote:
>>>> NFSd does lookup. Lookup is done starting from current->fs->root.
>>>> NFSd is a kthread, cloned by kthreadd, and thus have global (but luckely
>>>> unshared) root.
>>>> So we have to swap root to those, which process, started NFSd, has. Because
>>>> that process can be in a container with it's own root.
>>>
>>> This doesn't sound right to me.
>>>
>>> Which lookups exactly do you see being done relative to
>>> current->fs->root ?
>>>
>>
>> Ok, you are right. I was mistaken here.
>> This is not a exactly lookup, but d_path() problem in svc_export_request().
>> I.e. without root swapping, d_path() will give not local export path (like "/export")
>> but something like this "/root/containers_root/export".
>
> Now, *that* is a different story (and makes some sense).  Take a look
> at __d_path(), please.  You don't need to set ->fs->root to get d_path()
> equivalent relative to given point.
>

Thanks, Al.
But __d_path() is not exported and this code is called from NFSd module.
Is it suitable for you to export __d_path()?

-- 
Best regards,
Stanislav Kinsbursky
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