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

From: Stanislav Kinsbursky
Date: Tue Dec 11 2012 - 09:58:14 EST


11.12.2012 18:54, Al Viro ÐÐÑÐÑ:
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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