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From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Subject: Re: [PATCH] CIFS: Fix kernel crash on simultaneous mount/umount calls
Date: Sat, 11 Jun 2011 12:12:53 +0100
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Cc: Pavel Shilovsky <piastryyy-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
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On Sat, Jun 11, 2011 at 05:43:14AM -0400, Christoph Hellwig wrote:

> Ok, if we look at sb-private data in the sget callsbacks it seems like
> the clreanup for those does indeed need to be done in ->kill_sb.  I have
> to say I really hate it, and the culprit is that we call the sget test
> callback is called before we call grab_super in sget, that is we don't
> protect against filesystems going away.  I suspect that is the real
> problem here.

grab_super() is *heavy* and having to undo it even once means that we need to
rescan.  Sorry, test() has to be callable without that.