linux-kernel - Re: Dcache oops

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Message-Id: <DF4A1130-84CD-4083-92B4-6DEA2D633753@linuxhacker.ru>
Date:	Sat, 4 Jun 2016 12:12:14 -0400
From:	Oleg Drokin <green@...uxhacker.ru>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	"<linux-kernel@...r.kernel.org> Mailing List" 
	<linux-kernel@...r.kernel.org>,
	"<linux-fsdevel@...r.kernel.org>" <linux-fsdevel@...r.kernel.org>,
	linux-nfs@...r.kernel.org
Subject: Re: Dcache oops


On Jun 3, 2016, at 8:56 PM, Al Viro wrote:

> On Fri, Jun 03, 2016 at 07:58:37PM -0400, Oleg Drokin wrote:
> 
>>> EOPENSTALE, that is...  Oleg, could you check if the following works?
>> 
>> Yes, this one lasted for an hour with no crashing, so it must be good.
>> Thanks.
>> (note, I am not equipped to verify correctness of NFS operations, though).
> 
> I suspect that Jeff Layton might have relevant regression tests.  Incidentally,
> we really need a consolidated regression testsuite, including the tests you'd
> been running.  Right now there's some stuff in xfstests, LTP and cthon; if
> anything, this mess shows just why we need all of that and then some in
> a single place.  Lustre stuff has caught a 3 years old NFS bug (missing
> d_drop() in nfs_atomic_open()) and a year-old bug in handling of EOPENSTALE
> retries on the last component of a trailing non-embedded symlink.  Neither
> is hard to trigger; it's just that relevant tests hadn't been run on NFS,
> period.

BTW, the nets also have brought in another use after free in nfs4 state
tracking code (this is the one I was trying to hunt down from the start).
I'll submit a patch shortly.
And also there's a mysterious ext4 data corruption that I do not really fully
understand but only hit once so far.