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Date: Thu, 23 Nov 2017 14:55:40 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Michal Hocko <mhocko@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.cz>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        LKML <linux-kernel@vger.kernel.org>,
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        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2] fs: handle shrinker registration failure in
 sget_userns
Message-ID: <20171123145540.GB21978@ZenIV.linux.org.uk>
References: <20171123115247.30685-1-mhocko@kernel.org>
 <20171123143537.ztpxpk3sjbpo72rf@dhcp22.suse.cz>
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On Thu, Nov 23, 2017 at 03:35:37PM +0100, Michal Hocko wrote:
> Hopefully less screwed version.  But as I've said I am not really
> familiar with the code and do not feel competent to change it so please
> be very careful here. I've moved the shrinker registration to
> alloc_super which turned out to be simpler.

I don't get it.  Why the hell do we need all that PITA in the first place?
Just make sget_userns() end with
	if (unlikely(regsiter_shrinker(&s->s_shrink) != 0)) {
		deactivate_locked_super(s);
		s = ERR_PTR(-ENOMEM);
	}
	return s;
and be done with that.  All there is to it...