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Date: Fri, 24 Nov 2017 14:28:57 +0100
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v2 1/2] mm,vmscan: Make unregister_shrinker() no-op if
 register_shrinker() failed.
Message-ID: <20171124132857.vi4t7szmbknywng7@dhcp22.suse.cz>
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To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, glauber@scylladb.com, syzkaller@googlegroups.com

On Fri 24-11-17 22:21:55, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > Since we can encourage register_shrinker() callers to check for failure
> > > by marking register_shrinker() as __must_check, unregister_shrinker()
> > > can stay silent.
> > 
> > I am not sure __must_check is the right way. We already do get
> > allocation warning if the registration fails so silent unregister is
> > acceptable. Unchecked register_shrinker is a bug like any other
> > unchecked error path.
> 
> I consider that __must_check is the simplest way to find all of
> unchecked register_shrinker bugs. Why not to encourage users to fix?

because git grep doesn't require to patch the kernel and still provide
the information you want. I would understand __must_check if we had
hundreds users of this api and they come and go quickly.

-- 
Michal Hocko
SUSE Labs

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