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Date: Tue, 21 Nov 2017 13:40:07 -0800
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm,vmscan: Mark register_shrinker() as __must_check
Message-Id: <20171121134007.466815aa4a0562eaaa223cbf@linux-foundation.org>
In-Reply-To: <1511265757-15563-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
References: <1511265757-15563-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
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Sender: owner-linux-mm@kvack.org
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To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-mm@kvack.org, Dave Chinner <david@fromorbit.com>, Al Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.com>, Paolo Bonzini <pbonzini@redhat.com>, David Airlie <airlied@linux.ie>, Alex Deucher <alexander.deucher@amd.com>, Shaohua Li <shli@fb.com>, Mike Snitzer <snitzer@redhat.com>

On Tue, 21 Nov 2017 21:02:37 +0900 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:

> There are users not checking for register_shrinker() failure.
> Continuing with ignoring failure can lead to later oops at
> unregister_shrinker().
> 
> ...
>
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -75,6 +75,6 @@ struct shrinker {
>  #define SHRINKER_NUMA_AWARE	(1 << 0)
>  #define SHRINKER_MEMCG_AWARE	(1 << 1)
>  
> -extern int register_shrinker(struct shrinker *);
> +extern __must_check int register_shrinker(struct shrinker *);
>  extern void unregister_shrinker(struct shrinker *);
>  #endif

hm, well, OK, it's a small kmalloc(GFP_KERNEL).  That won't be
failing.

Affected code seems to be fs/xfs, fs/super.c, fs/quota,
arch/x86/kvm/mmu, drivers/gpu/drm/ttm, drivers/md and a bunch of
staging stuff.

I'm not sure this is worth bothering about?

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