linux-kernel - Re: [PATCH 0/2] mm/shrinker: make unregister

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Message-ID: <20150711100232.GA4607@infradead.org>
Date:	Sat, 11 Jul 2015 03:02:32 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile

On Sat, Jul 11, 2015 at 11:51:53AM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> Shrinker API does not handle nicely unregister_shrinker() on a not-registered
> ->shrinker. Looking at shrinker users, they all have to
> (a) carry on some sort of a flag to make sure that "unregister_shrinker()"
> will not blow up later
> (b) be fishy (potentially can Oops)
> (c) access private members `struct shrinker' (e.g. `shrink.list.next')

Ayone who does that is broken.  You just need to have clear init (with
proper unwinding) and exit functions and order things properly.  It
works like most register/unregister calls and should stay that way.

Maye you you should ty to explain what practical problem you're seeing
to start with.
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