Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile

From	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile
Date	2015-07-13 09:00 +0200
Message-ID	<pLFSy-1Lw-15@gated-at.bofh.it> (permalink)
References	<pKWC6-8du-13@gated-at.bofh.it> <pKZTj-1Tn-11@gated-at.bofh.it> <pLfv3-2G0-1@gated-at.bofh.it> <pLFzb-1F6-7@gated-at.bofh.it>
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On (07/12/15 23:33), Christoph Hellwig wrote:
> On Sun, Jul 12, 2015 at 11:47:32AM +0900, Sergey Senozhatsky wrote:
> > Yes, but the main difference here is that it seems that shrinker users
> > don't tend to treat shrinker registration failures as fatal errors and
> > just continue with shrinker functionality disabled. And it makes sense.
> > 
> > (copy paste from https://lkml.org/lkml/2015/7/9/751)
> > 
> 
> I hearily disagree.  It's not any less critical than other failures.

Why? In some sense, shrinker callbacks are just a way to be nice.
No one writes a driver just to be able to handle shrinker calls. An
ability to react to those calls is just additional option; it does
not directly affect or limit driver's functionality (at least, it
really should not).

> The right way forward is to handle register failure properly.

In other words, to
 (a) keep a flag to signify that register was not successful
or
 (b) look at ->shrinker.list.next or ->nr_deferred
or
 (c) treat register failures as critical errors. (I sort of
     disagree with you here).

	-ss
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Thread

Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile Christoph Hellwig <hch@infradead.org> - 2015-07-11 12:10 +0200
  Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile Christoph Hellwig <hch@infradead.org> - 2015-07-13 08:40 +0200
    Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2015-07-13 09:00 +0200
      Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile Christoph Hellwig <hch@infradead.org> - 2015-07-13 11:10 +0200
        Re: [PATCH 0/2] mm/shrinker: make unregister_shrinker() less fragile Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2015-07-13 11:40 +0200

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