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Re: [PATCH] remove BUG() in possible but rare condition [message #45901 is a reply to message #45900]

Wed, 11 April 2012 20:51

Glauber Costa
Messages: 916
Registered: October 2011

Senior Member

On 04/11/2012 05:26 PM, Andrew Morton wrote:
>>
>> > failed:
>> > - BUG();
>> > unlock_page(page);
>> > page_cache_release(page);
>> > return NULL;
> Cute.
>
> AFAICT what happened was that in my April 2002 rewrite of this code I
> put a non-fatal buffer_error() warning in that case to tell us that
> something bad happened.
>
> Years later we removed the temporary buffer_error() and mistakenly
> replaced that warning with a BUG(). Only it*can* happen.
>
> We can remove the BUG() and fix up callers, or we can pass retry=1 into
> alloc_page_buffers(), so grow_dev_page() "cannot fail". Immortal
> functions are a silly fiction, so we should remove the BUG() and fix up
> callers.
>
Any particular caller you are concerned with ?

As I mentioned, this function already returns NULL for other reason -
that seem even more probable than this specific failure. So whoever is
not checking this return value, is already broken without this patch as
well.

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[Message index]

		[PATCH] remove BUG() in possible but rare condition By: Glauber Costa on Wed, 11 April 2012 18:10
		Re: [PATCH] remove BUG() in possible but rare condition By: Michal Hocko on Wed, 11 April 2012 18:48
		Re: [PATCH] remove BUG() in possible but rare condition By: Linus Torvalds on Wed, 11 April 2012 18:57
		Re: [PATCH] remove BUG() in possible but rare condition By: Glauber Costa on Wed, 11 April 2012 19:02
		Re: [PATCH] remove BUG() in possible but rare condition By: Michal Hocko on Wed, 11 April 2012 19:25
		Re: [PATCH] remove BUG() in possible but rare condition By: Michal Hocko on Wed, 11 April 2012 19:20
		Re: [PATCH] remove BUG() in possible but rare condition By: Jiri Kosina on Wed, 11 April 2012 21:33
		Re: [PATCH] remove BUG() in possible but rare condition By: Glauber Costa on Wed, 11 April 2012 18:59
		Re: [PATCH] remove BUG() in possible but rare condition By: akpm on Wed, 11 April 2012 20:26
		Re: [PATCH] remove BUG() in possible but rare condition By: Glauber Costa on Wed, 11 April 2012 20:51
		Re: [PATCH] remove BUG() in possible but rare condition By: akpm on Wed, 11 April 2012 21:12
		Re: [PATCH] remove BUG() in possible but rare condition By: Michal Hocko on Wed, 11 April 2012 21:26
		Re: [PATCH] remove BUG() in possible but rare condition By: Michal Hocko on Thu, 12 April 2012 09:24

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