[Devel] Re: [PATCH] remove BUG() in possible but rare condition

[Glauber Costa]

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.