Re: [REPOST] [PATCH 2/2] mm: Fix potentially scheduling in GFP_ATOMIC allocations.

[David Rientjes <rientjes@google.com>]

On Sun, 23 Aug 2015, Tetsuo Handa wrote:

> >From 08a638e04351386ab03cd1223988ac7940d4d3aa Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Date: Sat, 1 Aug 2015 22:46:12 +0900
> Subject: [PATCH 2/2] mm: Fix potentially scheduling in GFP_ATOMIC
>  allocations.
> 
> Currently, if somebody does GFP_ATOMIC | __GFP_NOFAIL allocation,
> wait_iff_congested() might be called via __alloc_pages_high_priority()
> before reaching
> 
>   if (!wait) {
>     WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
>     goto nopage;
>   }
> 
> because gfp_to_alloc_flags() includes ALLOC_NO_WATERMARKS if TIF_MEMDIE
> was set.
> 
> We need to check for __GFP_WAIT flag at __alloc_pages_high_priority()
> in order to make sure that we won't schedule.
> 

I've brought the GFP_ATOMIC | __GFP_NOFAIL combination up before, which 
resulted in the WARN_ON_ONCE() that you cited.  We don't support such a 
combination.  Fixing up the documentation in any places you feel it is 
deficient would be the best.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>