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Message-Id: <20181105131305.574d85469f08a4b76592feb6@linux-foundation.org>
Date: Mon, 5 Nov 2018 13:13:05 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Bart Van Assche <bvanassche@....org>
Cc: linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>,
Mel Gorman <mgorman@...hsingularity.net>,
Christoph Lameter <cl@...ux.com>, Roman Gushchin <guro@...com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org
Subject: Re: [PATCH] slab.h: Avoid using & for logical and of booleans
On Mon, 5 Nov 2018 12:40:00 -0800 Bart Van Assche <bvanassche@....org> wrote:
> This patch suppresses the following sparse warning:
>
> ./include/linux/slab.h:332:43: warning: dubious: x & !y
>
> ...
>
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -329,7 +329,7 @@ static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags)
> * If an allocation is both __GFP_DMA and __GFP_RECLAIMABLE, return
> * KMALLOC_DMA and effectively ignore __GFP_RECLAIMABLE
> */
> - return type_dma + (is_reclaimable & !is_dma) * KMALLOC_RECLAIM;
> + return type_dma + is_reclaimable * !is_dma * KMALLOC_RECLAIM;
> }
>
> /*
I suppose so.
That function seems too clever for its own good :(. I wonder if these
branch-avoiding tricks are really worthwhile.
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