linux-kernel - Re: [PATCH] slab.h: Avoid using & for logical and of booleans

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Message-ID: <1541464370.196084.166.camel@acm.org>
Date:   Mon, 05 Nov 2018 16:32:50 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     linux@...musvillemoes.dk,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Christoph Lameter <cl@...ux.com>, guro@...com,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] slab.h: Avoid using & for logical and of booleans

On Mon, 2018-11-05 at 16:11 -0800, Alexander Duyck wrote:
> If we really don't care then why even bother with the switch statement
> anyway? It seems like you could just do one ternary operator and be
> done with it. Basically all you need is:
> return (defined(CONFIG_ZONE_DMA) && (flags & __GFP_DMA)) ? KMALLOC_DMA :
>         (flags & __GFP_RECLAIMABLE) ? KMALLOC_RECLAIM : 0;
> 
> Why bother with all the extra complexity of the switch statement?

I don't think that defined() can be used in a C expression. Hence the
IS_ENABLED() macro. If you fix that, leave out four superfluous parentheses,
test your patch, post that patch and cc me then I will add my Reviewed-by.

Bart.