linux-kernel - Re: [PATCH] slab: fix 'dubious: x & !y' warning from Sparse

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Message-ID: <20181116170406.GM14706@dhcp22.suse.cz>
Date:   Fri, 16 Nov 2018 18:04:06 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] slab: fix 'dubious: x & !y' warning from Sparse

On Fri 16-11-18 13:51:19, Cristopher Lameter wrote:
> On Fri, 16 Nov 2018, Masahiro Yamada wrote:
> 
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 918f374..d395c73 100644
> > --- 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;
> >  }
> 
> Ok then lets revert the initial patch whose point was to avoid a branch.
> && causes a branch again.

I believe Vlastimil managed to get rid of the branch http://lkml.kernel.org/r/aa5975b6-58ed-5a3e-7de1-4b1384f88457@suse.cz

-- 
Michal Hocko
SUSE Labs