linux-kernel - Re: [PATCH] gfp: GFP_RECLAIM_MASK should include __GFP_NO

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Message-ID: <20151014073428.GC28333@dhcp22.suse.cz>
Date:	Wed, 14 Oct 2015 09:34:28 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Pan Xinhui <xinhuix.pan@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>, vbabka@...e.cz,
	rientjes@...gle.com, hannes@...xchg.org, nasa4836@...il.com,
	mgorman@...e.de, alexander.h.duyck@...hat.com,
	aneesh.kumar@...ux.vnet.ibm.com,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH] gfp: GFP_RECLAIM_MASK should include __GFP_NO_KSWAPD

On Wed 14-10-15 13:36:51, Pan Xinhui wrote:
> From: Pan Xinhui <xinhuix.pan@...el.com>
> 
> GFP_RECLAIM_MASK was introduced in commit 6cb062296f73 ("Categorize GFP
> flags"). In slub subsystem, this macro controls slub's allocation
> behavior. In particular, some flags which are not in GFP_RECLAIM_MASK
> will be cleared. So when slub pass this new gfp_flag into page
> allocator, we might lost some very important flags.
> 
> There are some mistakes when we introduce __GFP_NO_KSWAPD. This flag is
> used to avoid any scheduler-related codes recursive.  But it seems like
> patch author forgot to add it into GFP_RECLAIM_MASK. So lets add it now.

This is no longer needed because GFP_RECLAIM_MASK contains __GFP_RECLAIM
now - have  a look at
http://lkml.kernel.org/r/1442832762-7247-7-git-send-email-mgorman%40techsingularity.net
which is sitting in the mmotm tree.

> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
> ---
>  include/linux/gfp.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index f92cbd2..9ebad4d 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -130,7 +130,8 @@ struct vm_area_struct;
>  /* Control page allocator reclaim behavior */
>  #define GFP_RECLAIM_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS|\
>  			__GFP_NOWARN|__GFP_REPEAT|__GFP_NOFAIL|\
> -			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC)
> +			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\
> +			__GFP_NO_KSWAPD)
>  
>  /* Control slab gfp mask during early boot */
>  #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_WAIT|__GFP_IO|__GFP_FS))
> -- 
> 1.9.1

-- 
Michal Hocko
SUSE Labs
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