linux-kernel - Re: [patch for-4.11] mm, thp: fix setting of defer+madvise thp defrag mode

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Message-ID: <20170406133901.GM5497@dhcp22.suse.cz>
Date:   Thu, 6 Apr 2017 15:39:03 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch for-4.11] mm, thp: fix setting of defer+madvise thp
 defrag mode

On Wed 05-04-17 18:17:42, David Rientjes wrote:
> Setting thp defrag mode of "defer+madvise" actually sets "defer" in the 
> kernel due to the name similarity and the out-of-order way the string is 
> checked in defrag_store().
> 
> Check the string in the correct order so that 
> TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG is set appropriately for 
> "defer+madvise".
> 
> Fixes: 21440d7eb904 ("mm, thp: add new defer+madvise defrag option") 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Acked-by: Michal Hocko <mhocko@...e.com>

I will just note that this wouldn't be necessary if you didn't ignore
the review feedback from Vlastimil [1].

[1] http://lkml.kernel.org/r/2099d74d-fa2c-e67e-b528-66598d072329@suse.cz

> ---
>  mm/huge_memory.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -240,18 +240,18 @@ static ssize_t defrag_store(struct kobject *kobj,
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
>  		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
> -	} else if (!memcmp("defer", buf,
> -		    min(sizeof("defer")-1, count))) {
> -		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
> -		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
> -		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
> -		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
>  	} else if (!memcmp("defer+madvise", buf,
>  		    min(sizeof("defer+madvise")-1, count))) {
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
>  		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
> +	} else if (!memcmp("defer", buf,
> +		    min(sizeof("defer")-1, count))) {
> +		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
> +		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
> +		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
> +		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
>  	} else if (!memcmp("madvise", buf,
>  			   min(sizeof("madvise")-1, count))) {
>  		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);

-- 
Michal Hocko
SUSE Labs