linux-kernel - Re: [PATCH 01/10] sparc/mm: Fix MAX_ORDER usage in tsb

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Message-ID: <20230316030437.GD3092@monkey>
Date:   Wed, 15 Mar 2023 20:04:37 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        sparclinux@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH 01/10] sparc/mm: Fix MAX_ORDER usage in tsb_grow()

On 03/15/23 14:31, Kirill A. Shutemov wrote:
> MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
> can deliver is MAX_ORDER-1.
> 
> Fix MAX_ORDER usage in tsb_grow().
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: sparclinux@...r.kernel.org
> Cc: David Miller <davem@...emloft.net>
> ---
>  arch/sparc/mm/tsb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/sparc/mm/tsb.c b/arch/sparc/mm/tsb.c
> index 912205787161..dba8dffe2113 100644
> --- a/arch/sparc/mm/tsb.c
> +++ b/arch/sparc/mm/tsb.c
> @@ -402,8 +402,8 @@ void tsb_grow(struct mm_struct *mm, unsigned long tsb_index, unsigned long rss)
>  	unsigned long new_rss_limit;
>  	gfp_t gfp_flags;
>  
> -	if (max_tsb_size > (PAGE_SIZE << MAX_ORDER))
> -		max_tsb_size = (PAGE_SIZE << MAX_ORDER);
> +	if (max_tsb_size > (PAGE_SIZE << (MAX_ORDER - 1)))
> +		max_tsb_size = (PAGE_SIZE << (MAX_ORDER - 1));
>  
>  	new_cache_index = 0;
>  	for (new_size = 8192; new_size < max_tsb_size; new_size <<= 1UL) {
> 

Fortunately, I think this only comes into play if MAX_ORDER <= 7.

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz