Message-ID: <93b37049-af7e-3408-37bf-805f633271e4@suse.cz>
Date:   Tue, 21 Mar 2023 09:00:03 +0100
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Subject: Re: [PATCH 06/10] perf/core: Fix MAX_ORDER usage in
 rb_alloc_aux_page()
Content-Language: en-US
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>,
        David Hildenbrand <david@redhat.com>
Cc:     linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>
References: <20230315113133.11326-1-kirill.shutemov@linux.intel.com>
 <20230315113133.11326-7-kirill.shutemov@linux.intel.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20230315113133.11326-7-kirill.shutemov@linux.intel.com>
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Precedence: bulk

On 3/15/23 12:31, 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 rb_alloc_aux_page().
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Ian Rogers <irogers@google.com>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  kernel/events/ring_buffer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 273a0fe7910a..d6bbdb7830b2 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>  {
>  	struct page *page;
>  
> -	if (order > MAX_ORDER)
> -		order = MAX_ORDER;
> +	if (order >= MAX_ORDER)
> +		order = MAX_ORDER - 1;
>  
>  	do {
>  		page = alloc_pages_node(node, PERF_AUX_GFP, order);