[06/10] perf/core: Fix MAX_ORDER usage in rb_alloc_aux_page()

Message ID 20230315113133.11326-7-kirill.shutemov@linux.intel.com
State New
Headers
Series Fix confusion around MAX_ORDER |

Commit Message

Kirill A. Shutemov March 15, 2023, 11:31 a.m. UTC
  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>
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(-)
  

Comments

Vlastimil Babka March 21, 2023, 8 a.m. UTC | #1
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);
  

Patch

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);