linux-kernel - [PATCH] perf/ring_buffer: Fix invalid page order

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Date:   Tue, 15 Nov 2016 16:15:59 +0900
From:   Takao Indoh <indou.takao@...fujitsu.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: [PATCH] perf/ring_buffer: Fix invalid page order

In rb_alloc_aux_page(), a page order is set to MAX_ORDER when order is
greater than MAX_ORDER, but page order should be less than MAX_ORDER,
therefore alloc_pages_node fails at least once. This patch fixes page
order so that it can be always less than MAX_ORDER.

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.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 257fa46..3f76fdd 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -502,8 +502,8 @@ 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);
-- 
1.8.3.1