linux-kernel - [PATCH 38/43] perf: Remove the extra validity check on nr

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Message-Id: <1423860572-24881-39-git-send-email-acme@kernel.org>
Date:	Fri, 13 Feb 2015 17:49:27 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Kaixu Xia <xiakaixu@...wei.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 38/43] perf: Remove the extra validity check on nr_pages

From: Kaixu Xia <xiakaixu@...wei.com>

The function is_power_of_2() also do the check on nr_pages, so the first
check performed is unnecessary. On the other hand, the key point is to
ensure @nr_pages is a power-of-two number and mostly @nr_pages is a
nonzero value, so in the most cases, the function is_power_of_2() will
be called.

Signed-off-by: Kaixu Xia <xiakaixu@...wei.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Link: http://lkml.kernel.org/r/1422352512-75150-1-git-send-email-xiakaixu@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7f2fbb8b5069..0969c9b67eec 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4420,7 +4420,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 	 * If we have rb pages ensure they're a power-of-two number, so we
 	 * can do bitmasks instead of modulo.
 	 */
-	if (nr_pages != 0 && !is_power_of_2(nr_pages))
+	if (!is_power_of_2(nr_pages))
 		return -EINVAL;
 
 	if (vma_size != PAGE_SIZE * (1 + nr_pages))
-- 
1.9.3

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