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From: kan.liang@intel.com
To: acme@redhat.com
Cc: linux-kernel@vger.kernel.org, xiakaixu@huawei.com,
	a.p.zijlstra@chello.nl, ak@linux.intel.com,
	Kan Liang <kan.liang@intel.com>
Subject: [PATCH 1/1] Revert "perf: Remove the extra validity check on nr_pages"
Date: Mon,  2 Mar 2015 02:14:26 -0500	[thread overview]
Message-ID: <1425280466-7830-1-git-send-email-kan.liang@intel.com> (raw)

From: Kan Liang <kan.liang@intel.com>

This reverts commit 74390aa55678 ("perf: Remove the extra validity check
on nr_pages")

nr_pages equals to number of pages - 1 in perf_mmap. So nr_pages = 0 is
valide. So the nr_pages != 0 && !is_power_of_2(nr_pages) are all
needed for checking. Otherwise, for example, perf test 6 failed.
perf test 6
 6: x86 rdpmc test                                         :Error:
mmap() syscall returned with (Invalid argument)
 FAILED!

Signed-off-by: Kan Liang <kan.liang@intel.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 89f0f16..a83581c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4423,7 +4423,7 @@ 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 (!is_power_of_2(nr_pages))
+	if (nr_pages != 0 && !is_power_of_2(nr_pages))
 		return -EINVAL;
 
 	if (vma_size != PAGE_SIZE * (1 + nr_pages))
-- 
1.8.3.1


             reply	other threads:[~2015-03-02 14:23 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-02  7:14 kan.liang [this message]
2015-03-02 21:03 ` Arnaldo Carvalho de Melo
2015-03-03  6:26 ` [tip:perf/core] " tip-bot for Kan Liang
2015-03-03  8:44   ` Ingo Molnar
2015-03-03 20:04     ` Liang, Kan
2015-03-04  4:46       ` Ingo Molnar
2015-03-04 14:06         ` Liang, Kan
2015-03-04 20:28           ` Ingo Molnar

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