Revert "perf: Remove the extra validity check on nr_pages"

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
valid.

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>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1425280466-7830-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index af924bc381218ac2407f88814b7d3ae0777c0f09..8bb20cc39a9248e7b6c2d97e37490ae83218d2f2 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4446,7 +4446,7 @@ 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))