mm/gup_benchmark: fix unsigned comparison to zero in __gup_benchmark_ioctl

get_user_pages_fast() will return negative value if no pages were pinned,
then be converted to a unsigned, which is compared to zero, giving the
wrong result.

Link: http://lkml.kernel.org/r/20180921095015.26088-1-yuehaibing@huawei.com
Fixes: 09e35a4a1ca8 ("mm/gup_benchmark: handle gup failures")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 6a47370..7405c9d 100644 (file)
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -19,7 +19,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
                struct gup_benchmark *gup)
 {
        ktime_t start_time, end_time;
-       unsigned long i, nr, nr_pages, addr, next;
+       unsigned long i, nr_pages, addr, next;
+       int nr;
        struct page **pages;
 
        nr_pages = gup->size / PAGE_SIZE;