[PATCH] mm/gup_benchmark: fix unsigned comparison with less than zero

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

Currently the return from get_user_pages_fast is being checked
to be less than zero for an error check, however, the variable being
checked is unsigned so the check is always false. Fix this by using
a signed long instead.

Detected by Coccinelle ("Unsigned expression compared with zero: nr <= 0")

Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() 
benchmarking")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 mm/gup_benchmark.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 6a473709e9b6..a9a15e7a1185 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -31,6 +31,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
        nr = gup->nr_pages_per_call;
        start_time = ktime_get();
        for (addr = gup->addr; addr < gup->addr + gup->size; addr = next) {
+               long n;
+
                if (nr != gup->nr_pages_per_call)
                        break;
 
@@ -40,10 +42,10 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
                        nr = (next - addr) / PAGE_SIZE;
                }
 
-               nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
-               if (nr <= 0)
+               n = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
+               if (n <= 0)
                        break;
-               i += nr;
+               i += n;
        }
        end_time = ktime_get();
 
-- 
2.17.1