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Subject[PATCH] mm/gup_benchmark: fix unsigned comparison with less than zero
Date
From: Colin Ian King <colin.king@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.king@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
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