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Date: Tue, 21 Aug 2018 12:36:34 +0100 From: Colin King <colin.king@...onical.com> To: Andrew Morton <akpm@...ux-foundation.org>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, "Michael S . Tsirkin" <mst@...hat.com>, linux-mm@...ck.org Cc: kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH] mm/gup_benchmark: fix unsigned comparison with less than zero From: Colin Ian King <colin.king@...onical.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@...onical.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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