From: John Hubbard Date: Wed, 6 Nov 2019 05:16:24 +0000 (-0800) Subject: mm/gup_benchmark: fix MAP_HUGETLB case X-Git-Tag: baikal/mips/sdk5.9~15008^2~15 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=94baaa5a33e3686b0c1ae5bf51064727ac466260;p=kernel.git mm/gup_benchmark: fix MAP_HUGETLB case The MAP_HUGETLB ("-H" option) of gup_benchmark fails: $ sudo ./gup_benchmark -H mmap: Invalid argument This is because gup_benchmark.c is passing in a file descriptor to mmap(), but the fd came from opening up the /dev/zero file. This confuses the mmap syscall implementation, which thinks that, if the caller did not specify MAP_ANONYMOUS, then the file must be a huge page file. So it attempts to verify that the file really is a huge page file, as you can see here: ksys_mmap_pgoff() { if (!(flags & MAP_ANONYMOUS)) { retval = -EINVAL; if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file))) goto out_fput; /* THIS IS WHERE WE END UP */ else if (flags & MAP_HUGETLB) { ...proceed normally, /dev/zero is ok here... ...and of course is_file_hugepages() returns "false" for the /dev/zero file. The problem is that the user space program, gup_benchmark.c, really just wants anonymous memory here. The simplest way to get that is to pass MAP_ANONYMOUS whenever MAP_HUGETLB is specified, so that's what this patch does. Link: http://lkml.kernel.org/r/20191021212435.398153-2-jhubbard@nvidia.com Signed-off-by: John Hubbard Reviewed-by: Andrew Morton Reviewed-by: Jérôme Glisse Cc: Keith Busch Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c index cb3fc09645c48..485cf06ef013f 100644 --- a/tools/testing/selftests/vm/gup_benchmark.c +++ b/tools/testing/selftests/vm/gup_benchmark.c @@ -71,7 +71,7 @@ int main(int argc, char **argv) flags |= MAP_SHARED; break; case 'H': - flags |= MAP_HUGETLB; + flags |= (MAP_HUGETLB | MAP_ANONYMOUS); break; default: return -1;