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authorJohn Hubbard <jhubbard@nvidia.com>2019-11-05 21:16:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-06 08:28:58 -0800
commit64801d19eba156170340c76f70ade743defcb8ce (patch)
tree3be442d9dceee15e81f58d8e298dcbb861714f9a /tools/testing/selftests/vm
parent7961eee3978475fd9e8626137f88595b1ca05856 (diff)
downloadlinux-64801d19eba156170340c76f70ade743defcb8ce.tar.bz2
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 <jhubbard@nvidia.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jérôme Glisse <jglisse@redhat.com> Cc: Keith Busch <keith.busch@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'tools/testing/selftests/vm')
-rw-r--r--tools/testing/selftests/vm/gup_benchmark.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c
index cb3fc09645c4..485cf06ef013 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;