diff options
| author | John Hubbard <jhubbard@nvidia.com> | 2019-11-05 21:16:24 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-11-06 08:28:58 -0800 |
| commit | 64801d19eba156170340c76f70ade743defcb8ce (patch) | |
| tree | 3be442d9dceee15e81f58d8e298dcbb861714f9a /tools/testing/selftests/vm | |
| parent | 7961eee3978475fd9e8626137f88595b1ca05856 (diff) | |
| download | linux-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.c | 2 |
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; |