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| author | Mike Rapoport (Microsoft) <rppt@kernel.org> | 2026-07-01 23:09:32 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-07-30 19:40:32 -0700 |
| commit | 5491b25d4ae99a59cada18aa03e0ac838b5fd725 (patch) | |
| tree | 9e215b8e8490ac598d99118f1eebae81ec9ca90b /tools | |
| parent | 6a8024511ddf4877435c34fb3d6028aa8e590649 (diff) | |
| download | linux-next-5491b25d4ae99a59cada18aa03e0ac838b5fd725.tar.gz linux-next-5491b25d4ae99a59cada18aa03e0ac838b5fd725.zip | |
selftests/mm/uffd: don't treat UFFDIO_COPY -ENOENT as a failure
Non-cooperarive uffd events are inherently racy and can happen in parallel
with other userfaultfd operations.
During event tests in uffd-unit-tests, the uffd monitor calls
UFFDIO_UNREGISTER upon receiving UFFD_EVENT_REMOVE.
In parallel, the faulting_process() verifies that the removed memory is
actually zeroed.
If a verification read wins the race with UFFDIO_UNREGISTER, it causes a
missing fault that uffd monitor would receive after UFFDIO_UNREGISTER is
complete. The monitor resolves the fault using UFFDIO_COPY that fails
with -ENOENT which means that VMA has been changed (see commit
27d02568f529 ("userfaultfd: mcopy_atomic: return -ENOENT when no
compatible VMA found")).
Treat -ENOENT returned by UFFDIO_COPY as non-fatal, the same way -EEXIST
is treated for concurrent faults, and don't fail the test.
Link: https://lore.kernel.org/20260701200932.1470525-1-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/mm/uffd-common.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c index edd02328f77b..f48f5d4594ab 100644 --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -639,8 +639,13 @@ int __copy_page(uffd_global_test_opts_t *gopts, unsigned long offset, bool retry uffdio_copy.mode = 0; uffdio_copy.copy = 0; if (ioctl(gopts->uffd, UFFDIO_COPY, &uffdio_copy)) { - /* real retval in ufdio_copy.copy */ - if (uffdio_copy.copy != -EEXIST) + /* + * real retval in uffdio_copy.copy + * + * -EEXIST: the page was faulted in concurrently + * -ENOENT: the destination range was concurrently removed + */ + if (uffdio_copy.copy != -EEXIST && uffdio_copy.copy != -ENOENT) err("UFFDIO_COPY error: %"PRId64, (int64_t)uffdio_copy.copy); wake_range(gopts->uffd, uffdio_copy.dst, gopts->page_size); |