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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Peter Xu , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] dev: selftests/mm/uffd: don't treat UFFDIO_COPY -ENOENT as a failure Date: Wed, 1 Jul 2026 23:01:43 +0300 Message-ID: <20260701200143.1470229-1-rppt@kernel.org> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 08CDAC0011 X-Rspam-User: X-Stat-Signature: 46fuiu7qg4dozem49c1qkpbhm8bxb13g X-HE-Tag: 1782936110-137427 X-HE-Meta: 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 2C8Kpo+2 N4cLqcAAZ8p/qXvmx7vTH6QN3q3a1bIo47X3tKZ8coWD+HkBmzjOo1ylhnJQoJfB6gkT1NojelJh0hIMOHfWE3V4O8ugXBnZJOqrYFnRnEs4zSSzBA8n2BKragONu2/VfsWP7VbwORtk7SjZFs9x++AAZtmeOd9/E7xRv+H0Ua+pqsA+NF0yttkb3GofrTiNWaFzWkATGV97P29OCrv5gC6UVOCZIccZ4kZmS/uALYlP/57yi/6pVL4T8HPjrAWuuC/WsrQCiPwpkwYHT36BVsC82wui9yurj+W9nFC80mYR2FD+6N0WNAAUkXA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" 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. Signed-off-by: Mike Rapoport (Microsoft) --- I've noticed transient faults of uffd-unit-tests in the CI runs [1] and found this issue with uffd-unit-tests. The issue is longstanding and it's not related to or exposed by the recent uffd refactoring. I didn't even look for a Fixes: commit, as this is a selftest only and I don't see a reason to backport it. [1] https://github.com/linux-mm/linux-mm/actions tools/testing/selftests/mm/uffd-common.c | 9 +++++++-- 1 file 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); base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 -- 2.53.0