From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 19446431E6A; Wed, 1 Jul 2026 20:01:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782936111; cv=none; b=GX8toxgIWkbjWtfpEyfkrQ5FkkHhAzrcn058ouWlnx59FwfalBN7gY7em58kRUTv3fNHVwHXhNnjNvVeVP7vIAgeWBTWeFWaxLyMUKOclv26/3pN05/GX66bRoXhKX4NjNy44pLEMQCdVCcuxnplbOByiJyy49I6gl34D0C38tk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782936111; c=relaxed/simple; bh=b8yHUUqkzlIXIOKJeOyubq8L2y3biOHEfHZccZ6kLrY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=JOmnWQPCMkf/qhEize/APpIiK0PrYfh/EI8hx71N+z0VMFqoxOoe0seqD7neSBNLZSMO5VsJNMI7xkV6FFy2lSW+rG26w8lnTofU5CFXYTVsQYUtZnInlrNG3QAakYmkZzpGl8IYNR8bCwrXjAejO8N1egj4alVtb7guIpXNIY4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BJsV/rpY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BJsV/rpY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCB881F000E9; Wed, 1 Jul 2026 20:01:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782936109; bh=TvSshaYaWYRW+SwJgWNvjOVVLpEc9oved1ALiTQdTMw=; h=From:To:Cc:Subject:Date; b=BJsV/rpYN3/oOqsrMhJz1343YzEzPMHR27/2V0TQjFe9hc3zIc9JLgIxIlY2C/KEP iTxCkBJFygaLbVRj0erQ5ybf7DqFpALF+UrmJDx//C/h4mWich5eGhOZy/Vq/bHwmT +gs3YilM4KQybhjdSdx43ilEL2U5PKBlBtYOl2hmkXl3efW4dqqpeqsHIIj0NOYIAi hEVIaub6QNxzp8VXkOBt4SgqrG4MlJFZI3H25qurJ6E8W0AQuxnrr3feEctLtA8mHn LNwmJXAd34CyUj2KJ/p3fnU+Yb7W7Lq9B3h2Qw/VqDo4HTYk2NgtfpZmJPKA0qZJAc 7+27+9FBYJRgQ== From: Mike Rapoport To: Andrew Morton , David Hildenbrand Cc: "Liam R. 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 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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