From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EC34C11F66 for ; Thu, 1 Jul 2021 01:48:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77ECB61468 for ; Thu, 1 Jul 2021 01:48:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238394AbhGABvU (ORCPT ); Wed, 30 Jun 2021 21:51:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:40636 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238384AbhGABvU (ORCPT ); Wed, 30 Jun 2021 21:51:20 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CA17F61466; Thu, 1 Jul 2021 01:48:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1625104129; bh=N1LQqUiDSomKhABEtMR/OUZHtMe9w8viZXVhfQJPVQE=; h=Date:From:To:Subject:In-Reply-To:From; b=YAvyqLJnC/cTWxtwxWig2iDPEvC1JrEZAqvKkEvChT006g6EAm9phO+Q0eHkldYUY blrUqV9sohddGRIzw3cPUzB/AKbii9DiXl5m2RgF+SFUqCkyM50sBXDFm5Is72FnYE TaH+n1QDuc2qWTRyr1jnlJ1uCyxUwWQXGs+7GJtw= Date: Wed, 30 Jun 2021 18:48:48 -0700 From: Andrew Morton To: aarcange@redhat.com, akpm@linux-foundation.org, almasrymina@google.com, axelrasmussen@google.com, bgeffon@google.com, dgilbert@redhat.com, hughd@google.com, jglisse@redhat.com, joe@perches.com, kirill@shutemov.name, linux-mm@kvack.org, lokeshgidra@google.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, oupton@google.com, peterx@redhat.com, rppt@linux.vnet.ibm.com, sfr@canb.auug.org.au, shli@fb.com, shuah@kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, wangqing@vivo.com Subject: [patch 032/192] userfaultfd/selftests: dropping VERIFY check in locking_thread Message-ID: <20210701014848.i6f-Ezd9w%akpm@linux-foundation.org> In-Reply-To: <20210630184624.9ca1937310b0dd5ce66b30e7@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Peter Xu Subject: userfaultfd/selftests: dropping VERIFY check in locking_thread It tries to check against all zeros and looped for quite a few times. However after that we'll verify the same page with count_verify, while count_verify can never be zero. So it means if it's a zero page we'll detect it anyways with below code. There's yet another place we conditionally check the fault flag - just do it unconditionally. Link: https://lkml.kernel.org/r/20210412232753.1012412-4-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Axel Rasmussen Cc: Alexander Viro Cc: Andrea Arcangeli Cc: Brian Geffon Cc: "Dr . David Alan Gilbert" Cc: Hugh Dickins Cc: Jerome Glisse Cc: Joe Perches Cc: Kirill A. Shutemov Cc: Lokesh Gidra Cc: Mike Kravetz Cc: Mike Rapoport Cc: Mina Almasry Cc: Oliver Upton Cc: Shaohua Li Cc: Shuah Khan Cc: Stephen Rothwell Cc: Wang Qing Signed-off-by: Andrew Morton --- tools/testing/selftests/vm/userfaultfd.c | 55 --------------------- 1 file changed, 1 insertion(+), 54 deletions(-) --- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-dropping-verify-check-in-locking_thread +++ a/tools/testing/selftests/vm/userfaultfd.c @@ -430,58 +430,6 @@ static void *locking_thread(void *arg) } else page_nr += 1; page_nr %= nr_pages; - - if (bounces & BOUNCE_VERIFY) { - count = *area_count(area_dst, page_nr); - if (!count) { - fprintf(stderr, - "page_nr %lu wrong count %Lu %Lu\n", - page_nr, count, - count_verify[page_nr]); - exit(1); - } - - - /* - * We can't use bcmp (or memcmp) because that - * returns 0 erroneously if the memory is - * changing under it (even if the end of the - * page is never changing and always - * different). - */ -#if 1 - if (!my_bcmp(area_dst + page_nr * page_size, zeropage, - page_size)) { - fprintf(stderr, - "my_bcmp page_nr %lu wrong count %Lu %Lu\n", - page_nr, count, count_verify[page_nr]); - exit(1); - } -#else - unsigned long loops; - - loops = 0; - /* uncomment the below line to test with mutex */ - /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */ - while (!bcmp(area_dst + page_nr * page_size, zeropage, - page_size)) { - loops += 1; - if (loops > 10) - break; - } - /* uncomment below line to test with mutex */ - /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */ - if (loops) { - fprintf(stderr, - "page_nr %lu all zero thread %lu %p %lu\n", - page_nr, cpu, area_dst + page_nr * page_size, - loops); - if (loops > 10) - exit(1); - } -#endif - } - pthread_mutex_lock(area_mutex(area_dst, page_nr)); count = *area_count(area_dst, page_nr); if (count != count_verify[page_nr]) { @@ -613,8 +561,7 @@ static void uffd_handle_page_fault(struc stats->minor_faults++; } else { /* Missing page faults */ - if (bounces & BOUNCE_VERIFY && - msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) { + if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) { fprintf(stderr, "unexpected write fault\n"); exit(1); } _