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[174.93.75.154]) by smtp.gmail.com with ESMTPSA id y29sm8958925qtm.13.2021.04.12.16.27.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Apr 2021 16:27:59 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrea Arcangeli , peterx@redhat.com, Andrew Morton , Mike Rapoport , Axel Rasmussen Subject: [PATCH v2 3/5] userfaultfd/selftests: Dropping VERIFY check in locking_thread Date: Mon, 12 Apr 2021 19:27:51 -0400 Message-Id: <20210412232753.1012412-4-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210412232753.1012412-1-peterx@redhat.com> References: <20210412232753.1012412-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Reviewed-by: Axel Rasmussen Signed-off-by: Peter Xu --- tools/testing/selftests/vm/userfaultfd.c | 55 +----------------------- 1 file changed, 1 insertion(+), 54 deletions(-) diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c index 5cae66e27171..387b9360ae64 100644 --- a/tools/testing/selftests/vm/userfaultfd.c +++ b/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(struct uffd_msg *msg, 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); } -- 2.26.2