From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752247AbbIOMKx (ORCPT ); Tue, 15 Sep 2015 08:10:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59283 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785AbbIOMKw (ORCPT ); Tue, 15 Sep 2015 08:10:52 -0400 From: Vitaly Kuznetsov To: Andy Shevchenko Cc: Rasmus Villemoes , Andrew Morton , James Bottomley , linux-kernel@vger.kernel.org, "K. Y. Srinivasan" Subject: Re: [PATCH v3 2/2] lib/test-string_helpers.c: add string_get_size() tests References: <1442249150-31650-1-git-send-email-vkuznets@redhat.com> <1442249150-31650-3-git-send-email-vkuznets@redhat.com> <87y4g8wtjo.fsf@rasmusvillemoes.dk> <1442299382.8361.25.camel@linux.intel.com> Date: Tue, 15 Sep 2015 14:10:43 +0200 In-Reply-To: <1442299382.8361.25.camel@linux.intel.com> (Andy Shevchenko's message of "Tue, 15 Sep 2015 09:43:02 +0300") Message-ID: <87wpvryjb0.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Shevchenko writes: > On Tue, 2015-09-15 at 00:00 +0200, Rasmus Villemoes wrote: >> On Mon, Sep 14 2015, Vitaly Kuznetsov wrote: >> > > Vitaly, thanks for the test cases. My comments below. > >> > +static __init void test_string_get_size_one(u64 size, u64 >> > blk_size, >> > + const enum >> > string_size_units units, >> > + const char >> > *exp_result) >> > +{ >> > + char buf[256]; >> > + >> > + string_get_size(size, blk_size, units, buf, sizeof(buf)); >> > + if (!strncmp(buf, exp_result, min(sizeof(buf), >> > strlen(exp_result)))) >> > + return; >> >> Nits: It probably makes sense to also test that string_get_size >> '\0'-terminates the buffer, so I'd spell this >> >> if (!memcmp(buf, exp_result, min(sizeof(buf), >> strlen(exp_result)+1))) >> >> With a generous stack buffer, that min() will always evaluate to the >> strlen(exp_result)+1. On that note: Maybe 256 is a bit excessive. I >> don't think this will run very deep in the kernel stack, but the code >> might >> get copy-pasted somewhere else. 16 should be plenty. > > Agree with Rasmus. > > And just to make a side note that useless use of min() since we have > strnlen() :-) > >> >> > + pr_warn("Test 'test_string_get_size_one' failed!\n"); >> > + pr_warn("string_get_size(size = %llu, blk_size = %llu, >> > units = %d\n", >> > + size, blk_size, units); >> >> [There's probably no pretty way of getting from units to a text >> representation, but it's slightly annoying to have to check the >> source >> for the enum definition to figure out what units=0 or units=1 means.] >> >> > + pr_warn("expected: %s, got %s\n", exp_result, buf); >> >> In case we failed to '\0'-terminate buf, we might want to print it >> with >> "%.*s", (int)sizeof(buf), buf. But maybe I'm just overly paranoid. > > I prefer to put '\0' at the position after we expected have an actual > '\0'. In this case we always be NULL terminated. I did this for hexdump > test cases. Just to check I got your suggestions right: ... + if (!memcmp(buf, exp_result, strnlen(exp_result, sizeof(buf) - 1) + 1)) + return; + + /* NULL terminate buf right after the expected '\0' */ + buf[strnlen(exp_result, sizeof(buf) - 2) + 1] = '\0'; ... Alternatively, we could have avoided strnlen() by asserting strlen(exp_result) < sizeof(buf) - 1 at the very beginning. -- Vitaly