From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1528D2F3C30; Tue, 16 Dec 2025 14:57:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765897024; cv=none; b=rdg2aP6P7NitShDsUK6dWPuIWiohQhnCVYBUU2FlUEzs3GdHf1jEMZ1xkmmcLfL+GmBs03vH7hFQQwv9gUQzsRhJxxzBlMZQwfxhTIwD5etm393XT/mkNEbfl2hthiYpVehEYCVC+qAKTJEBqycT9nxK2H7klaL+qUWg2CIypJc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765897024; c=relaxed/simple; bh=gw3zvtBVCTRX8RRdLjk8TzkpVg+pcEDv0JAIkJczZvI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=n7Iy+TMUeHdebPd0YjxrqVOSGz4N9fqmRn4drgaXHl6iWTBikb8T8QXm1hXMb677CChPHTbz4LA5MNvHjMX0VCtvZlkua86qF1iztewnvP2G++aSFEW4j3acRXmq+78Thjyo52OuQszgoica6QjXtH0ZjzbtSDUsA2XmHWqHUkQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3972DFEC; Tue, 16 Dec 2025 06:56:55 -0800 (PST) Received: from [10.57.91.77] (unknown [10.57.91.77]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 937B03F73B; Tue, 16 Dec 2025 06:57:00 -0800 (PST) Message-ID: <37210500-6f6e-46ac-ac2f-ac996308590d@arm.com> Date: Tue, 16 Dec 2025 14:56:58 +0000 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4] selftests/mm: fix faulting-in code in pagemap_ioctl test Content-Language: en-GB To: Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Mark Brown , Shuah Khan , Usama Anjum References: <20251216142633.2401447-1-kevin.brodsky@arm.com> <20251216142633.2401447-4-kevin.brodsky@arm.com> From: Ryan Roberts In-Reply-To: <20251216142633.2401447-4-kevin.brodsky@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/12/2025 14:26, Kevin Brodsky wrote: > One of the pagemap_ioctl tests attempts to fault in pages by > memcpy()'ing them to an unused buffer. This probably worked > originally, but since commit 46036188ea1f ("selftests/mm: build with > -O2") the compiler is free to optimise away that unused buffer and > the memcpy() with it. As a result there might not be any resident > page in the mapping and the test may fail. > > We don't need to copy all that memory anyway. Just fault in every > page by forcing the compiler to read the first byte. > > Cc: Usama Anjum > Signed-off-by: Kevin Brodsky > --- > tools/testing/selftests/mm/pagemap_ioctl.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c > index 2cb5441f29c7..67a7a3705604 100644 > --- a/tools/testing/selftests/mm/pagemap_ioctl.c > +++ b/tools/testing/selftests/mm/pagemap_ioctl.c > @@ -1056,7 +1056,6 @@ int sanity_tests(void) > struct page_region *vec; > char *mem, *fmem; > struct stat sbuf; > - char *tmp_buf; > > /* 1. wrong operation */ > mem_size = 10 * page_size; > @@ -1167,8 +1166,9 @@ int sanity_tests(void) > if (fmem == MAP_FAILED) > ksft_exit_fail_msg("error nomem %d %s\n", errno, strerror(errno)); > > - tmp_buf = malloc(sbuf.st_size); > - memcpy(tmp_buf, fmem, sbuf.st_size); > + /* Fault in every page by reading the first byte */ > + for (i = 0; i < sbuf.st_size; i += page_size) > + (void)*(volatile char *)(fmem + i); We have FORCE_READ() in vm_util.h for this. Perhaps that would be better? > > ret = pagemap_ioctl(fmem, sbuf.st_size, vec, vec_size, 0, 0, > 0, PAGEMAP_NON_WRITTEN_BITS, 0, PAGEMAP_NON_WRITTEN_BITS);