From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 0280C3D7D6F; Tue, 28 Apr 2026 09:46:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777369614; cv=none; b=e8qyYd2qVp2zFS/tUJt6uDABah1wSikmF13IWT6H25vdFFsn/F1wWqPgMWVKKzme5tiD7uwCn5Y8+mCVVBrAcnowe5jKX3i1fgSUIOIXvXIownILPVEojoFZ9IqQJhj9xGbcsrvKFCD/5C2GYyBvXyBfuj5XH/A8FPXIvTfeKrw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777369614; c=relaxed/simple; bh=NuCzlS/M+0qb9wYmyxAdJZ1X0Ei1vmHAzLdDPlKd0yU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AgIzYTRYFInBf8bFGfr5zoJO/HGdIfECl86O0uTOHvapeI1EBA6WU+jfw/RPFWosrmyyWqBzOyNTFa2cuR+zJsJKoOIZAxyelbunFaGtooxgAuH8hv9X75aY2e5WOV7IIYoHEevhqgeureH3zj9mRRWVtPLns1d/a/+fuOoIsYk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MjcSMSxs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MjcSMSxs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F83FC2BCAF; Tue, 28 Apr 2026 09:46:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777369613; bh=NuCzlS/M+0qb9wYmyxAdJZ1X0Ei1vmHAzLdDPlKd0yU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MjcSMSxsedoT4NYhHO4hgQYknMa2fzyOyKGwVmjwecRlEcx7oBgR5fGxGFgqH81XX QSjJRaPMlET2l4yyLaXwP+hbLXftS0dJZCWO6wzW85RXD9eWOYsNaiu8Dz1D5+EA60 utpi0XZfQJOC9FNp8gK6LB6pevLsLde5Y8JtfloNAXp5h3esC4gsA4vT1ZkzT9BW44 pWaIR23pVlUrgodkQDPPpfyfjMlw6jZI/P7s4hQofiCeVKAWZBWOWM3u2vch4+NYLj gNHsKdHUJ6eGyi7a5AclBwYc5PqlvsQnZcs7vdFYouvwVXYHYHn4NRfqRHX+ep6fk3 mOGTiMv+hF/Hw== Message-ID: <548dc617-ca19-45f6-852f-adebcf8d3a11@kernel.org> Date: Tue, 28 Apr 2026 11:46:48 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] selftests/mm: khugepaged: initialize file contents via mmap To: Vineet Agarwal , akpm@linux-foundation.org, ljs@kernel.org, shuah@kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <3abf09d8-a98e-4f1b-b8d9-77879a8a2733@kernel.org> <20260428094356.60415-1-agarwal.vineet2006@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/28/26 11:43, Vineet Agarwal wrote: > file_setup_area() currently allocates anonymous memory, fills it, > and writes it into the backing file used for collapse testing. > > Instead of copying data through write(), map the file directly with > MAP_SHARED after resizing it with ftruncate(), initialize the mapped > area in place, and sync it with msync(). > > This simplifies the setup path and avoids the need for explicit > partial write handling. > > Signed-off-by: Vineet Agarwal > --- > tools/testing/selftests/mm/khugepaged.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > index 3fe7ef04ac62..f6e171e1da4f 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -369,7 +369,6 @@ static void *file_setup_area(int nr_hpages) > int fd; > void *p; > unsigned long size; > - > unlink(finfo.path); /* Cleanup from previous failed tests */ > printf("Creating %s for collapse%s...", finfo.path, > finfo.type == VMA_SHMEM ? " (tmpfs)" : ""); > @@ -381,11 +380,29 @@ static void *file_setup_area(int nr_hpages) > } > > size = nr_hpages * hpage_pmd_size; > - p = alloc_mapping(nr_hpages); > + if (ftruncate(fd, size)) { > + perror("ftruncate()"); > + close(fd); > + exit(EXIT_FAILURE); > + } Why is that required? We write all pages. > + p = mmap(BASE_ADDR, size, PROT_READ | PROT_WRITE, > + MAP_SHARED, fd, 0); > + if (p == MAP_FAILED || p != BASE_ADDR) { > + perror("mmap()"); > + close(fd); > + exit(EXIT_FAILURE); > + } > fill_memory(p, 0, size); > - write(fd, p, size); > - close(fd); > + > + if (msync(p, size, MS_SYNC)) { > + perror("msync()"); > + munmap(p, size); > + close(fd); > + exit(EXIT_FAILURE); Why is that required? -- Cheers, David