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imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="l1AF5oK/"; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777443851; a=rsa-sha256; cv=none; b=2YzAGlTrCBbZIbIQtf9PTZMOMnA8KiddrFfbq70vITjWAZnaLQ1xmbnUHnAwtgz5kbHmir QFBZo+BTjAwms3JRHOKfdqOljspjzHdRWWYuJP+QXxXJp4ZJb6+l0i2eLRcnbMQMDPRSeL /BiqtiWAN8lZg+mo/J365LuygselKwI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id F348160018; Wed, 29 Apr 2026 06:24:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2DFC8C19425; Wed, 29 Apr 2026 06:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777443850; bh=s+ymMav/zVV2SJ+TT8pbk15gl8mNj7o6Akyk3HmVUfs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=l1AF5oK/Ad1oKm+XDPVJGXhbnsF6R/VJ6vaENlzRCqrRU1VLmBozvcWGa4mmif8T1 mNtmvsN+ZRHdbXq6CwaEcpT9hdZ8RSL7Iht1u+iLrZYUszoZHZ980Qdmx098gdV4xe nEsRGS7lGiZ3ICaIvBFe+UOJYsF2BWe2S4wPiE8NzUmxm9m9/D7VQsApcMsyDqKPWm fdWQeclN/77TgkMlp/zJDa+fyETJGhDeXI+7cU2Gp+9260l0CcK1v9INgvtrmObUW5 r0rv3KpqTvm9KY4afKXCsWnGSVW7Et3KioIZbvBewJt6f66oFu6BH/JGzLPZcN5Ia1 CUWSjw2HqiHTA== Message-ID: <1c8a5cf4-e6e0-40da-b1e9-83f41a8b3f7a@kernel.org> Date: Wed, 29 Apr 2026 08:24:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] selftests/mm: khugepaged: initialize file contents via mmap To: Zi Yan Cc: Vineet Agarwal , akpm@linux-foundation.org, ljs@kernel.org, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260428133138.88802-1-agarwal.vineet2006@gmail.com> <583F8EE1-5C49-4250-A24B-0D73372E3864@nvidia.com> <95714cec-205e-4b56-b8ff-9afaf9408020@kernel.org> <0FA813EA-5EFA-482F-B8BF-FE65D4169C44@nvidia.com> <83EFF919-7A84-4773-8C16-C51C15C3D987@nvidia.com> <8D71AC0C-A10D-4B1E-B5B9-606422E0B99B@nvidia.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 X-Stat-Signature: 1wj6qkt7hqmpei7md8bmjdrogrhqsfyg X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A37F2180003 X-Rspam-User: X-HE-Tag: 1777443851-960850 X-HE-Meta: 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 SvxfMBPG iOvofPPBD0O2BUNC3iUYiKyGaRTIb4+ZQpMircO4aEJfD6b1Wr5C2yzQCd79RmoA1OZUkpCzuh3ylxw4ogEdwQ2XFRPpNDlLinzVvvAjYHihx1w1FlBG+3vtSKAY2ya9P5Qw94p9Y15/oSo6UKAdmt+Y0jB2OE4bt6IOpoqrxuK9EPl3IY/f4w8xOxhPbxC3n2IUGJXfquLMrXp+gzWpW4aqaRtV/thpkqq/skIcoHeLKoVk9LLNvDKX2HWpYytJWkVEppaDlE4OjW/7umwqOmMcYWkmPqf1PNGr81ASbCVxu2pVoJMkRJHo0xHiqszqJfBN0havzAAPZf/g= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/28/26 22:23, Zi Yan wrote: > On 28 Apr 2026, at 16:22, Zi Yan wrote: > >> On 28 Apr 2026, at 16:19, David Hildenbrand (Arm) wrote: >> >>> >>> But why doesn't the write() make the folios dirty? Or are we running into some >>> race condition where the old code just worked by chance? >>> >> >> The fd is opened with O_DSYNC, so the data from write() is transferred to >> disk when write() returns. > > And the folio is clean. Ah, I missed the O_DSYNC. That makes sense, thanks. v2 actually contained the msync. So I assume we could then drop the O_DSYNC. Note: there is no need to close the file or munmap before the exit on the error path. The following works for me diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 3fe7ef04ac62..5862a3213840 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -373,7 +373,7 @@ static void *file_setup_area(int nr_hpages) unlink(finfo.path); /* Cleanup from previous failed tests */ printf("Creating %s for collapse%s...", finfo.path, finfo.type == VMA_SHMEM ? " (tmpfs)" : ""); - fd = open(finfo.path, O_DSYNC | O_CREAT | O_RDWR | O_TRUNC | O_EXCL, + fd = open(finfo.path, O_CREAT | O_RDWR | O_TRUNC | O_EXCL, 777); if (fd < 0) { perror("open()"); @@ -381,9 +381,21 @@ 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()"); + exit(EXIT_FAILURE); + } + p = mmap(BASE_ADDR, size, PROT_READ | PROT_WRITE, + MAP_SHARED, fd, 0); + if (p != BASE_ADDR) { + perror("mmap()"); + exit(EXIT_FAILURE); + } fill_memory(p, 0, size); - write(fd, p, size); + if (msync(p, size, MS_SYNC)) { + perror("msync()"); + exit(EXIT_FAILURE); + } close(fd); munmap(p, size); success("OK"); -- Cheers, David