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 0E7B01FECAB; Wed, 29 Apr 2026 06:24:10 +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=1777443851; cv=none; b=MmTAdeK2VTXZDqF9x3WFnnf/uYW8kvJQbOga/lBn+vJ7UthCcjeXZ6JcKvR41oZSkYiL3hk0tJZssOSKpPNtDJp9uDOQngbGv3g/ondlaMGpohj3IYZjaY8cvZElQmAlq5o8Q134uUtUI7YxY027ZFaVIgQAA8miFR4kiPC9kxo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777443851; c=relaxed/simple; bh=s+ymMav/zVV2SJ+TT8pbk15gl8mNj7o6Akyk3HmVUfs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mL6jhUGTBEZ643kqD7tYUXcPfMvjDv5TsP+3n+DwHxGYFPCY4ziiEn6RfTkAJnrhzNLkPnh/7S29LqO1s58CX0MMlxnzGi9h8aPTMoYwv0/wM6aYvEAHC979A7c0BnafGFsON2S5yqMVLfzUkdil4iFOW1tBp9EsTigx0CavwqY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l1AF5oK/; 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="l1AF5oK/" 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 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 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 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