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 5DF6433ADB9; Tue, 28 Apr 2026 08:04:35 +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=1777363475; cv=none; b=ue0y+DS8P5NUh1DYVRPcgO0pt8cIqXWG9sD7GMTs7FuI+WH5r0hHNJ/vi5CZ6N9e53+qL0bN/aEp8ng0FOf+ay5lalFSEGRy4tsS+ShKYmk5ZBexeCn5S3dD+myFwYN1x1y0QF7k2x+IIYxJJed5RQQ5Z8Spnh2T6Q/NPbEnyWw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777363475; c=relaxed/simple; bh=NtmIbjTbL8hS7vDBEGYOIeztzGgTPC9MZsx2eECcozo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W3vt1b72zEq7Ae6GLa2bn9mqQnsaYz3P760+mMKxxMWm9Kemc0dteMdlHD3coMViUZbyMqHwZyV/YV8t8EhW1JkcWIrcSvTTnzXxi1MHl7cF6aGKzu0K7S5zMmOItnMOjIWceMwSw07wwmtR7LFPDz9P3djumQknKlkr2/3gpzg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XppfAnHz; 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="XppfAnHz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4168C2BCAF; Tue, 28 Apr 2026 08:04:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777363475; bh=NtmIbjTbL8hS7vDBEGYOIeztzGgTPC9MZsx2eECcozo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=XppfAnHz8MngFNTO2myVmeJ9/Oj2+/bCYRyj4mB900QrbG+dlkM5fWAW8Fg13lzUj PFpSAXHkl5PUM9jVWjIVQ/MnIrvHJQUo3zhAj8FPw370qIkBr6xC017NzJoYajllmH LXefxywCZ+Gsuff+chuFLBSjkY4RokZ8ARycGMnSz5pfHkvFz5zIRpIUHxVFJtmp9q nb/hEpovJGyhAXWSQp8/gaVDZYE+nkvnV2pJlZHBnIt04rz4A2tQ8jsGorQgQc1lw2 /oyaMaQkDXhkcv8A4mh0Ws8wysE3wRfGaE8BL1nraNFpdSGhH/JckeHzO78cYx0Ta9 x56ZMyQqzSYUg== Message-ID: <3abf09d8-a98e-4f1b-b8d9-77879a8a2733@kernel.org> Date: Tue, 28 Apr 2026 10:04:30 +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] selftests/mm: khugepaged: handle partial write in file_setup_area() 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: <20260428062322.20417-1-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 08:23, Vineet Agarwal wrote: > file_setup_area() writes initialized test data into the backing > file used for collapse testing, but it ignores the return value > from write(). > > If write() fails or completes only partially, the test continues > with incomplete file contents, which can lead to incorrect test > results and make failures harder to diagnose. > > Handle partial writes by retrying until all data is written and > abort the test if write() fails. > > Signed-off-by: Vineet Agarwal > --- > tools/testing/selftests/mm/khugepaged.c | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > index 3fe7ef04ac62..c13f06758750 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -369,7 +369,9 @@ static void *file_setup_area(int nr_hpages) > int fd; > void *p; > unsigned long size; > - > + size_t remaining; > + ssize_t ret; > + char *buf; > unlink(finfo.path); /* Cleanup from previous failed tests */ > printf("Creating %s for collapse%s...", finfo.path, > finfo.type == VMA_SHMEM ? " (tmpfs)" : ""); > @@ -383,7 +385,19 @@ static void *file_setup_area(int nr_hpages) > size = nr_hpages * hpage_pmd_size; > p = alloc_mapping(nr_hpages); > fill_memory(p, 0, size); > - write(fd, p, size); > + remaining = size; > + buf = p; > + > + while (remaining > 0) { > + ret = write(fd, buf, remaining); > + if (ret <= 0) { > + close(fd); > + munmap(p, size); > + ksft_exit_fail_msg("write() failed while preparing test file\n"); > + } > + buf += ret; > + remaining -= ret; > + } Why are we even using write() instead of just mapping the fd and writing to that area? diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 3fe7ef04ac62..a77f753ccf38 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -381,9 +381,10 @@ static void *file_setup_area(int nr_hpages) } size = nr_hpages * hpage_pmd_size; - p = alloc_mapping(nr_hpages); + p = mmap(BASE_ADDR, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + if (p != BASE_ADDR) + ksft_exit_fail_msg("mmap() failed while preparing test file\n"); fill_memory(p, 0, size); - write(fd, p, size); close(fd); munmap(p, size); success("OK"); -- Cheers, David