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 2AB3A277C96; Mon, 4 May 2026 07:35:54 +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=1777880155; cv=none; b=aaQJEY3y8iwlFq+u8NelZQf9uVXGVm6CULKd97My/hEzITtU5Ujm5GQKD47P5YgRug/H0EwInbEFEmVQwObuvRirzAgNIfjWbmxpc1fCthSZh0QsFvyCB4QtDn66r/r1jwi5VHIH1Tc2WZmVCCLtmtds0l2MyuoFqTu9SLIM0+8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777880155; c=relaxed/simple; bh=nP0S2q1CAzOGhGSdSCjymgPf8nuBERecQ5nTjVW12qQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iIt05MYng82nUGXofKIZfo6BwK5O8seS62zh7r1A7JIaeCdoqO0w1C8ksGsHhnRA8Ggj+qucFYZJBS/dWaaZJNT6H6J2bR60L+JnoCgB/QSvlXuJMP+A/pyqKfZdkgG8qU7OTK5PUZVtSOBPlE6MppqsXTipZJ1GSRua1A5mb1M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dwZxMQof; 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="dwZxMQof" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A297C2BCB8; Mon, 4 May 2026 07:35:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777880154; bh=nP0S2q1CAzOGhGSdSCjymgPf8nuBERecQ5nTjVW12qQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dwZxMQofx6uIXs7HGoHMgLNnUGRsmZWDDIiSADIemxTxLuZR8dhs4m4Bm9V0M2ioC z9kh24iWzmu55tMpnz7mCGxGsauMwJA1S+Ng/0/wRxsyZGVh6PJKThcrdJGRAkj9SV rL3AEJobAm+7b1ZdQRrXC+dhzIyqhYS+3dnPcmt5zlcfylov7Ke5LhFg40bbEK5qO/ zWF7IzrUBYNzg/seZaKvUhvg79C1U7uucNC8j+BrdpDntWlcohZNncxAeK49w4kV1u P+nW4+1+ARQpeoKBJTlnt8b0tIZVM41k2c94GuXsqiT4GB4xrNQIoURJbez270BpXA eU5lJh9mEJuMw== Date: Mon, 4 May 2026 09:35:47 +0200 From: Mike Rapoport To: Vineet Agarwal Cc: shuah@kernel.org, akpm@linux-foundation.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, surenb@google.com, mhocko@suse.com Subject: Re: [PATCH v3] selftests/mm: ksm-functional-tests: fix partial write handling Message-ID: References: <20260503101229.654763-1-agarwal.vineet2006@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260503101229.654763-1-agarwal.vineet2006@gmail.com> Hi, On Sun, May 03, 2026 at 03:38:40PM +0530, Vineet Agarwal wrote: > Update write() checks to properly detect and handle partial writes. > > Previously, partial writes (ret > 0 && ret != len) could be treated > as success because write() does not set errno in this case and the > code returned -errno. This could result in returning 0 and > incorrectly signaling success. > > Fix this by verifying that write() returns the full expected length > and treating any mismatch as failure. > > Signed-off-by: Vineet Agarwal > > Changes in v3: > - Simplify error handling as suggested by reviewer > - Return -1 when write() does not complete fully > - Rebase patch against base tree > --- > .../selftests/mm/ksm_functional_tests.c | 27 +++++++++++++------ > 1 file changed, 19 insertions(+), 8 deletions(-) > > diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c > index 8d874c4754f3..4abd98be3f59 100644 > --- a/tools/testing/selftests/mm/ksm_functional_tests.c > +++ b/tools/testing/selftests/mm/ksm_functional_tests.c > @@ -498,6 +498,8 @@ static void test_prctl_fork(void) > static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) > { > int ksm_fd; > + ssize_t ret; > + size_t len, sleep_len; ret and len should be of the same type and one len variable is enough. > ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); > if (ksm_fd < 0) > @@ -506,11 +508,17 @@ static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) > if (write(ksm_fd, "1", 1) != 1) > return -errno; > > - if (write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)) <= 0) > - return -errno; > + len = strlen(pages_to_scan); > > - if (write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0) > - return -errno; > + ret = write(pages_to_scan_fd, pages_to_scan, len); if (write(pages_to_scan_fd, pages_to_scan, len) != len) return -1; would be enough here and below. > + if (ret != len) > + return -1; > + -- Sincerely yours, Mike.