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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260503101229.654763-1-agarwal.vineet2006@gmail.com> X-Rspam-User: X-Rspamd-Queue-Id: B7E97A0002 X-Rspamd-Server: rspam04 X-Stat-Signature: 3drcsgutc5ugm7e8hb5n7fczmyatudgh X-HE-Tag: 1777880155-136092 X-HE-Meta: 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 OBp7y9JI X1BmX4kzlG/TnZ3UOWV19bUBY0ENpOoMs+JBu05WqYchoxQi267J+YZzHdeKsI3qlria0FhF4XnxyJYohjZOxpOENBOkqlHHiQkQ75/G2D7B2lynJusemnmgDTX/9jqRy6i6E8Eh5dZmHkOGNf5bfhdYFYIup3dmI1yWwdF3GUVytlmhQ5nhppVORjA+htB5iRQ9JlthmBIjSe1YcX2I3gmRQ8wO05vKRHsRkslQbzQwVGSnOB96w41IHCF4U8FZ2NIar1I3SrehAlX0k7TYpqPDNyHS0vI/VFGWEAh8p876t0noXuDrW4siIAT/IcchE+ByUVLgeKDvv0P5YmPxNYq1yCV48G4MQAHJ5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.