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Tue, 12 May 2026 00:49:36 -0700 (PDT) Received: from vini ([2401:4900:8fc8:73c6:dda6:576b:fa0d:f68e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2baf1d3ffa0sm127554695ad.25.2026.05.12.00.49.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 00:49:35 -0700 (PDT) From: Vineet Agarwal To: akpm@linux-foundation.org Cc: david@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Vineet Agarwal Subject: [PATCH] selftests/mm: check file initialization writes in split_huge_page_test Date: Tue, 12 May 2026 13:19:24 +0530 Message-ID: <20260512074924.27721-1-agarwal.vineet2006@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit create_pagecache_thp_and_fd() fills the backing file for the pagecache THP tests using repeated write() calls, but the return value is never checked. If a write fails or completes only partially, the test may continue with an incompletely initialized file and produce misleading results. Check the result of write() and fail the test if the expected number of bytes was not written. Signed-off-by: Vineet Agarwal --- tools/testing/selftests/mm/split_huge_page_test.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c index 500d07c4938b..eab69b0f59a0 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -609,9 +609,16 @@ static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, assert(fd_size % sizeof(buf) == 0); for (i = 0; i < sizeof(buf); i++) buf[i] = (unsigned char)i; - for (i = 0; i < fd_size; i += sizeof(buf)) - write(*fd, buf, sizeof(buf)); - + for (i = 0; i < fd_size; i += sizeof(buf)) { + ssize_t written; + + written = write(*fd, buf, sizeof(buf)); + if (written != sizeof(buf)) { + ksft_perror("write testfile"); + close(*fd); + goto err_out_unlink; + } + } close(*fd); sync(); *fd = open("/proc/sys/vm/drop_caches", O_WRONLY); -- 2.54.0