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b=IWvfirzMniNwG13wiim+tYJvHHNqtjnwB2Xmhzc+Mxq+gEpjC4wppnhtyoJJdylan Ic4ev5sD2XcmD4ZWlCd62CYnEZ0mqdN9M+63U2bGlR10Rsm9iojPfERVlK6SRyeVbS poawOx/Z28W4YqEFCytBm9qhcKdLhK/7f/d10Af0= Date: Mon, 23 Mar 2026 15:39:41 -0700 From: Andrew Morton To: Chunyu Hu Cc: david@kernel.org, shuah@kernel.org, linux-mm@kvack.org, ljs@kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev Subject: Re: [PATCH v5 4/6] selftests/mm/vm_util: robust write_file() Message-Id: <20260323153941.289938dd9ced4dbb76ca7804@linux-foundation.org> In-Reply-To: <20260323151753.2576137-5-chuhu@redhat.com> References: <20260323151753.2576137-1-chuhu@redhat.com> <20260323151753.2576137-5-chuhu@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: g8ew7n3q9cxxfhkh4g4eaowdu8c6jd88 X-Rspamd-Queue-Id: A99E440009 X-Rspamd-Server: rspam09 X-HE-Tag: 1774305583-384403 X-HE-Meta: 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 yp2r9rSP YfhI7v8fR4VTbG/x2asjGwNRb53O03cEEV8XPSVKlc6wHkurINEZ9q1i9xrim4KZzAD0m1E/E9DjVD5Vx771VFBW27bQOb7NViTC2bT7TAXfO1ZLya4XJtQmU3CwRPm2Vy/xMruGFTiQ89bSLBuJg+vi5peYkohx0Od45+n5K1ln9uMmlSpw1CGdTOavFeVJWuxZxUuCWItGTS3cfu0JCqXLF+Yg4o+koESwBSRCS9WacjEKZ5rVCCbh+PApjgtxFOKPfCcVxhVckBiBn2D3ZzGFSkEpw9y+ZYw5Oi6wTR/ZgMj4XAy9JRH7k5TwuX0ZJGmG0p6fRvln69Rn3P3r/e81E+UpitBB3uNgTIdI2Vzg5AHr2+ol9O+Ys7A1FNS/xlivc Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 23 Mar 2026 23:17:51 +0800 Chunyu Hu wrote: > Add two more checks for buflen and numwritten. The buflen should be at > least one, otherwise the 'buflen - 1' could underflow and cause trouble. > The numwritten should be equal to 'buflen - 1'. The test will exit if > any of these conditions aren't met. > > Additionally, add more print information when a write failure occurs or > a truncated write happens, providing clearer diagnostics. > > ... > > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -769,6 +769,8 @@ void write_file(const char *path, const char *buf, size_t buflen) > { > int fd; > ssize_t numwritten; > + if (buflen < 1) > + ksft_exit_fail_msg("Incorrect buffer len: %zu\n", buflen); > > fd = open(path, O_WRONLY); > if (fd == -1) > @@ -777,5 +779,9 @@ void write_file(const char *path, const char *buf, size_t buflen) > numwritten = write(fd, buf, buflen - 1); > close(fd); > if (numwritten < 1) > - ksft_exit_fail_msg("Write failed\n"); > + ksft_exit_fail_msg("%s write(%s) failed: %s\n", path, buf, > + strerror(errno)); AI review (https://sashiko.dev/#/patchset/20260323151753.2576137-1-chuhu@redhat.com) points out that `errno' was overwritten by the close(). Maybe. Or maybe a successful close() leaves errno alone, dunno. Apart from that the comments appear fairly minor. Please lmk if you think we should proceed as-is. (I'm really trying to slow things down now - we have a *lot* of material and a few weeks of consolidation is needed. But selftests/ tend to get a pass, for obvious reasons)