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b=gG3JNHS2r8tw4BAPgiCvkVDhREBhFMB72+fGe4fR9spd9APmORjZYd8Xb69ygI8JO 4vEKHENnLe/BZ+47FfQXurrgYhUzorJ2IXP2e2n77JPaOB+ncMOcOZce0c3Zaxe7NF 9VnkLGAdrbhEpLs5EwhyR5t2zLu7lNnKR1rbOEnAsrb6SVP6ZKWBBy3xy1ubR9xIF+ rSUUUPvqW05hB3S2125JudhUuiWmvna3jyeSasYilQmyLoSoVAxy8kxroqq6g9u/Ls nFVz+dcgo1JHgg7NhZ9OvZ0A2tD0Nb383uOlmdgyXfg2UuOejuCQ/knrq6K5KTRx+k 0yF06X7oAWONg== Date: Fri, 27 Mar 2026 15:32:01 +0300 From: Mike Rapoport To: Chunyu Hu Cc: akpm@linux-foundation.org, 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, 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 v6 4/6] selftests/mm/vm_util: robust write_file() Message-ID: References: <20260324013316.2590422-1-chuhu@redhat.com> <20260324013316.2590422-5-chuhu@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260324013316.2590422-5-chuhu@redhat.com> X-Rspam-User: X-Stat-Signature: jw4oasdh36qhzkaqsuiafb734koyr93r X-Rspamd-Queue-Id: CAF7EA0017 X-Rspamd-Server: rspam09 X-HE-Tag: 1774614731-636726 X-HE-Meta: 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 ngQF20zh NRwobp67/m5Iael1Ff/o4C433oe83pPqz0VOorAT1ujAwjyWfLx5RZvNQ9OwtV4kM3SKsQvXIze2sZ+O2Iw97e43fR5j9YNOY6minmw8/Ts9+HBlEWhnbn64F4uoa68WOh5fiNEd7hFWcDwo8ndOt3UMDNe3rfhLMdaNTZJuN2KcdMQHrTUBhuy47j3g84wV+KVCBxC3anp+/lCsmCg/UUITW613I5XNt5apin9ckFPCav4jlKCurdWzDEpKIyRYfo9ZuvyZx3pO4G5xRI/bZmfz7GojP95s3cWYSVjgXkJKXJABgoe8714GWUqN3xQXg4oxw492ldj/yIGA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 24, 2026 at 09:33:14AM +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. > > Signed-off-by: Chunyu Hu > --- > Changes in v6: > - save/restore errno before and after the close(), so the log could show > the correct error info on failure. Suggested by AI. > Chagnes in v5: > - new patch for making improve on write_file. Add more safety checks and > diagnostics info in log > --- > tools/testing/selftests/mm/vm_util.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index ad96d19d1b85..572ccb99de8e 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -767,15 +767,23 @@ int unpoison_memory(unsigned long pfn) > > void write_file(const char *path, const char *buf, size_t buflen) > { > - int fd; > + int fd, saved_errno; > ssize_t numwritten; > + if (buflen < 1) > + ksft_exit_fail_msg("Incorrect buffer len: %zu\n", buflen); > > fd = open(path, O_WRONLY); > if (fd == -1) > ksft_exit_fail_msg("%s open failed: %s\n", path, strerror(errno)); We have ksft_exit_fail_perror(), fits great here > > numwritten = write(fd, buf, buflen - 1); > + saved_errno = errno; > close(fd); > + errno = saved_errno; > if (numwritten < 1) > - ksft_exit_fail_msg("Write failed\n"); > + ksft_exit_fail_msg("%s write(%s) failed: %s\n", path, buf, > + strerror(errno)); and here. > + if (numwritten != buflen - 1) > + ksft_exit_fail_msg("%s write(%s) is truncated, expected %zu bytes, got %zd bytes\n", > + path, buf, buflen - 1, numwritten); > } > -- > 2.53.0 > -- Sincerely yours, Mike.