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b=RoYYMi8yUVIC6LABKdz3pZSOFlH7vKHjWuAzDmYtIAEtwsmXnmnFpjCd8kfwiJytN Yg9AQsASr8iS2v7eKjKFJ/PmbgrP0wCGmjMTh2rDHikOKg9XlKrV80aMT8KV9qIVos b/AGqUX/6Gj3nvyE3iuxv44oLw802LOad1epym3BeDL0xS4+m8BXH2z0XI2JrdGQ6U OClGvfduAlQBAsGY89etD+SjLcb9vZ3StCJc2yvfNStA99kxD+SgHViiR0HOkuozmF Yf12ZNT7RGzAVubbu6NPP9brH1WBMjvsE2zGceo+foOIOfft8CtA2OH4TrKb9X5wLO XMjT6RvTI3B2Q== Date: Fri, 27 Mar 2026 07:46:03 +0000 From: "Lorenzo Stoakes (Oracle)" To: Chunyu Hu Cc: akpm@linux-foundation.org, david@kernel.org, shuah@kernel.org, linux-mm@kvack.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 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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: AD7D920009 X-Stat-Signature: peow6toibs5ycn84h7iu9g7krzzuoim9 X-Rspam-User: X-HE-Tag: 1774597571-72223 X-HE-Meta: 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 Ig/rBqWM AcS6ml83afwz8COSXPx+CXf8Ew3axgX6MzM59BdHeYiw+y50IsDD8bY0il3PLGQBq4hqcy8B3kDf3YitQWK218F78ZiDyEzRefaD9W8x5zzOJW0Rv+z8OZeltHbt0jV7dTvzebvQUaGIfPA29alIwIGIPZNB6jTMY/2F394h17G4rmYzk0dSQzimNfC53YlJVh7wmIhsGRIO8dmqXeUomerOwAPJrkRDPKKzgw/CqICdLGZhNWkFxrExAzQG2BhN7x7YXrd4PL/O3PVDeMSNx5rWclPmHz9ejamPC 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) As per Sashiko (presumably didn't look :P), let's make this < 2 since we write buflen - 1 bytes below which we don't ever want to be 0. > + 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)); > > 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)); > + 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 >