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b=KYYWJjGiP1IhaBTL9bzl4SUN0sICrsu2ysruF90aeyyhhHe091gB5ZizvbYp3LnLL UjV4PdcbPG/Yr4eLiZktqgjNm24coo+DahqxifQ4t+Rb1l9hKzKNrur/thllz/1sX/ EOmZrClBvNoKSNFXdklaXlH6RIEe7cSV0vMTAp9EG+wF9HEQCrOJC4tsOOS/uYbrmX 3NlIrnlJPcRM0kRhEX0ouAl0e/Oqo7IwwhrOqWjP5D9h6j7CGNprtoeRlRRJ+igLI4 UdS1Sg4V19ERBRCmUui27c8SbCKk/aQtkmAqDMXfP+OgL7zEbNbl+uzu10PNLlvLBd 7KKk2s4p4MxhA== Date: Tue, 7 Apr 2026 11:55:55 +0100 From: Lorenzo Stoakes 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 v8 4/6] selftests/mm/vm_util: robust write_file() Message-ID: References: <20260402014543.1671131-1-chuhu@redhat.com> <20260402014543.1671131-5-chuhu@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260402014543.1671131-5-chuhu@redhat.com> X-Rspamd-Queue-Id: E6E951A0003 X-Stat-Signature: nnhbqawroktid7cqd1po6ctr1mqapzke X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775559362-367203 X-HE-Meta: U2FsdGVkX1/ymahz+TT9NFzsOu089y8tUKhUlUwHI82fX0jeXIOgdpcRnRLLhTf5/wScg0e79fMkcLk7bFFdaCgbx0TOFsuPQYHzRGRuY6KAektsdb+mfg8/CxzjlQC6YLlE9k1KgnSjPLsnfWPFj+zMSn0lrhi3VoLt1hYdJ4ycG/q/sXZ1JUBnm8YckFKr4jCRlaujbozl2BgYiFyJqomMftbNeIVmz3GxQYxVM5/Dyhg8B/GcKhr0Dya3VT8nUb9zHCL79/CIVrqvquvCF6ybJD4skWAjbJCguX4BPjtnvLkuGcC0/qmqA63PBAKisbaIFkVNtp4A6fIRCJ/53TBQ8SiZDmvqWmGWW4bEdAv5ZkIkW7h0IMysGn86uae2kitne3L/tW273zPV46oI+Fgk9cjVrdnRy4raR6c4S1CLDeO641zewCJhMoW+7YTTRX2/3xK6rYmm4RXLSgaG3AzOMnW8QTY4myTW4/r6drj4D1vCVpllZC3zXncJbwQ7Xqlz7JsV3CLtSTXYfEDv7uDN8Tgsqpyg6Q1NDHymPSt78D7aVQeAGZT2FerRfT5YETFYlRZKbc3hHWGkHpfhe5PxgTvvQtZ1xYaOiq++xI/7s6AlT5G63t6npuxMbaPZUAiACnoHYt1mUmy8ERyXkBM1B1qUDAzxuAjaR8YKg1COG9hFvSw/tUEDHsiWG5X4NE9lKjqo8auwWp/jAm07LcCaLP2EqxV3nrNy0qZ+ET+sTXEAsb7yX+Vt0I3twSYxku7Qs4UQG5Bm9qW8qdzsP/s2Etwq61ogz81DiBkM+VWMa+hMbePFShjqSulj7a3XRCf+XRYIogACP/+HTrx/ur/UlDMK1dLDZRuNU61toDCzptJxj664pT93o4hYmhq5B4L5yUN2w1Ffr8rjL48b8zy/xMPL21NpBcRGRnta6fG0DTcWNTtgw0ne4x9aKrMZCLRFMDnV+r+Lfi6aCsg VksSpWIa 0MPC9ychWsnd+Ox0p7RrhopjCiGumoZEJokNnZ5zlf30l2C+zDa9tudf+GO8mB5hnLBTJfKyb9n2D8ppvRwpSTozO56xb8CWJ1HuTuFCnnzoOih62Rn4o0iLKa4C9j744YeAvqRhIiubBHKECOgUJ1SihBVFWvMlKEFAU7DdsjesBFEPkByNX0QmhBLqckTkct1c71KBopMw+Y//+KfkNwzbgdizz/BiWsR3I7rhUOvRlwkAyZfmQsS3wgaQo8ZJCqF0EuOdGZiydmU2HwmVlp6maeFHrw+7aWTmroU7JCLD3joQlDAaWspowaL72KXt2KFxUxEK4Tel6nn8vi203qI1KPfvaDTLADTZV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 02, 2026 at 09:45:41AM +0800, Chunyu Hu wrote: > Add three more checks for buflen and numwritten. The buflen should be at > least two, that means at least one char and the null-end. The error case > check is added by checking numwriten < 0 instead of numwritten < 1. And the > truncate case is checked. 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 LGTM, so: Reviewed-by: Lorenzo Stoakes > --- > Changes in v8: > - go back to ksft_exit_fail_msg in the two error exit path as no clean > ksft_exit_fail_perror that supports va_list > Changes in v7: > - add an empty line before the 'buflen < 1' line. And change to > 'buflen < 2 to limit the buflen at least to be 2, so at least one char > is allowed. > - handle the numwriten < 0 case, which is the error path. > - use ksft_exit_fail_perror in error exit path. > - use %.*s to print the buf when error happened > 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 | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index ad96d19d1b85..db94564f4431 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -767,15 +767,24 @@ 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 < 2) > + 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); > - if (numwritten < 1) > - ksft_exit_fail_msg("Write failed\n"); > + errno = saved_errno; > + if (numwritten < 0) > + ksft_exit_fail_msg("%s write(%.*s) failed: %s\n", path, (int)(buflen - 1), > + buf, strerror(errno)); > + if (numwritten != buflen - 1) > + ksft_exit_fail_msg("%s write(%.*s) is truncated, expected %zu bytes, got %zd bytes\n", > + path, (int)(buflen - 1), buf, buflen - 1, numwritten); > } > -- > 2.53.0 >