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b=tUmyORdZEQ4TsK52/wjbnKFD+Fd0KI4yTlM+aOVnDNkxtXohyUqkw9Dtee9cAcgxI FfqgRLwtmY6GapCsqEC7B1puBoDsFh+PiAcln75vRKNNfohE7/SQqRmC/53ea6rw9s CnJnQ0iGM10Bzul6b3+rU9/nKzJ5d/8ALwcF2Vsz91sLELC0EektvN8lBXwNXElfrE pFsyB0uGrS2YMvBBOf6U2aqildxygJ9c1QfzYES1KZfZVyDEEwklKNl6SLWWYnPU/M 28Yqq4qlpTo+xN1PGT9Do0ifF4/Ie2x3EuyK7aQf7e7CGDcjAtkUU8X3Jp8Wv0pDf6 RRuPos3tcY3tw== Message-ID: <3b853391-11b3-4cca-bfae-c8147a72231e@kernel.org> Date: Thu, 2 Apr 2026 10:05:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 4/6] selftests/mm/vm_util: robust write_file() To: Chunyu Hu , akpm@linux-foundation.org, shuah@kernel.org, linux-mm@kvack.org, ljs@kernel.org Cc: 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 References: <20260402014543.1671131-1-chuhu@redhat.com> <20260402014543.1671131-5-chuhu@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1788FC000C X-Stat-Signature: mma7bztr3m5jnirrmf4fe7rwigtpc1pk X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1775117143-394586 X-HE-Meta: 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 cSr/jDbV 4D4UMkB4Y1ARajEhzzZlQVo7aZC7kq5weu1QJEZeq7gs9kt+NLnXo9lfw2E18dAECcXpZZeJv7UZTjphjrzZCi95WqEfmUGWYBZgjderE6Ph9jXlB79dqPhqsmQZ3A7tNLAeK01JACJOXxTHJpB1U8f9rGXKHx/iCJgUdyJxh2RW0SaQWAO2Lwex8mb3X7I+Z7j2l6Lfu5Y8tanBx/bGRruPB+eMixa4lpNAUCgWqS+mu4yN8FV79a7zEAE4HeLVlsbm6mBAyquZHqfkY9kHxkFVTRIw5IQtBWlkDeAehcot1hH+AI5IYxsF4Mc2MLnFnhjjGS2Ib0w7znBOHNux8JZFrQMETGYOyJRs1 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/2/26 03:45, 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 > --- > 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); Ah, yes, code we will never trigger ;) Acked-by: David Hildenbrand (Arm) -- Cheers, David