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Sun, 29 Mar 2026 05:27:31 -0400 X-MC-Unique: iXW6Oc3oMs2_m6qiq-31ZA-1 X-Mimecast-MFC-AGG-ID: iXW6Oc3oMs2_m6qiq-31ZA_1774776449 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6C4281800344; Sun, 29 Mar 2026 09:27:28 +0000 (UTC) Received: from gmail.com (unknown [10.72.112.11]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6265319560B1; Sun, 29 Mar 2026 09:27:17 +0000 (UTC) Date: Sun, 29 Mar 2026 17:27:13 +0800 From: Chunyu Hu To: Mike Rapoport 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 In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-MFC-PROC-ID: aXgo_Jx8WjZ9iIS_-Vqnfmaftxp-pBFbT350Kb3rHwg_1774776449 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Stat-Signature: 54twb39qekrpboocos5u61rizaj9hb8r X-Rspamd-Queue-Id: 4FC4720007 X-Rspamd-Server: rspam09 X-HE-Tag: 1774776457-122104 X-HE-Meta: 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 3nQU4qAc BFWzlhnP4e9vdK6HXM92tMxpjplxN0k3uVIilPrM8kT5yisJlt+uPSM+OsboXdUB04e9aCdr2dl+l+Up+T7a1hLwPfVe30/sHA7M4IQefiPCrGSD99RyQvsZL3dF5BbNMw84+/3y4oD0mLDSzumnHaGlzhnpqRjhvM/K4Z7isx+EpzqwFryfrWxCz0iTXeFRAJBw2T6pmvE2uip4BsxT5Bhpck8Z3+eY6MykGzcZ43GKfVsBrkVHebBQLZDNe0w2+SqCcKjJQXwkBrZ1FyjYFZSbcbAxopMwSUCDH3rDOSuKTHQJamSVmhapF1TtsOzulHem/rGgPFis5ZLn5RX0sGdTRvpuP5K1jbmG6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 27, 2026 at 03:32:01PM +0300, Mike Rapoport wrote: > 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 the ksft_exit_fail_perror() don't accept the fmt string, it only accept a single string as parameter. ``` static inline __noreturn void ksft_exit_fail_perror(const char *msg) ``` But we can change it also support va_list arg like ksft_exit_fail_msg(msg, ...) does: static inline __noreturn void ksft_exit_fail_perror(msg, ...) I can have a try in next version. > > > > > 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. Same answer with above coment. > > > + 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. >