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Fri, 15 May 2026 02:22:13 -0700 (PDT) Date: Fri, 15 May 2026 09:22:11 +0000 From: Wei Yang To: Vineet Agarwal Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests/mm: check file initialization writes in split_huge_page_test Message-ID: <20260515092211.qkmaxcofxwfdexld@master> Reply-To: Wei Yang References: <20260512074924.27721-1-agarwal.vineet2006@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512074924.27721-1-agarwal.vineet2006@gmail.com> User-Agent: NeoMutt/20170113 (1.7.2) On Tue, May 12, 2026 at 01:19:24PM +0530, Vineet Agarwal wrote: >create_pagecache_thp_and_fd() fills the backing file for the >pagecache THP tests using repeated write() calls, but the return >value is never checked. > >If a write fails or completes only partially, the test may continue >with an incompletely initialized file and produce misleading results. > >Check the result of write() and fail the test if the expected number >of bytes was not written. > >Signed-off-by: Vineet Agarwal >--- > tools/testing/selftests/mm/split_huge_page_test.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > >diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c >index 500d07c4938b..eab69b0f59a0 100644 >--- a/tools/testing/selftests/mm/split_huge_page_test.c >+++ b/tools/testing/selftests/mm/split_huge_page_test.c >@@ -609,9 +609,16 @@ static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, > assert(fd_size % sizeof(buf) == 0); > for (i = 0; i < sizeof(buf); i++) > buf[i] = (unsigned char)i; >- for (i = 0; i < fd_size; i += sizeof(buf)) >- write(*fd, buf, sizeof(buf)); >- >+ for (i = 0; i < fd_size; i += sizeof(buf)) { >+ ssize_t written; >+ >+ written = write(*fd, buf, sizeof(buf)); >+ if (written != sizeof(buf)) { >+ ksft_perror("write testfile"); >+ close(*fd); >+ goto err_out_unlink; Maybe we can "goto err_out_close" and remove the close() here? Apart from this, I found on error writing to /proc/sys/vm/drop_caches in below, it just goto err_out_unlink, which left fd open. How about fix that at the same time. Generally, the change look good. >+ } >+ } > close(*fd); > sync(); > *fd = open("/proc/sys/vm/drop_caches", O_WRONLY); >-- >2.54.0 > -- Wei Yang Help you, Help me