From 6d544529f97167162486e93bea035e08daa4d053 Mon Sep 17 00:00:00 2001 From: Vineet Agarwal Date: Tue, 12 May 2026 13:19:24 +0530 Subject: [PATCH] selftests/mm: check file initialization writes in split_huge_page_test 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. [akpm@linux-foundation.org: remove unneeded local, per David] Link: https://lore.kernel.org/da82de92-29d8-457c-9f65-40fc4900b922@kernel.org Link: https://lore.kernel.org/20260512074924.27721-1-agarwal.vineet2006@gmail.com Signed-off-by: Vineet Agarwal Acked-by: David Hildenbrand (Arm) Cc: Lorenzo Stoakes Cc: Wei Yang Cc: Vineet Agarwal Cc: Lorenzo Stoakes Signed-off-by: Andrew Morton --- tools/testing/selftests/mm/split_huge_page_test.c | 10 +++++++--- 1 file changed, 7 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..a8725942ee51 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -609,9 +609,13 @@ 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)) { + if (write(*fd, buf, sizeof(buf)) != sizeof(buf)) { + ksft_perror("write testfile"); + close(*fd); + goto err_out_unlink; + } + } close(*fd); sync(); *fd = open("/proc/sys/vm/drop_caches", O_WRONLY);