selftests/mm: compaction_test: fix incorrect write of zero to nr_hugepages

[ Upstream commit 9ad665ef55eaad1ead1406a58a34f615a7c18b5e ]

Currently, the test tries to set nr_hugepages to zero, but that is not
actually done because the file offset is not reset after read().  Fix that
using lseek().

Link: https://lkml.kernel.org/r/20240521074358.675031-3-dev.jain@arm.com
Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
Signed-off-by: Dev Jain <dev.jain@arm.com>
Cc: <stable@vger.kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Sri Jayaramappa <sjayaram@akamai.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/testing/selftests/vm/compaction_test.c b/tools/testing/selftests/vm/compaction_test.c
index bcec71250873108efdeae50eab0874b3924204c4..cb2db2102dd2693ff7a63de4fe627c40f99bd515 100644 (file)
--- a/tools/testing/selftests/vm/compaction_test.c
+++ b/tools/testing/selftests/vm/compaction_test.c
@@ -102,6 +102,8 @@ int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
                goto close_fd;
        }
 
+       lseek(fd, 0, SEEK_SET);
+
        /* Start with the initial condition of 0 huge pages*/
        if (write(fd, "0", sizeof(char)) != sizeof(char)) {
                perror("Failed to write 0 to /proc/sys/vm/nr_hugepages\n");