On Mon, 2 May 2022 18:49:42 -0400 Joel Savitz jsavitz@redhat.com wrote:
The gup_test binary will fail showing only the output of perror("open") in the case that /sys/kernel/debug/gup_test is not found. This will almost always be due to CONFIG_GUP_TEST not being set, which enables compilation of a kernel that provides this file.
Add a short error message to clarify this failure and point the user to the solution.
--- a/tools/testing/selftests/vm/gup_test.c +++ b/tools/testing/selftests/vm/gup_test.c @@ -18,6 +18,8 @@ #define FOLL_WRITE 0x01 /* check pte is writable */ #define FOLL_TOUCH 0x02 /* mark page accessed */ +#define GUP_TEST_FILE "/sys/kernel/debug/gup_test"
static unsigned long cmd = GUP_FAST_BENCHMARK; static int gup_fd, repeats = 1; static unsigned long size = 128 * MB; @@ -204,9 +206,11 @@ int main(int argc, char **argv) if (write) gup.gup_flags |= FOLL_WRITE;
- gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
- gup_fd = open(GUP_TEST_FILE, O_RDWR); if (gup_fd == -1) { perror("open");
fprintf(stderr, "Unable to open %s: check that CONFIG_GUP_TEST=y\n",GUP_TEST_FILE);
Sidhartha did a similar thing: https://lkml.kernel.org/r/20220405214809.3351223-1-sidhartha.kumar@oracle.co...
(Which is now in mm-stable at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm)
Although in retroreview, it should have printed that to stderr rather than to stdout.