selftests: hugetlb_dio: check for initial conditions to skip in the start

The test should be skipped if initial conditions aren't fulfilled in the
start instead of failing and outputting non-compliant TAP logs.  This kind
of failure pollutes the results.  The initial conditions are:

- The test should only execute if /tmp file can be allocated.
- The test should only execute if huge pages are free.

Before:
TAP version 13
1..4
Bail out! Error opening file
: Read-only file system (30)
 # Planned tests != run tests (4 != 0)
 # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0

After:
TAP version 13
1..0 # SKIP Unable to allocate file: Read-only file system

Link: https://lkml.kernel.org/r/20241101141557.3159432-1-usama.anjum@collabora.com
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Fixes: 3a103b5315b7 ("selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()")
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/hugetlb_dio.c b/tools/testing/selftests/mm/hugetlb_dio.c
index f9ac20c657ec6e3c71c5bd9e3142a52cf1a558fc..60001c142ce9984607a8d5c23ae4a823d0b10891 100644 (file)
--- a/tools/testing/selftests/mm/hugetlb_dio.c
+++ b/tools/testing/selftests/mm/hugetlb_dio.c
@@ -44,13 +44,6 @@ void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
        if (fd < 0)
                ksft_exit_fail_perror("Error opening file\n");
 
-       /* Get the free huge pages before allocation */
-       free_hpage_b = get_free_hugepages();
-       if (free_hpage_b == 0) {
-               close(fd);
-               ksft_exit_skip("No free hugepage, exiting!\n");
-       }
-
        /* Allocate a hugetlb page */
        orig_buffer = mmap(NULL, h_pagesize, mmap_prot, mmap_flags, -1, 0);
        if (orig_buffer == MAP_FAILED) {
@@ -94,8 +87,20 @@ void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
 int main(void)
 {
        size_t pagesize = 0;
+       int fd;
 
        ksft_print_header();
+
+       /* Open the file to DIO */
+       fd = open("/tmp", O_TMPFILE | O_RDWR | O_DIRECT, 0664);
+       if (fd < 0)
+               ksft_exit_skip("Unable to allocate file: %s\n", strerror(errno));
+       close(fd);
+
+       /* Check if huge pages are free */
+       if (!get_free_hugepages())
+               ksft_exit_skip("No free hugepage, exiting\n");
+
        ksft_set_plan(4);
 
        /* Get base page size */