selftests/mm: hmm-tests: add setup of HugeTLB pages

hmm-tests skips HugeTLB tests if there are no free huge pages prepared by
a wrapper script.

Add setup of HugeTLB pages to the test and make sure that the original
settings are restored on the test exit.

Since kselftest_harness runs fixture setup and the tests in child
processes, use HUGETLB_SETUP_DEFAULT_PAGES() that defines a constructor
that runs in the main process and add verification that there are enough
free huge pages to the tests that use them.

Replace exit() calls with _exit() to avoid restoring HugeTLB settings in
the middle of test and use SIGKILL to kill a child process in
hmm_cow_in_device test to avoid interference with signal handlers in
hugepage_restore_settings().

Link: https://lore.kernel.org/20260511162840.375890-36-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: Luiz Capitulino <luizcap@redhat.com>
Tested-by: Sarthak Sharma <sarthak.sharma@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Li Wang <li.wang@linux.dev>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 12 insertions, 10 deletions

diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 43341154f07c..46e0c8c921c3 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -69,6 +69,9 @@ enum {
 #ifndef FOLL_LONGTERM
 #define FOLL_LONGTERM   0x100 /* mapping lifetime is indefinite */
 #endif
+
+HUGETLB_SETUP_DEFAULT_PAGES(1)
+
 FIXTURE(hmm)
 {
 	int		fd;
@@ -632,7 +635,7 @@ TEST_F(hmm, anon_write_child)
 			}
 
 			close(child_fd);
-			exit(0);
+			_exit(0);
 		}
 	}
 }
@@ -712,7 +715,7 @@ TEST_F(hmm, anon_write_child_shared)
 		ASSERT_EQ(ptr[i], -i);
 
 	close(child_fd);
-	exit(0);
+	_exit(0);
 }
 
 /*
@@ -784,8 +787,8 @@ TEST_F(hmm, anon_write_hugetlbfs)
 	int *ptr;
 	int ret;
 
-	if (!default_hsize)
-		SKIP(return, "Huge page size could not be determined");
+	if (!hugetlb_free_default_pages())
+		SKIP(return, "Not enough huge pages");
 
 	size = ALIGN(TWOMEG, default_hsize);
 	npages = size >> self->page_shift;
@@ -1614,9 +1617,8 @@ TEST_F(hmm, compound)
 	unsigned long i;
 
 	/* Skip test if we can't allocate a hugetlbfs page. */
-
-	if (!default_hsize)
-		SKIP(return, "Huge page size could not be determined");
+	if (!hugetlb_free_default_pages())
+		SKIP(return, "Not enough huge pages");
 
 	size = ALIGN(TWOMEG, default_hsize);
 	npages = size >> self->page_shift;
@@ -2062,7 +2064,7 @@ TEST_F(hmm, hmm_cow_in_device)
 	if (pid == -1)
 		ASSERT_EQ(pid, 0);
 	if (!pid) {
-		/* Child process waits for SIGTERM from the parent. */
+		/* Child process waits for SIGKILL from the parent. */
 		while (1) {
 		}
 		/* Should not reach this */
@@ -2075,10 +2077,10 @@ TEST_F(hmm, hmm_cow_in_device)
 		ptr[i] = i;
 
 	/* Terminate child and wait */
-	EXPECT_EQ(0, kill(pid, SIGTERM));
+	EXPECT_EQ(0, kill(pid, SIGKILL));
 	EXPECT_EQ(pid, waitpid(pid, &status, 0));
 	EXPECT_NE(0, WIFSIGNALED(status));
-	EXPECT_EQ(SIGTERM, WTERMSIG(status));
+	EXPECT_EQ(SIGKILL, WTERMSIG(status));
 
 	/* Take snapshot to CPU pagetables */
 	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);