selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages

Let's test whether R/O long-term pinning is reliable for non-anonymous
memory: when R/O long-term pinning a page, the expectation is that we
break COW early before pinning, such that actual write access via the
page tables won't break COW later and end up replacing the R/O-pinned
page in the page table.

Consequently, R/O long-term pinning in private mappings would only target
exclusive anonymous pages.

For now, all tests fail:
	# [RUN] R/O longterm GUP pin ... with shared zeropage
	not ok 151 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd
	not ok 152 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with tmpfile
	not ok 153 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with huge zeropage
	not ok 154 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd hugetlb (2048 kB)
	not ok 155 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd hugetlb (1048576 kB)
	not ok 156 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with shared zeropage
	not ok 157 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd
	not ok 158 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with tmpfile
	not ok 159 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with huge zeropage
	not ok 160 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (2048 kB)
	not ok 161 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (1048576 kB)
	not ok 162 Longterm R/O pin is reliable

Link: https://lkml.kernel.org/r/20221116102659.70287-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/cow.c b/tools/testing/selftests/vm/cow.c
index fb07bd44529c3d29d2102cca4dd006b6b8dd07bc..73e05b52c49ed100ef2fa982e39263088f188bce 100644 (file)
--- a/tools/testing/selftests/vm/cow.c
+++ b/tools/testing/selftests/vm/cow.c
@@ -561,6 +561,7 @@ static void test_iouring_fork(char *mem, size_t size)
 #endif /* LOCAL_CONFIG_HAVE_LIBURING */
 
 enum ro_pin_test {
+       RO_PIN_TEST,
        RO_PIN_TEST_SHARED,
        RO_PIN_TEST_PREVIOUSLY_SHARED,
        RO_PIN_TEST_RO_EXCLUSIVE,
@@ -593,6 +594,8 @@ static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test,
        }
 
        switch (test) {
+       case RO_PIN_TEST:
+               break;
        case RO_PIN_TEST_SHARED:
        case RO_PIN_TEST_PREVIOUSLY_SHARED:
                /*
@@ -1193,6 +1196,16 @@ static void test_cow(char *mem, const char *smem, size_t size)
        free(old);
 }
 
+static void test_ro_pin(char *mem, const char *smem, size_t size)
+{
+       do_test_ro_pin(mem, size, RO_PIN_TEST, false);
+}
+
+static void test_ro_fast_pin(char *mem, const char *smem, size_t size)
+{
+       do_test_ro_pin(mem, size, RO_PIN_TEST, true);
+}
+
 static void run_with_zeropage(non_anon_test_fn fn, const char *desc)
 {
        char *mem, *smem, tmp;
@@ -1433,7 +1446,7 @@ struct non_anon_test_case {
 };
 
 /*
- * Test cases that target any pages in private mappings that are non anonymous:
+ * Test cases that target any pages in private mappings that are not anonymous:
  * pages that may get shared via COW ndependent of fork(). This includes
  * the shared zeropage(s), pagecache pages, ...
  */
@@ -1446,6 +1459,19 @@ static const struct non_anon_test_case non_anon_test_cases[] = {
                "Basic COW",
                test_cow,
        },
+       /*
+        * Take a R/O longterm pin. When modifying the page via the page table,
+        * the page content change must be visible via the pin.
+        */
+       {
+               "R/O longterm GUP pin",
+               test_ro_pin,
+       },
+       /* Same as above, but using GUP-fast. */
+       {
+               "R/O longterm GUP-fast pin",
+               test_ro_fast_pin,
+       },
 };
 
 static void run_non_anon_test_case(struct non_anon_test_case const *test_case)