On 13.9.2022 8.22, Alistair Popple wrote:
As noted by John Hubbard the original test relied on side effects of the
implementation of migrate_vma_setup() to detect if pages had been
swapped to disk or not. This is subject to change in future so
explicitly check for swap entries via pagemap instead. Fix a spelling
mistake while we're at it.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Fixes: 5cc88e844e87 ("selftests/hmm-tests: add test for dirty bits")
---
tools/testing/selftests/vm/hmm-tests.c | 50 +++++++++++++++++++++++---
1 file changed, 46 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
index 70fdb49b59ed..b5f6a7dc1f12 100644
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -1261,9 +1261,47 @@ static int destroy_cgroup(void)
return 0;
}
+static uint64_t get_pfn(int fd, uint64_t ptr)
+{
+ uint64_t pfn;
+ int ret;
+
+ ret = pread(fd, &pfn, sizeof(ptr),
+ (uint64_t) ptr / getpagesize() * sizeof(ptr));
+ if (ret != sizeof(ptr))
+ return 0;
+
+ return pfn;
+}
+
+#define PAGEMAP_SWAPPED (1ULL << 62)
+
+/* Returns true if at least one page in the range is on swap */
+static bool pages_swapped(void *ptr, unsigned long pages)
+{
+ uint64_t pfn;
+ int fd = open("/proc/self/pagemap", O_RDONLY);
+ unsigned long i;
+
+ if (fd < 0)
+ return false;
+
+ for (i = 0; i < pages; i++) {
+ pfn = get_pfn(fd, (uint64_t) ptr + i * getpagesize());
+
+ if (pfn & PAGEMAP_SWAPPED) {
+ close(fd);
+ return true;
+ }
+ }
+
+ close(fd);
+ return false;
+}
+
/*
* Try and migrate a dirty page that has previously been swapped to disk. This
- * checks that we don't loose dirty bits.
+ * checks that we don't lose dirty bits.
*/
TEST_F(hmm, migrate_dirty_page)
{
@@ -1300,6 +1338,10 @@ TEST_F(hmm, migrate_dirty_page)
ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30));
+ /* Make sure at least some pages got paged to disk. */
+ if (!pages_swapped(buffer->ptr, npages))
+ SKIP(return, "Pages weren't swapped when they should have been");
+
/* Fault pages back in from swap as clean pages */
for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
tmp += ptr[i];
@@ -1309,10 +1351,10 @@ TEST_F(hmm, migrate_dirty_page)
ptr[i] = i;
/*
- * Attempt to migrate memory to device, which should fail because
- * hopefully some pages are backed by swap storage.
+ * Attempt to migrate memory to device. This might fail if some pages
+ * are/were backed by swap but that's ok.
*/
- ASSERT_TRUE(hmm_migrate_sys_to_dev(self->fd, buffer, npages));
+ hmm_migrate_sys_to_dev(self->fd, buffer, npages);
ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30));
Reviewed-by: Mika Penttilä <mpenttil@xxxxxxxxxx>
