@@ -1353,6 +1353,33 @@ static void madvise_collapse_existing_thps(struct collapse_context *c,
ops->cleanup_area(p, hpage_pmd_size);
}
+/*
+ * Test race with khugepaged where page tables have been retracted and
+ * pmd cleared.
+ */
+static void madvise_retracted_page_tables(struct collapse_context *c,
+ struct mem_ops *ops)
+{
+ void *p;
+ int nr_hpages = 1;
+ unsigned long size = nr_hpages * hpage_pmd_size;
+
+ p = ops->setup_area(nr_hpages);
+ ops->fault(p, 0, size);
+
+ /* Let khugepaged collapse and leave pmd cleared */
+ if (wait_for_scan("Collapse and leave PMD cleared", p, nr_hpages,
+ ops)) {
+ fail("Timeout");
+ return;
+ }
+ success("OK");
+ c->collapse("Install huge PMD from page cache", p, nr_hpages, ops,
+ true);
+ validate_memory(p, 0, size);
+ ops->cleanup_area(p, size);
+}
+
static void usage(void)
{
fprintf(stderr, "\nUsage: ./khugepaged <test type> [dir]\n\n");
@@ -1524,5 +1551,8 @@ int main(int argc, const char **argv)
TEST(madvise_collapse_existing_thps, madvise_context, file_ops);
TEST(madvise_collapse_existing_thps, madvise_context, shmem_ops);
+ TEST(madvise_retracted_page_tables, madvise_context, file_ops);
+ TEST(madvise_retracted_page_tables, madvise_context, shmem_ops);
+
restore_settings(0);
}
This test tests that MADV_COLLAPSE acting on file/shmem memory for which (1) the file extent mapping by the memory is already a huge page in the page cache, and (2) the pmd mapping this memory in the target process is none. In practice, (1)+(2) is the state left over after khugepaged has successfully collapsed file/shmem memory for a target VMA, but the memory has not yet been refaulted. So, this test in-effect tests MADV_COLLAPSE racing with khugepaged to collapse the memory first. Link: https://lkml.kernel.org/r/20220907144521.3115321-10-zokeefe@google.com Signed-off-by: Zach O'Keefe <zokeefe@google.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Chris Kennelly <ckennelly@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Houghton <jthoughton@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com> Cc: SeongJae Park <sj@kernel.org> Cc: Song Liu <songliubraving@fb.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yang Shi <shy828301@gmail.com> --- tools/testing/selftests/vm/khugepaged.c | 30 +++++++++++++++++++++++++ 1 file changed, 30 insertions(+)