selftests/vm: add selftest to verify recollapse of THPs

Add selftest specific to madvise collapse context that tests MADV_COLLAPSE
is "successful" if a hugepage-aligned/sized region is already pmd-mapped.

This test also verifies that MADV_COLLAPSE can collapse memory into THPs
even in "madvise" THP mode and the memory isn't marked VM_HUGEPAGE.

Link: https://lkml.kernel.org/r/20220706235936.2197195-18-zokeefe@google.com
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.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: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/khugepaged.c b/tools/testing/selftests/vm/khugepaged.c
index 780f044..87cd0b9 100644 (file)
--- a/tools/testing/selftests/vm/khugepaged.c
+++ b/tools/testing/selftests/vm/khugepaged.c
@@ -990,6 +990,36 @@ static void collapse_max_ptes_shared(struct collapse_context *c)
        munmap(p, hpage_pmd_size);
 }
 
+static void madvise_collapse_existing_thps(void)
+{
+       void *p;
+       int err;
+
+       p = alloc_mapping();
+       fill_memory(p, 0, hpage_pmd_size);
+
+       printf("Collapse fully populated PTE table...");
+       /*
+        * Note that we don't set MADV_HUGEPAGE here, which
+        * also tests that VM_HUGEPAGE isn't required for
+        * MADV_COLLAPSE in "madvise" mode.
+        */
+       err = madvise(p, hpage_pmd_size, MADV_COLLAPSE);
+       if (err == 0 && check_huge(p)) {
+               success("OK");
+               printf("Re-collapse PMD-mapped hugepage");
+               err = madvise(p, hpage_pmd_size, MADV_COLLAPSE);
+               if (err == 0 && check_huge(p))
+                       success("OK");
+               else
+                       fail("Fail");
+       } else {
+               fail("Fail");
+       }
+       validate_memory(p, 0, hpage_pmd_size);
+       munmap(p, hpage_pmd_size);
+}
+
 int main(int argc, const char **argv)
 {
        struct collapse_context c;
@@ -1057,6 +1087,7 @@ int main(int argc, const char **argv)
                collapse_fork(&c);
                collapse_fork_compound(&c);
                collapse_max_ptes_shared(&c);
+               madvise_collapse_existing_thps();
        }
 
        restore_settings(0);