+ tools-testing-selftests-mm-test-anonymous-page-offset-merge-behaviour.patch added to mm-unstable branch
Andrew Morton <[email protected]>
| Newsgroups | org.kernel.vger.mm-commits |
|---|---|
| Message-ID | <[email protected]> |
The patch titled
Subject: tools/testing/selftests/mm: test anonymous page offset merge behaviour
has been added to the -mm mm-unstable branch. Its filename is
tools-testing-selftests-mm-test-anonymous-page-offset-merge-behaviour.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-testing-selftests-mm-test-anonymous-page-offset-merge-behaviour.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <[email protected]>
Subject: tools/testing/selftests/mm: test anonymous page offset merge behaviour
Date: Thu, 13 Aug 2026 18:32:33 +0100
While maintaining anonymous page offsets for VMAs has no impact for most
merge cases, it does impact MAP_PRIVATE-mapped file-backed mappings which
happen to have matching page offset but not matching anonymous page
offset.
Assert this behaviour by attempting to map an unfaulted MAP_PRIVATE-memfd
region with a faulted one with compatible file page offsets but
incompatible anonymous page offsets.
Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-16-c21581c0c3c8@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Deucher <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Boris Brezillon <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Chengming Zhou <[email protected]>
Cc: Chris Li <[email protected]>
Cc: Christan König <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Claudio Imbrenda <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Gregory Price (Meta) <[email protected]>
Cc: Harry Yoo <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Huang Ray <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Janosch Frank <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kemeng Shi <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Liviu Dudau <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Marc Rutland <[email protected]>
Cc: "Masami Hiramatsu (Google)" <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Namhyung kim <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Pedro Falcato <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: Thomas Hellström <[email protected]>
Cc: Thomas Zimemrmann <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: xu xin <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
tools/testing/selftests/mm/merge.c | 57 +++++++++++++++++++++++++++
1 file changed, 57 insertions(+)
--- a/tools/testing/selftests/mm/merge.c~tools-testing-selftests-mm-test-anonymous-page-offset-merge-behaviour
+++ a/tools/testing/selftests/mm/merge.c
@@ -1305,6 +1305,63 @@ TEST_F(merge, merge_vmas_with_mseal)
ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 2 * page_size);
}
+TEST_F(merge, anon_and_page_offset_mismatch_memfd)
+{
+ struct procmap_fd *procmap = &self->procmap;
+ unsigned int page_size = self->page_size;
+ char *carveout = self->carveout;
+ char *ptr, *ptr2;
+ int fd;
+
+ /* Create a 10 page memfd descriptor. */
+ fd = memfd_create("anon_page_offset_test", MFD_CLOEXEC);
+ ASSERT_NE(fd, -1);
+ ASSERT_EQ(ftruncate(fd, 10 * page_size), 0);
+
+ /* Map a region using the memfd at page offset 0. */
+ ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE, fd, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /*
+ * Map another separately and trigger a CoW fault at page offset 5:
+ *
+ * |-----------| |---------|
+ * | unfaulted | | faulted |
+ * |-----------| |---------|
+ */
+ ptr2 = mmap(&carveout[10 * page_size], 5 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE,
+ fd, 5 * page_size);
+ ASSERT_NE(ptr2, MAP_FAILED);
+ ptr2[0] = 'x';
+
+ /*
+ * Now move it in place:
+ *
+ * |----------|
+ * | |
+ * v |
+ * |-----------| |---------|
+ * | unfaulted | | faulted |
+ * |-----------| |---------|
+ *
+ * Because the anonymous page offset of the faulted region is now
+ * &carveout[10 * page_size], despite the two regions being mergeable
+ * due to file page offset, they are NOT mergeable due to anonymous
+ * page offset.
+ */
+ ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+ MREMAP_MAYMOVE | MREMAP_FIXED,
+ &carveout[5 * page_size]);
+ ASSERT_NE(ptr2, MAP_FAILED);
+
+ /* Assert that they did not merge. */
+ ASSERT_TRUE(find_vma_procmap(procmap, ptr));
+ ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
+ ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size);
+}
+
TEST_F(merge_with_fork, mremap_faulted_to_unfaulted_prev)
{
struct procmap_fd *procmap = &self->procmap;
_
Patches currently in -mm which might be from [email protected] are
mm-vma-introduce-vma-anon-page-offset-field-and-add-helpers.patch
mm-provide-vma_is_cow_mapping-and-remove-is_cow_mapping.patch
mm-introduce-linear_anon_page_index.patch
mm-abstract-vma_address-and-introduce-vma_anon_address.patch
mm-update-print_bad_page_map-to-show-anon-index-if-appropriate.patch
mm-introduce-and-use-vma_filebacked_address.patch
mm-vma-fix-self-merge-check-in-copy_vma.patch
tools-testing-vma-add-tests-for-copy_vma-self-merge.patch
mm-propagate-vma-anonymous-page-offset-on-map-remap-split-merge.patch
mm-rmap-track-whether-the-page-vma-mapped-pgoff-is-anonymous.patch
mm-clean-up-vma_address_end.patch
mm-huge_memory-update-remove_migration_pmd-to-accept-a-folio.patch
mm-migrate-calculate-large-folio-page-index-using-pfn.patch
mm-rmap-use-anon-pgoff-to-track-map_private-file-backed-anon-folios.patch
tools-testing-vma-expand-vma-merge-tests-to-assert-anon-pgoff.patch
tools-testing-selftests-mm-test-anonymous-page-offset-merge-behaviour.patch
mm-add-some-missing-includes-to-mm-local-headers.patch
maintainers-add-drivers-char-memc-to-mm-misc-memory-mapping-sections.patch