The patch titled
Subject: mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==false
has been added to the -mm mm-unstable branch. Its filename is
mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Barry Song <v-songbaohua@xxxxxxxx>
Subject: mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==false
Date: Tue, 18 Jun 2024 11:11:36 +1200
For the !folio_test_anon(folio) case, we can now invoke
folio_add_new_anon_rmap() with the rmap flags set to either EXCLUSIVE or
non-EXCLUSIVE. This action will suppress the VM_WARN_ON_FOLIO check
within __folio_add_anon_rmap() while initiating the process of bringing up
mTHP swapin.
static __always_inline void __folio_add_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
unsigned long address, rmap_t flags, enum rmap_level level)
{
...
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(folio_test_large(folio) &&
level != RMAP_LEVEL_PMD, folio);
}
...
}
It also improves the code's readability. Currently, all new anonymous
folios calling folio_add_anon_rmap_ptes() are order-0. This ensures that
new folios cannot be partially exclusive; they are either entirely
exclusive or entirely shared.
Link: https://lkml.kernel.org/r/20240617231137.80726-3-21cnbao@xxxxxxxxx
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Tested-by: Shuai Yuan <yuanshuai@xxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 8 ++++++++
mm/swapfile.c | 13 +++++++++++--
2 files changed, 19 insertions(+), 2 deletions(-)
--- a/mm/memory.c~mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false
+++ a/mm/memory.c
@@ -4339,6 +4339,14 @@ check_folio:
if (unlikely(folio != swapcache && swapcache)) {
folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
folio_add_lru_vma(folio, vma);
+ } else if (!folio_test_anon(folio)) {
+ /*
+ * We currently only expect small !anon folios, for which we now
+ * that they are either fully exclusive or fully shared. If we
+ * ever get large folios here, we have to be careful.
+ */
+ VM_WARN_ON_ONCE(folio_test_large(folio));
+ folio_add_new_anon_rmap(folio, vma, address, rmap_flags);
} else {
folio_add_anon_rmap_ptes(folio, page, nr_pages, vma, address,
rmap_flags);
--- a/mm/swapfile.c~mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false
+++ a/mm/swapfile.c
@@ -1916,8 +1916,17 @@ static int unuse_pte(struct vm_area_stru
VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
if (pte_swp_exclusive(old_pte))
rmap_flags |= RMAP_EXCLUSIVE;
-
- folio_add_anon_rmap_pte(folio, page, vma, addr, rmap_flags);
+ /*
+ * We currently only expect small !anon folios, for which we now that
+ * they are either fully exclusive or fully shared. If we ever get
+ * large folios here, we have to be careful.
+ */
+ if (!folio_test_anon(folio)) {
+ VM_WARN_ON_ONCE(folio_test_large(folio));
+ folio_add_new_anon_rmap(folio, vma, addr, rmap_flags);
+ } else {
+ folio_add_anon_rmap_pte(folio, page, vma, addr, rmap_flags);
+ }
} else { /* ksm created a completely new copy */
folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
folio_add_lru_vma(folio, vma);
_
Patches currently in -mm which might be from v-songbaohua@xxxxxxxx are
cifs-drop-the-incorrect-assertion-in-cifs_swap_rw.patch
mm-remove-the-implementation-of-swap_free-and-always-use-swap_free_nr.patch
mm-introduce-pte_move_swp_offset-helper-which-can-move-offset-bidirectionally.patch
mm-introduce-arch_do_swap_page_nr-which-allows-restore-metadata-for-nr-pages.patch
mm-swap-reuse-exclusive-folio-directly-instead-of-wp-page-faults.patch
mm-introduce-pmdpte_needs_soft_dirty_wp-helpers-for-softdirty-write-protect.patch
mm-set-pte-writable-while-pte_soft_dirty-is-true-in-do_swap_page.patch
mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch
mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false.patch
mm-remove-folio_test_anonfolio==false-path-in-__folio_add_anon_rmap.patch
