The patch titled
Subject: mm: always initialise folio->_deferred_list
has been added to the -mm mm-unstable branch. Its filename is
mm-always-initialise-folio-_deferred_list.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-always-initialise-folio-_deferred_list.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: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: always initialise folio->_deferred_list
Date: Thu, 21 Mar 2024 14:24:39 +0000
Patch series "Various significant MM patches".
These patches all interact in annoying ways which make it tricky to send
them out in any way other than a big batch, even though there's not really
an overarching theme to connect them.
The big effects of this patch series are:
- folio_test_hugetlb() becomes reliable, even when called without a
page reference
- We free up PG_slab, and we could always use more page flags
- We no longer need to check PageSlab before calling page_mapcount()
This patch (of 9):
For compound pages which are at least order-2 (and hence have a
deferred_list), initialise it and then we can check at free that the page
is not part of a deferred list. We recently found this useful to rule out
a source of corruption.
Link: https://lkml.kernel.org/r/20240321142448.1645400-1-willy@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240321142448.1645400-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 2 --
mm/hugetlb.c | 3 ++-
mm/internal.h | 2 ++
mm/memcontrol.c | 2 ++
mm/page_alloc.c | 9 +++++----
5 files changed, 11 insertions(+), 7 deletions(-)
--- a/mm/huge_memory.c~mm-always-initialise-folio-_deferred_list
+++ a/mm/huge_memory.c
@@ -771,8 +771,6 @@ void folio_prep_large_rmappable(struct f
{
if (!folio || !folio_test_large(folio))
return;
- if (folio_order(folio) > 1)
- INIT_LIST_HEAD(&folio->_deferred_list);
folio_set_large_rmappable(folio);
}
--- a/mm/hugetlb.c~mm-always-initialise-folio-_deferred_list
+++ a/mm/hugetlb.c
@@ -1796,7 +1796,8 @@ static void __update_and_free_hugetlb_fo
destroy_compound_gigantic_folio(folio, huge_page_order(h));
free_gigantic_folio(folio, huge_page_order(h));
} else {
- __free_pages(&folio->page, huge_page_order(h));
+ INIT_LIST_HEAD(&folio->_deferred_list);
+ folio_put(folio);
}
}
--- a/mm/internal.h~mm-always-initialise-folio-_deferred_list
+++ a/mm/internal.h
@@ -525,6 +525,8 @@ static inline void prep_compound_head(st
atomic_set(&folio->_entire_mapcount, -1);
atomic_set(&folio->_nr_pages_mapped, 0);
atomic_set(&folio->_pincount, 0);
+ if (order > 1)
+ INIT_LIST_HEAD(&folio->_deferred_list);
}
static inline void prep_compound_tail(struct page *head, int tail_idx)
--- a/mm/memcontrol.c~mm-always-initialise-folio-_deferred_list
+++ a/mm/memcontrol.c
@@ -7400,6 +7400,8 @@ static void uncharge_folio(struct folio
struct obj_cgroup *objcg;
VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
+ VM_BUG_ON_FOLIO(folio_order(folio) > 1 &&
+ !list_empty(&folio->_deferred_list), folio);
/*
* Nobody should be changing or seriously looking at
--- a/mm/page_alloc.c~mm-always-initialise-folio-_deferred_list
+++ a/mm/page_alloc.c
@@ -1007,10 +1007,11 @@ static int free_tail_page_prepare(struct
}
break;
case 2:
- /*
- * the second tail page: ->mapping is
- * deferred_list.next -- ignore value.
- */
+ /* the second tail page: deferred_list overlaps ->mapping */
+ if (unlikely(!list_empty(&folio->_deferred_list))) {
+ bad_page(page, "on deferred list");
+ goto out;
+ }
break;
default:
if (page->mapping != TAIL_MAPPING) {
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-increase-folio-batch-size.patch
mm-always-initialise-folio-_deferred_list.patch
mm-create-folio_flag_false-and-folio_type_ops-macros.patch
mm-remove-folio_prep_large_rmappable.patch
mm-support-page_mapcount-on-page_has_type-pages.patch
mm-turn-folio_test_hugetlb-into-a-pagetype.patch
mm-remove-a-call-to-compound_head-from-is_page_hwpoison.patch
mm-free-up-pg_slab.patch
mm-improve-dumping-of-mapcount-and-page_type.patch
hugetlb-remove-mention-of-destructors.patch
