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mm: always initialise folio->_deferred_list 

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.

[peterx@redhat.com: always initialise folio->_deferred_list]
  Link: https://lkml.kernel.org/r/20240417211836.2742593-2-peterx@redhat.com
Link: https://lkml.kernel.org/r/20240321142448.1645400-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240321142448.1645400-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-03-21 14:24:39 +00:00 committed by Andrew Morton
parent 3b89ec4174
commit b7b098cf00
5 changed files with 12 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
mm/huge_memory.c
View File

@ -793,8 +793,6 @@ void folio_prep_large_rmappable(struct folio *folio)
{
if (!folio || !folio_test_large(folio))
return;
if (folio_order(folio) > 1)
INIT_LIST_HEAD(&folio->_deferred_list);
folio_set_large_rmappable(folio);
}

3
mm/hugetlb.c
View File

@ -1796,7 +1796,8 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
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);
}
}

2
mm/internal.h
View File

@ -525,6 +525,8 @@ static inline void prep_compound_head(struct page *page, unsigned int order)
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)

3
mm/memcontrol.c
View File

@ -7400,6 +7400,9 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
struct obj_cgroup *objcg;
VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
VM_BUG_ON_FOLIO(folio_order(folio) > 1 &&
!folio_test_hugetlb(folio) &&
!list_empty(&folio->_deferred_list), folio);
/*
* Nobody should be changing or seriously looking at

9
mm/page_alloc.c
View File

@ -1007,10 +1007,11 @@ static int free_tail_page_prepare(struct page *head_page, struct page *page)
}
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) {