The patch titled
Subject: doc: clarify refcount section by referring to folios & pages
has been added to the -mm mm-unstable branch. Its filename is
doc-clarify-refcount-section-by-referring-to-folios-pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/doc-clarify-refcount-section-by-referring-to-folios-pages.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: doc: clarify refcount section by referring to folios & pages
Date: Wed, 11 Jan 2023 14:28:49 +0000
Include the rename of subpages_mapcount to _nr_pages_mapped.
Link: https://lkml.kernel.org/r/20230111142915.1001531-4-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/mm/transhuge.rst | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
--- a/Documentation/mm/transhuge.rst~doc-clarify-refcount-section-by-referring-to-folios-pages
+++ a/Documentation/mm/transhuge.rst
@@ -112,20 +112,20 @@ Refcounts and transparent huge pages
Refcounting on THP is mostly consistent with refcounting on other compound
pages:
- - get_page()/put_page() and GUP operate on head page's ->_refcount.
+ - get_page()/put_page() and GUP operate on the folio->_refcount.
- ->_refcount in tail pages is always zero: get_page_unless_zero() never
succeeds on tail pages.
- - map/unmap of PMD entry for the whole compound page increment/decrement
- ->compound_mapcount, stored in the first tail page of the compound page;
- and also increment/decrement ->subpages_mapcount (also in the first tail)
- by COMPOUND_MAPPED when compound_mapcount goes from -1 to 0 or 0 to -1.
+ - map/unmap of a PMD entry for the whole THP increment/decrement
+ folio->_entire_mapcount and also increment/decrement
+ folio->_nr_pages_mapped by COMPOUND_MAPPED when _entire_mapcount
+ goes from -1 to 0 or 0 to -1.
- - map/unmap of sub-pages with PTE entry increment/decrement ->_mapcount
- on relevant sub-page of the compound page, and also increment/decrement
- ->subpages_mapcount, stored in first tail page of the compound page, when
- _mapcount goes from -1 to 0 or 0 to -1: counting sub-pages mapped by PTE.
+ - map/unmap of individual pages with PTE entry increment/decrement
+ page->_mapcount and also increment/decrement folio->_nr_pages_mapped
+ when page->_mapcount goes from -1 to 0 or 0 to -1 as this counts
+ the number of pages mapped by PTE.
split_huge_page internally has to distribute the refcounts in the head
page to the tail pages before clearing all PG_head/tail bits from the page
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
buffer-add-b_folio-as-an-alias-of-b_page.patch
buffer-replace-obvious-uses-of-b_page-with-b_folio.patch
buffer-use-b_folio-in-touch_buffer.patch
buffer-use-b_folio-in-end_buffer_async_read.patch
buffer-use-b_folio-in-end_buffer_async_write.patch
page_io-remove-buffer_head-include.patch
buffer-use-b_folio-in-mark_buffer_dirty.patch
gfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
jbd2-replace-obvious-uses-of-b_page-with-b_folio.patch
nilfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
reiserfs-replace-obvious-uses-of-b_page-with-b_folio.patch
mpage-use-b_folio-in-do_mpage_readpage.patch
mm-memcg-add-folio_memcg_check.patch
mm-remove-folio_pincount_ptr-and-head_compound_pincount.patch
mm-convert-head_subpages_mapcount-into-folio_nr_pages_mapped.patch
doc-clarify-refcount-section-by-referring-to-folios-pages.patch
mm-convert-total_compound_mapcount-to-folio_total_mapcount.patch
mm-convert-page_remove_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_anon_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_file_rmap-to-use-a-folio-internally.patch
mm-add-folio_add_new_anon_rmap.patch
page_alloc-use-folio-fields-directly.patch
mm-use-a-folio-in-hugepage_add_anon_rmap-and-hugepage_add_new_anon_rmap.patch
mm-use-entire_mapcount-in-__page_dup_rmap.patch
mm-debug-remove-call-to-head_compound_mapcount.patch
hugetlb-remove-uses-of-folio_mapcount_ptr.patch
mm-convert-page_mapcount-to-use-folio_entire_mapcount.patch
mm-remove-head_compound_mapcount-and-_ptr-functions.patch
mm-reimplement-compound_order.patch
mm-reimplement-compound_nr.patch
mm-convert-set_compound_page_dtor-and-set_compound_order-to-folios.patch
mm-convert-is_transparent_hugepage-to-use-a-folio.patch
mm-convert-destroy_large_folio-to-use-folio_dtor.patch
hugetlb-remove-uses-of-compound_dtor-and-compound_nr.patch
mm-remove-first-tail-page-members-from-struct-page.patch
doc-correct-struct-folio-kernel-doc.patch
mm-move-page-deferred_list-to-folio-_deferred_list.patch
mm-huge_memory-remove-page_deferred_list.patch
mm-huge_memory-convert-get_deferred_split_queue-to-take-a-folio.patch
mm-convert-deferred_split_huge_page-to-deferred_split_folio.patch
