The quilt patch titled
Subject: doc: clarify refcount section by referring to folios & pages
has been removed from the -mm tree. Its filename was
doc-clarify-refcount-section-by-referring-to-folios-pages.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
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>
---
--- 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
