Commit 02916a9c authored by David Hildenbrand's avatar David Hildenbrand Committed by Liu Shixin
Browse files

mm/rmap: add fast-path for small folios when adding/removing/duplicating 

mainline inclusion
from mainline-v6.10-rc1
commit 46d62de7ad1286854e0c2944ad26a1c1b1a5f191
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAE0PK

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=46d62de7ad1286854e0c2944ad26a1c1b1a5f191

--------------------------------

Let's add a fast-path for small folios to all relevant rmap functions.
Note that only RMAP_LEVEL_PTE applies.

This is a preparation for tracking the mapcount of large folios in a
single value.

Link: https://lkml.kernel.org/r/20240409192301.907377-4-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarYin Fengwei <fengwei.yin@intel.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 2a4c6719

include/linux/rmap.h

+13 −0
Original line number Diff line number Diff line
@@ -319,6 +319,11 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio, 


	switch (level) {

	case RMAP_LEVEL_PTE:

		if (!folio_test_large(folio)) {

			atomic_inc(&page->_mapcount);

			break;

		}



		do {

			atomic_inc(&page->_mapcount);

		} while (page++, --nr_pages > 0);
@@ -402,6 +407,14 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio, 
				if (PageAnonExclusive(page + i))

					return -EBUSY;

		}



		if (!folio_test_large(folio)) {

			if (PageAnonExclusive(page))

				ClearPageAnonExclusive(page);

			atomic_inc(&page->_mapcount);

			break;

		}



		do {

			if (PageAnonExclusive(page))

				ClearPageAnonExclusive(page);

mm/rmap.c

+16 −10
Original line number Diff line number Diff line
@@ -1137,15 +1137,18 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio, 


	switch (level) {

	case RMAP_LEVEL_PTE:

		if (!folio_test_large(folio)) {

			nr = atomic_inc_and_test(&page->_mapcount);

			break;

		}



		do {

			first = atomic_inc_and_test(&page->_mapcount);

			if (first && folio_test_large(folio)) {

			if (first) {

				first = atomic_inc_return_relaxed(mapped);

				first = (first < ENTIRELY_MAPPED);

			}



			if (first)

				if (first < ENTIRELY_MAPPED)

					nr++;

			}

		} while (page++, --nr_pages > 0);

		break;

	case RMAP_LEVEL_PMD:
@@ -1480,15 +1483,18 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, 


	switch (level) {

	case RMAP_LEVEL_PTE:

		if (!folio_test_large(folio)) {

			nr = atomic_add_negative(-1, &page->_mapcount);

			break;

		}



		do {

			last = atomic_add_negative(-1, &page->_mapcount);

			if (last && folio_test_large(folio)) {

			if (last) {

				last = atomic_dec_return_relaxed(mapped);

				last = (last < ENTIRELY_MAPPED);

			}



			if (last)

				if (last < ENTIRELY_MAPPED)

					nr++;

			}

		} while (page++, --nr_pages > 0);



		partially_mapped = nr && atomic_read(mapped);