linux-kernel - [PATCH 2/3] mm: rmap: remove lock_page

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Date:   Tue,  6 Dec 2022 18:13:40 +0100
From:   Johannes Weiner <hannes@...xchg.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] mm: rmap: remove lock_page_memcg()

The previous patch made sure charge moving only touches pages for
which page_mapped() is stable. lock_page_memcg() is no longer needed.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/rmap.c | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index b616870a09be..32e48b1c5847 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1222,9 +1222,6 @@ void page_add_anon_rmap(struct page *page,
 	bool compound = flags & RMAP_COMPOUND;
 	bool first = true;
 
-	if (unlikely(PageKsm(page)))
-		lock_page_memcg(page);
-
 	/* Is page being mapped by PTE? Is this its first map to be added? */
 	if (likely(!compound)) {
 		first = atomic_inc_and_test(&page->_mapcount);
@@ -1262,15 +1259,14 @@ void page_add_anon_rmap(struct page *page,
 	if (nr)
 		__mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
 
-	if (unlikely(PageKsm(page)))
-		unlock_page_memcg(page);
-
-	/* address might be in next vma when migration races vma_adjust */
-	else if (first)
-		__page_set_anon_rmap(page, vma, address,
-				     !!(flags & RMAP_EXCLUSIVE));
-	else
-		__page_check_anon_rmap(page, vma, address);
+	if (likely(!PageKsm(page))) {
+		/* address might be in next vma when migration races vma_adjust */
+		if (first)
+			__page_set_anon_rmap(page, vma, address,
+					     !!(flags & RMAP_EXCLUSIVE));
+		else
+			__page_check_anon_rmap(page, vma, address);
+	}
 
 	mlock_vma_page(page, vma, compound);
 }
@@ -1329,7 +1325,6 @@ void page_add_file_rmap(struct page *page,
 	bool first;
 
 	VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
-	lock_page_memcg(page);
 
 	/* Is page being mapped by PTE? Is this its first map to be added? */
 	if (likely(!compound)) {
@@ -1365,7 +1360,6 @@ void page_add_file_rmap(struct page *page,
 			NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped);
 	if (nr)
 		__mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
-	unlock_page_memcg(page);
 
 	mlock_vma_page(page, vma, compound);
 }
@@ -1394,8 +1388,6 @@ void page_remove_rmap(struct page *page,
 		return;
 	}
 
-	lock_page_memcg(page);
-
 	/* Is page being unmapped by PTE? Is this its last map to be removed? */
 	if (likely(!compound)) {
 		last = atomic_add_negative(-1, &page->_mapcount);
@@ -1451,8 +1443,6 @@ void page_remove_rmap(struct page *page,
 	 * and remember that it's only reliable while mapped.
 	 */
 
-	unlock_page_memcg(page);
-
 	munlock_vma_page(page, vma, compound);
 }
 
-- 
2.38.1