From 15b447361794271f4d03c04d82276a841fe06328 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Tue, 15 Dec 2020 14:21:31 -0800
Subject: mm/lru: revise the comments of lru_lock
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Since we changed the pgdat->lru_lock to lruvec->lru_lock, it's time to fix
the incorrect comments in code.  Also fixed some zone->lru_lock comment
error from ancient time.  etc.

I struggled to understand the comment above move_pages_to_lru() (surely
it never calls page_referenced()), and eventually realized that most of
it had got separated from shrink_active_list(): move that comment back.

Link: https://lkml.kernel.org/r/1604566549-62481-20-git-send-email-alex.shi@linux.alibaba.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Chen, Rong A" <rong.a.chen@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 Documentation/admin-guide/cgroup-v1/memory.rst | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

(limited to 'Documentation/admin-guide/cgroup-v1/memory.rst')

diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
index a44cd467d218..52688ae34461 100644
--- a/Documentation/admin-guide/cgroup-v1/memory.rst
+++ b/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -287,20 +287,17 @@ When oom event notifier is registered, event will be delivered.
 2.6 Locking
 -----------
 
-   lock_page_cgroup()/unlock_page_cgroup() should not be called under
-   the i_pages lock.
+Lock order is as follows:
 
-   Other lock order is following:
+  Page lock (PG_locked bit of page->flags)
+    mm->page_table_lock or split pte_lock
+      lock_page_memcg (memcg->move_lock)
+        mapping->i_pages lock
+          lruvec->lru_lock.
 
-   PG_locked.
-     mm->page_table_lock
-         pgdat->lru_lock
-	   lock_page_cgroup.
-
-  In many cases, just lock_page_cgroup() is called.
-
-  per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
-  pgdat->lru_lock, it has no lock of its own.
+Per-node-per-memcgroup LRU (cgroup's private LRU) is guarded by
+lruvec->lru_lock; PG_lru bit of page->flags is cleared before
+isolating a page from its LRU under lruvec->lru_lock.
 
 2.7 Kernel Memory Extension (CONFIG_MEMCG_KMEM)
 -----------------------------------------------
-- 
cgit v1.2.3