linux-kernel - [PATCH v6 10/10] mm: revise the comments of mem_cgroup_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1576488386-32544-11-git-send-email-alex.shi@linux.alibaba.com>
Date:   Mon, 16 Dec 2019 17:26:26 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, tj@...nel.org, hughd@...gle.com,
        khlebnikov@...dex-team.ru, daniel.m.jordan@...cle.com,
        yang.shi@...ux.alibaba.com, willy@...radead.org,
        shakeelb@...gle.com, hannes@...xchg.org
Cc:     Alex Shi <alex.shi@...ux.alibaba.com>
Subject: [PATCH v6 10/10] mm: revise the comments of mem_cgroup_page_lruvec

From: Johannes Weiner <hannes@...xchg.org>

Better document the mem_cgroup_page_lruvec() caller requirements.

Suggested-by: Shakeel Butt <shakeelb@...gle.com>
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: cgroups@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
 mm/memcontrol.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f8e279487e1d..552de2e7da0e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1202,9 +1202,18 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
  * @page: the page
  * @pgdat: pgdat of the page
  *
- * This function is only safe when following the LRU page isolation
- * and putback protocol: the LRU lock must be held, and the page must
- * either be PageLRU() or the caller must have isolated/allocated it.
+ * NOTE: The returned lruvec is only stable if the calling context has
+ * the page->mem_cgroup pinned! This is accomplished by satisfying one
+ * of the following criteria:
+ *
+ *    a) have the @page locked
+ *    b) have an exclusive reference to @page (e.g. refcount 0)
+ *    c) hold the lru_lock and "own" the PageLRU (meaning either ensure
+ *       it's set, or be the one to hold the page in isolation)
+ *
+ * Otherwise, the page could be freed or moved out of the memcg,
+ * thereby releasing its reference on the memcg and potentially
+ * freeing it and its lruvecs in the process.
  */
 struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgdat)
 {
-- 
1.8.3.1