linux-kernel - [PATCH] mm: correctly charge compressed memory to its memcg

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Message-Id: <20221114194828.100822-1-hannes@cmpxchg.org>
Date:   Mon, 14 Nov 2022 14:48:28 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Li Liguang <liliguang@...du.com>,
        stable@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] mm: correctly charge compressed memory to its memcg

From: Li Liguang <liliguang@...du.com>

Kswapd will reclaim memory when memory pressure is high, the
annonymous memory will be compressed and stored in the zpool
if zswap is enabled. The memcg_kmem_bypass() in
get_obj_cgroup_from_page() will bypass the kernel thread and
cause the compressed memory not charged to its memory cgroup.

Remove the memcg_kmem_bypass() and properly charge compressed
memory to its corresponding memory cgroup.

Link: https://lore.kernel.org/linux-mm/CALvZod4nnn8BHYqAM4xtcR0Ddo2-Wr8uKm9h_CHWUaXw7g_DCg@mail.gmail.com/
Fixes: f4840ccfca25 ("zswap: memcg accounting")
Cc: stable@...r.kernel.org # 5.19+
Acked-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Shakeel Butt <shakeelb@...gle.com>
Reviewed-by: Muchun Song <songmuchun@...edance.com>
Signed-off-by: Li Liguang <liliguang@...du.com>
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

This fell through the cracks in summer as it didn't make it to the
right mailing lists. Resending.

I know it's close to 6.1-final, but the fix should be safe to put
in. It's straight-forward and obvious code-wise. We also have large
parts of production running on it without problems.

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2d8549ae1b30..a1a35c12635e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3026,7 +3026,7 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
 {
 	struct obj_cgroup *objcg;

-	if (!memcg_kmem_enabled() || memcg_kmem_bypass())
+	if (!memcg_kmem_enabled())
 		return NULL;

 	if (PageMemcgKmem(page)) {
-- 
2.38.1