Patch "mm: memcg: add per-memcg zswap writeback stat" has been added to the 6.6-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    mm: memcg: add per-memcg zswap writeback stat

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-memcg-add-per-memcg-zswap-writeback-stat.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From leon.huangfu@shopee.com Mon Nov  3 08:53:08 2025
From: Leon Huang Fu <leon.huangfu@shopee.com>
Date: Mon,  3 Nov 2025 15:51:30 +0800
Subject: mm: memcg: add per-memcg zswap writeback stat
To: stable@vger.kernel.org, greg@kroah.com
Cc: tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, corbet@lwn.net, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, akpm@linux-foundation.org, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, lance.yang@linux.dev, leon.huangfu@shopee.com, shy828301@gmail.com, yosryahmed@google.com, sashal@kernel.org, vishal.moola@gmail.com, cerasuolodomenico@gmail.com, nphamcs@gmail.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Bagas Sanjaya <bagasdotme@gmail.com>, Chris Li <chrisl@kernel.org>, Shuah Khan <shuah@kernel.org>
Message-ID: <20251103075135.20254-3-leon.huangfu@shopee.com>

From: Domenico Cerasuolo <cerasuolodomenico@gmail.com>

[ Upstream commit 7108cc3f765cafd48a6a35f8add140beaecfa75b ]

Since zswap now writes back pages from memcg-specific LRUs, we now need a
new stat to show writebacks count for each memcg.

[nphamcs@gmail.com: rename ZSWP_WB to ZSWPWB]
  Link: https://lkml.kernel.org/r/20231205193307.2432803-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-5-nphamcs@gmail.com
Suggested-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Leon Huang Fu <leon.huangfu@shopee.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/vm_event_item.h |    1 +
 mm/memcontrol.c               |    1 +
 mm/vmstat.c                   |    1 +
 mm/zswap.c                    |    4 ++++
 4 files changed, 7 insertions(+)

--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -145,6 +145,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
 #ifdef CONFIG_ZSWAP
 		ZSWPIN,
 		ZSWPOUT,
+		ZSWPWB,
 #endif
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -700,6 +700,7 @@ static const unsigned int memcg_vm_event
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
 	ZSWPIN,
 	ZSWPOUT,
+	ZSWPWB,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	THP_FAULT_ALLOC,
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1397,6 +1397,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_ZSWAP
 	"zswpin",
 	"zswpout",
+	"zswpwb",
 #endif
 #ifdef CONFIG_X86
 	"direct_map_level2_splits",
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -674,6 +674,10 @@ static int zswap_reclaim_entry(struct zs
 		goto put_unlock;
 	}
 
+	if (entry->objcg)
+		count_objcg_event(entry->objcg, ZSWPWB);
+
+	count_vm_event(ZSWPWB);
 	/*
 	 * Writeback started successfully, the page now belongs to the
 	 * swapcache. Drop the entry from zswap - unless invalidate already


Patches currently in stable-queue which might be from leon.huangfu@shopee.com are

queue-6.6/mm-memcg-make-stats-flushing-threshold-per-memcg.patch
queue-6.6/mm-memcg-change-flush_next_time-to-flush_last_time.patch
queue-6.6/mm-memcg-restore-subtree-stats-flushing.patch
queue-6.6/mm-workingset-move-the-stats-flush-into-workingset_test_recent.patch
queue-6.6/mm-memcg-add-thp-swap-out-info-for-anonymous-reclaim.patch
queue-6.6/mm-memcg-add-per-memcg-zswap-writeback-stat.patch
queue-6.6/mm-memcg-move-vmstats-structs-definition-above-flushing-code.patch