+ mm-memcg-v1-fix-memsw-and-tcp-failcnt-accounting.patch added to mm-hotfixes-unstable branch

The patch titled
     Subject: mm: memcg-v1: fix memsw and TCP failcnt accounting
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-memcg-v1-fix-memsw-and-tcp-failcnt-accounting.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-v1-fix-memsw-and-tcp-failcnt-accounting.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Guopeng Zhang <[email protected]>
Subject: mm: memcg-v1: fix memsw and TCP failcnt accounting
Date: Tue, 11 Aug 2026 11:08:43 +0800

Commit 0e2759afcaf9 ("page_counter: track failcnt only for legacy
cgroups") made failcnt accounting conditional on track_failcnt.  It
enabled the flag for memcg->memory, but not for memcg->memsw or
memcg->tcpmem.

Consequently, memory.memsw.failcnt remains zero when the memory+swap limit
is hit.  memory.kmem.tcp.limit_in_bytes still sets memcg->tcpmem.max, but
TCP charge failures are not reflected in memory.kmem.tcp.failcnt.

Enable failcnt accounting for both v1 counters.

To reproduce memory.memsw.failcnt:

    CG=/sys/fs/cgroup/memory/memsw-test
    LIMIT=33554432
    mkdir "$CG"
    echo "$LIMIT" > "$CG/memory.limit_in_bytes"
    echo "$LIMIT" > "$CG/memory.memsw.limit_in_bytes"

Start a child process in the cgroup and make it allocate and touch 96 MiB
of memory, causing a memcg OOM.

    cat "$CG/memory.memsw.failcnt"

Without the patch, memory.memsw.failcnt is 0. With the patch,
memory.memsw.failcnt is greater than 0.

To reproduce memory.kmem.tcp.failcnt:

    CG=/sys/fs/cgroup/memory/tcpmem-test
    LIMIT=65536
    mkdir "$CG"
    echo "$LIMIT" > "$CG/memory.kmem.tcp.limit_in_bytes"

Start a child process in the cgroup, create a TCP socket, and reserve
1 MiB of socket memory with SO_RESERVE_MEM. The reservation fails with
ENOMEM.

    cat "$CG/memory.kmem.tcp.failcnt"

Without the patch, memory.kmem.tcp.failcnt is 0.  With the patch,
memory.kmem.tcp.failcnt is greater than 0.

Link: https://lore.kernel.org/[email protected]
Closes: https://sashiko.dev/#/patchset/[email protected]?part=1
Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")
Signed-off-by: Guopeng Zhang <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/memcontrol.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/memcontrol.c~mm-memcg-v1-fix-memsw-and-tcp-failcnt-accounting
+++ a/mm/memcontrol.c
@@ -4180,9 +4180,11 @@ mem_cgroup_css_alloc(struct cgroup_subsy
 		page_counter_init(&memcg->swap, &parent->swap, false);
 #ifdef CONFIG_MEMCG_V1
 		memcg->memory.track_failcnt = !memcg_on_dfl;
+		memcg->memsw.track_failcnt = !memcg_on_dfl;
 		WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
 		page_counter_init(&memcg->kmem, &parent->kmem, false);
 		page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);
+		memcg->tcpmem.track_failcnt = !memcg_on_dfl;
 #endif
 	} else {
 		init_memcg_stats();
_

Patches currently in -mm which might be from [email protected] are

mm-memcg-v1-fix-memsw-and-tcp-failcnt-accounting.patch
mm-memcg-v1-fix-memorymemswfailcnt-accounting.patch
mm-memcg-stop-reclaim-when-a-limit-update-is-superseded.patch