Re: [PATCH for-7.4 0/9] memcg: remove the v1 soft limit

[Shakeel Butt]

On Thu, Aug 13, 2026 at 10:27:09AM +0100, Lorenzo Stoakes (ARM) wrote:
> On Tue, Aug 11, 2026 at 01:31:54PM -0700, Shakeel Butt wrote:
> > Syzbot reported [1] a set_mm_walk() warning from kswapd. Soft limit
> > reclaim is the only thing that runs shrink_lruvec() from kswapd with a
> > target memcg set, and thus the only way kswapd can reach
> > lru_gen_shrink_lruvec() and in turn set_mm_walk(). The offender,
> > mem_cgroup_shrink_node(), has long carried a "Only used by soft limit
> > reclaim. Do not reuse for anything else." comment and a priority hack,
> > and it simply never got taught about MGLRU.
> >
> > Rather than teach it, let's delete it. The v1 soft limit was deprecated
> > in v6.12 by commit 569c4f62d84a ("memcg: initiate deprecation of v1
> > soft limit"). Nobody has reported depending on it in the ~21 months
> > since, and v2 has covered the same ground for a long time with
> > memory.low and memory.min.
> >
> > Link: https://lore.kernel.org/all/6a7a6929.b50370da.49fe0.005e.GAE@xxxxxxxxxx/ [1]
> >
> > Shakeel Butt (9):
> >   memcg: make the v1 soft limit knob inert
> >   memcg: remove v1 soft limit reclaim
> >   memcg: remove mem_cgroup_shrink_node()
> >   memcg: remove the soft limit reclaim tracepoints
> >   memcg: remove the soft limit rbtree
> >   memcg: remove lru_gen_soft_reclaim()
> >   memcg: remove the per-node soft limit tree fields
> >   memcg: remove mem_cgroup->soft_limit
> >   memcg: simplify v1 event ratelimiting
> >
> >  .../admin-guide/cgroup-v1/memory.rst          |  49 +-
> >  include/linux/memcontrol.h                    |  27 --
> >  include/linux/mmzone.h                        |  30 +-
> >  include/trace/events/vmscan.h                 |  14 -
> >  mm/internal.h                                 |   4 -
> >  mm/memcontrol-v1.c                            | 435 ++----------------
> >  mm/memcontrol-v1.h                            |  12 +-
> >  mm/memcontrol.c                               |   7 +-
> >  mm/vmscan.c                                   |  96 +---
> >  9 files changed, 66 insertions(+), 608 deletions(-)
> 
> This is a gorgeous diffstat :)
> 
> Obviously not my area but looking over it, all LGTM so feel free to add:
> 
> Acked-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> 
> To the whole series!

Thanks for the review.