On Wed, May 25, 2022 at 08:37:58AM -0400, Johannes Weiner wrote: > On Wed, May 25, 2022 at 03:57:17PM +0800, Muchun Song wrote: > > On Tue, May 24, 2022 at 07:36:24PM -0700, Roman Gushchin wrote: > > > On Tue, May 24, 2022 at 02:05:41PM +0800, Muchun Song wrote: > > > > - memcg_reparent_list_lrus(memcg, parent); > > > > + memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg)); > > > We effectively dropped this: > > > if (!parent) > > > parent = root_mem_cgroup; > > > Is it safe? (assuming v1 non-hierarchical mode, it's usually when all > > > is getting complicated) > > Yes, it's correct. But it's a quiet, incidental cleanup, so I can see > why it's confusing. It might be better to split the dead code removal > into a separate patch - with the following in the changelog ;): > Well, I can split the dead code removal into a separate patch. :-) Thanks. > > Since no-hierarchy mode is deprecated after commit bef8620cd8e0 > > ("mm: memcg: deprecate the non-hierarchical mode"), so > > parent_mem_cgroup() cannot return a NULL except root memcg, > > however, root memcg will not be offline, so it is safe. Right? >