On Wed, Jul 1, 2020 at 11:46 AM Roman Gushchin <guro@xxxxxx> wrote: ... > -- > > From c97afecd32c0db5e024be9ba72f43d22974f5bcd Mon Sep 17 00:00:00 2001 > From: Roman Gushchin <guro@xxxxxx> > Date: Wed, 1 Jul 2020 11:05:32 -0700 > Subject: [PATCH] mm: kmem: make memcg_kmem_enabled() irreversible > > Historically the kernel memory accounting was an opt-in feature, which > could be enabled for individual cgroups. But now it's not true, and > it's on by default both on cgroup v1 and cgroup v2. And as long as a > user has at least one non-root memory cgroup, the kernel memory > accounting is on. So in most setups it's either always on (if memory > cgroups are in use and kmem accounting is not disabled), either always > off (otherwise). > > memcg_kmem_enabled() is used in many places to guard the kernel memory > accounting code. If memcg_kmem_enabled() can reverse from returning > true to returning false (as now), we can't rely on it on release paths > and have to check if it was on before. > > If we'll make memcg_kmem_enabled() irreversible (always returning true > after returning it for the first time), it'll make the general logic > more simple and robust. It also will allow to guard some checks which > otherwise would stay unguarded. > > Signed-off-by: Roman Gushchin <guro@xxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
