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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230306154138.3775-3-findns94@gmail.com> X-Rspam-User: X-Rspamd-Queue-Id: BAC2F4000D X-Rspamd-Server: rspam01 X-Stat-Signature: 9sn4heihi1j8gzyi1jxnwyctrdkug9nj X-HE-Tag: 1678125017-604572 X-HE-Meta: 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 Uv8GwWGq 9WDk+E6pm0wJXvc14M+k/Mv7xNWLYtTDv3ByrGwwHkbYk9o2SAG4oRe6XsNJTBp+Zf9XyfOmyqlFSkibgqJjK6xlC8ksj0PIIl6W6kIwO9IMzw7pL5SR0aD/OEmr1ydRB3+PsmdkpoPSMPUw9qvI1ifc9SGt0l4QQ8xOxHOvkv963oOgpNsM9AzvgNrjKY1QpWgf5lAYWDdCWwQ9FWMiYNGDPlXmUAwNHvcbpA9aIDMur8YxRpLAC+MD10A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 06-03-23 23:41:36, Yue Zhao wrote: > The knob for cgroup v1 memory controller: memory.swappiness > is not protected by any locking so it can be modified while it is used. > This is not an actual problem because races are unlikely. > But it is better to use READ_ONCE/WRITE_ONCE to prevent compiler from > doing anything funky. > > The access of memcg->swappiness and vm_swappiness is lockless, > so both of them can be concurrently set at the same time > as we are trying to read them. > > Signed-off-by: Yue Zhao Acked-by: Michal Hocko Thanks! > --- > include/linux/swap.h | 8 ++++---- > mm/memcontrol.c | 4 ++-- > 2 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 209a425739a9..3f3fe43d1766 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -620,18 +620,18 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) > { > /* Cgroup2 doesn't have per-cgroup swappiness */ > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > - return vm_swappiness; > + return READ_ONCE(vm_swappiness); > > /* root ? */ > if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > - return vm_swappiness; > + return READ_ONCE(vm_swappiness); > > - return memcg->swappiness; > + return READ_ONCE(memcg->swappiness); > } > #else > static inline int mem_cgroup_swappiness(struct mem_cgroup *mem) > { > - return vm_swappiness; > + return READ_ONCE(vm_swappiness); > } > #endif > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 06821e5f7604..dca895c66a9b 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4179,9 +4179,9 @@ static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css, > return -EINVAL; > > if (!mem_cgroup_is_root(memcg)) > - memcg->swappiness = val; > + WRITE_ONCE(memcg->swappiness, val); > else > - vm_swappiness = val; > + WRITE_ONCE(vm_swappiness, val); > > return 0; > } > -- > 2.17.1 -- Michal Hocko SUSE Labs