On Thu, Oct 24, 2024 at 11:16:52AM GMT, Michal Hocko wrote: > On Wed 23-10-24 23:57:12, Shakeel Butt wrote: > > The memcg v1's charge move feature has been deprecated. There is no need > > to have any locking or protection against the moving charge. Let's > > proceed to remove all the locking code related to charge moving. > > > > Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx> > > --- > > -/** > > - * folio_memcg_lock - Bind a folio to its memcg. > > - * @folio: The folio. > > - * > > - * This function prevents unlocked LRU folios from being moved to > > - * another cgroup. > > - * > > - * It ensures lifetime of the bound memcg. The caller is responsible > > - * for the lifetime of the folio. > > - */ > > -void folio_memcg_lock(struct folio *folio) > > -{ > > - struct mem_cgroup *memcg; > > - unsigned long flags; > > - > > - /* > > - * The RCU lock is held throughout the transaction. The fast > > - * path can get away without acquiring the memcg->move_lock > > - * because page moving starts with an RCU grace period. > > - */ > > - rcu_read_lock(); > > Is it safe to remove the implicit RCU? Good question. I think it will be safe to keep the RCU in this patch and in the followup examine each place and decide to remove RCU or not. Thanks for the review.