On Wed, Nov 29, 2023 at 03:21:52AM +0000, Yosry Ahmed wrote: > The workingset code flushes the stats in workingset_refault() to get > accurate stats of the eviction memcg. In preparation for more scoped > flushed and passing the eviction memcg to the flush call, move the call > to workingset_test_recent() where we have a pointer to the eviction > memcg. > > The flush call is sleepable, and cannot be made in an rcu read section. > Hence, minimize the rcu read section by also moving it into > workingset_test_recent(). Furthermore, instead of holding the rcu read > lock throughout workingset_test_recent(), only hold it briefly to get a > ref on the eviction memcg. This allows us to make the flush call after > we get the eviction memcg. > > As for workingset_refault(), nothing else there appears to be protected > by rcu. The memcg of the faulted folio (which is not necessarily the > same as the eviction memcg) is protected by the folio lock, which is > held from all callsites. Add a VM_BUG_ON() to make sure this doesn't > change from under us. > > No functional change intended. > > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > Tested-by: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx> Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
