On Wed, Feb 10, 2021 at 09:35:40PM -0800, Chris Goldsworthy wrote: > +/* These are used to control the BH LRU invalidation during page migration */ > +static struct cpumask lru_needs_invalidation; > +static bool bh_lru_disabled = false; As I asked before, what protects this on an SMP system? > @@ -1292,7 +1296,9 @@ static inline void check_irqs_on(void) > /* > * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is > * inserted at the front, and the buffer_head at the back if any is evicted. > - * Or, if already in the LRU it is moved to the front. > + * Or, if already in the LRU it is moved to the front. Note that if LRU is > + * disabled because of an ongoing page migration, we won't insert bh into the > + * LRU. And also, why do we need to do this? The page LRU has no equivalent mechanism to prevent new pages being added to the per-CPU LRU lists. If a BH has just been used, isn't that a strong hint that this page is a bad candidate for migration?
