On Thu, Mar 28, 2024 at 03:02:54PM +0900, Damien Le Moal wrote: > But that is the problem: "checking the zone number again" means referencing > the > plug struct again from the lookup context while the last ref drop context is > freeing the plug. That race can be lost by the lookup context and lead to > referencing freed memory. So your solution would be OK for pre-allocated plugs > only.
Not if it is done in the Rcu critical section. > For kmalloc-ed() plugs, we still need the rcu grace period for free. So we > can only optimize for the pre-allocated plugs... Yes, bt it can use kfree_rcu which doesn't need the rcu_head in the zwplug.
