On 12/26/24 18:07, Suren Baghdasaryan wrote: > To enable SLAB_TYPESAFE_BY_RCU for vma cache we need to ensure that > object reuse before RCU grace period is over will be detected by > lock_vma_under_rcu(). Current checks are sufficient as long as vma > is detached before it is freed. Implement this guarantee by calling > vma_ensure_detached() before vma is freed and make vm_area_cachep > SLAB_TYPESAFE_BY_RCU. This will facilitate vm_area_struct reuse and > will minimize the number of call_rcu() calls. > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> I've noticed vm_area_dup() went back to the approach of "we memcpy everything including vma_lock and detached (now the vm_refcnt) followed by a vma_init_lock(..., true) that does refcount_set(&vma->vm_refcnt, 0); Is that now safe against a racing lock_vma_under_rcu()? I think it's not?
