From 3104138517fc66aad21f4a2487bb572e9fc2e3ec Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Thu, 13 Feb 2025 14:46:54 -0800 Subject: mm: make vma cache SLAB_TYPESAFE_BY_RCU 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. The only place this is not currently happening is in exit_mmap(). Add the missing vma_mark_detached() in exit_mmap(). Another issue which might trick lock_vma_under_rcu() during vma reuse is vm_area_dup(), which copies the entire content of the vma into a new one, overriding new vma's vm_refcnt and temporarily making it appear as attached. This might trick a racing lock_vma_under_rcu() to operate on a reused vma if it found the vma before it got reused. To prevent this situation, we should ensure that vm_refcnt stays at detached state (0) when it is copied and advances to attached state only after it is added into the vma tree. Introduce vm_area_init_from() which preserves new vma's vm_refcnt and use it in vm_area_dup(). Since all vmas are in detached state with no current readers when they are freed, lock_vma_under_rcu() will not be able to take vm_refcnt after vma got detached even if vma is reused. vma_mark_attached() in modified to include a release fence to ensure all stores to the vma happen before vm_refcnt gets initialized. Finally, make vm_area_cachep SLAB_TYPESAFE_BY_RCU. This will facilitate vm_area_struct reuse and will minimize the number of call_rcu() calls. [surenb@google.com: remove atomic_set_release() usage in tools/] Link: https://lkml.kernel.org/r/20250217054351.2973666-1-surenb@google.com Link: https://lkml.kernel.org/r/20250213224655.1680278-18-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka Tested-by: Shivank Garg Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com Cc: Christian Brauner Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: Hugh Dickins Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Klara Modin Cc: Liam R. Howlett Cc: Lokesh Gidra Cc: Lorenzo Stoakes Cc: Mateusz Guzik Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Oleg Nesterov Cc: Pasha Tatashin Cc: "Paul E . McKenney" Cc: Peter Xu Cc: Peter Zijlstra (Intel) Cc: Shakeel Butt Cc: Sourav Panda Cc: Wei Yang Cc: Will Deacon Cc: Heiko Carstens Cc: Stephen Rothwell Signed-off-by: Andrew Morton --- tools/include/linux/refcount.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'tools/include') diff --git a/tools/include/linux/refcount.h b/tools/include/linux/refcount.h index 36cb29bc57c2..1f30956e070d 100644 --- a/tools/include/linux/refcount.h +++ b/tools/include/linux/refcount.h @@ -60,6 +60,11 @@ static inline void refcount_set(refcount_t *r, unsigned int n) atomic_set(&r->refs, n); } +static inline void refcount_set_release(refcount_t *r, unsigned int n) +{ + atomic_set(&r->refs, n); +} + static inline unsigned int refcount_read(const refcount_t *r) { return atomic_read(&r->refs); -- cgit v1.2.3