From 5f0d5a3ae7cff0d7fa943c199c3a2e44f23e1fac Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 18 Jan 2017 02:53:44 -0800 Subject: mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU A group of Linux kernel hackers reported chasing a bug that resulted from their assumption that SLAB_DESTROY_BY_RCU provided an existence guarantee, that is, that no block from such a slab would be reallocated during an RCU read-side critical section. Of course, that is not the case. Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire slab of blocks. However, there is a phrase for this, namely "type safety". This commit therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order to avoid future instances of this sort of confusion. Signed-off-by: Paul E. McKenney Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Acked-by: Johannes Weiner Acked-by: Vlastimil Babka [ paulmck: Add comments mentioning the old name, as requested by Eric Dumazet, in order to help people familiar with the old name find the new one. ] Acked-by: David Rientjes --- mm/slab.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'mm/slab.c') diff --git a/mm/slab.c b/mm/slab.c index 807d86c76908..93c827864862 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1728,7 +1728,7 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page) freelist = page->freelist; slab_destroy_debugcheck(cachep, page); - if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) + if (unlikely(cachep->flags & SLAB_TYPESAFE_BY_RCU)) call_rcu(&page->rcu_head, kmem_rcu_free); else kmem_freepages(cachep, page); @@ -1924,7 +1924,7 @@ static bool set_objfreelist_slab_cache(struct kmem_cache *cachep, cachep->num = 0; - if (cachep->ctor || flags & SLAB_DESTROY_BY_RCU) + if (cachep->ctor || flags & SLAB_TYPESAFE_BY_RCU) return false; left = calculate_slab_order(cachep, size, @@ -2030,7 +2030,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) if (size < 4096 || fls(size - 1) == fls(size-1 + REDZONE_ALIGN + 2 * sizeof(unsigned long long))) flags |= SLAB_RED_ZONE | SLAB_STORE_USER; - if (!(flags & SLAB_DESTROY_BY_RCU)) + if (!(flags & SLAB_TYPESAFE_BY_RCU)) flags |= SLAB_POISON; #endif #endif -- cgit v1.2.3-70-g09d2