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/slob.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'mm/slob.c') diff --git a/mm/slob.c b/mm/slob.c index eac04d4357ec..1bae78d71096 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -126,7 +126,7 @@ static inline void clear_slob_page_free(struct page *sp) /* * struct slob_rcu is inserted at the tail of allocated slob blocks, which - * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free + * were created with a SLAB_TYPESAFE_BY_RCU slab. slob_rcu is used to free * the block using call_rcu. */ struct slob_rcu { @@ -524,7 +524,7 @@ EXPORT_SYMBOL(ksize); int __kmem_cache_create(struct kmem_cache *c, unsigned long flags) { - if (flags & SLAB_DESTROY_BY_RCU) { + if (flags & SLAB_TYPESAFE_BY_RCU) { /* leave room for rcu footer at the end of object */ c->size += sizeof(struct slob_rcu); } @@ -598,7 +598,7 @@ static void kmem_rcu_free(struct rcu_head *head) void kmem_cache_free(struct kmem_cache *c, void *b) { kmemleak_free_recursive(b, c->flags); - if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) { + if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) { struct slob_rcu *slob_rcu; slob_rcu = b + (c->size - sizeof(struct slob_rcu)); slob_rcu->size = c->size; -- cgit v1.2.3