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mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU

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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 <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
[ 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 <[email protected]>
This commit is contained in:
Paul E. McKenney 2017-01-18 02:53:44 -08:00
commit 5f0d5a3ae7
30 changed files with 57 additions and 54 deletions
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6
mm/kasan/kasan.c
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@ -413,7 +413,7 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
*size += sizeof(struct kasan_alloc_meta);
/* Add free meta. */
if (cache->flags & SLAB_DESTROY_BY_RCU || cache->ctor ||
if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
cache->object_size < sizeof(struct kasan_free_meta)) {
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
@ -561,7 +561,7 @@ static void kasan_poison_slab_free(struct kmem_cache *cache, void *object)
unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
/* RCU slabs could be legally used after free within the RCU period */
if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
return;
kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
@ -572,7 +572,7 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object)
s8 shadow_byte;
/* RCU slabs could be legally used after free within the RCU period */
if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
return false;
shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));