On 04/10/2018 02:53 PM, Matthew Wilcox wrote:
From: Matthew Wilcox mawilcox@microsoft.com
__GFP_ZERO requests that the object be initialised to all-zeroes, while the purpose of a constructor is to initialise an object to a particular pattern. We cannot do both. Add a warning to catch any users who mistakenly pass a __GFP_ZERO flag when allocating a slab with a constructor.
Fixes: d07dbea46405 ("Slab allocators: support __GFP_ZERO in all allocators") Signed-off-by: Matthew Wilcox mawilcox@microsoft.com Cc: stable@vger.kernel.org
It doesn't fix any known problem, does it? Then the stable tag seems too much IMHO. Especially for fixing a 2007 commit.
Otherwise Acked-by: Vlastimil Babka vbabka@suse.cz
mm/slab.c | 6 ++++-- mm/slob.c | 4 +++- mm/slub.c | 6 ++++-- 3 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c index 38d3f4fd17d7..8b2cb7db85db 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3313,8 +3313,10 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid, local_irq_restore(save_flags); ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller);
- if (unlikely(flags & __GFP_ZERO) && ptr)
memset(ptr, 0, cachep->object_size);
- if (unlikely(flags & __GFP_ZERO) && ptr) {
if (!WARN_ON_ONCE(cachep->ctor))memset(ptr, 0, cachep->object_size);- }
slab_post_alloc_hook(cachep, flags, 1, &ptr); return ptr; diff --git a/mm/slob.c b/mm/slob.c index 1a46181b675c..958173fd7c24 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -556,8 +556,10 @@ static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node) flags, node); }
- if (b && c->ctor)
- if (b && c->ctor) {
WARN_ON_ONCE(flags & __GFP_ZERO);- }
kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags); return b; diff --git a/mm/slub.c b/mm/slub.c index 9e1100f9298f..0f55f0a0dcaa 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2714,8 +2714,10 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, stat(s, ALLOC_FASTPATH); }
- if (unlikely(gfpflags & __GFP_ZERO) && object)
memset(object, 0, s->object_size);
- if (unlikely(gfpflags & __GFP_ZERO) && object) {
if (!WARN_ON_ONCE(s->ctor))memset(object, 0, s->object_size);- }
slab_post_alloc_hook(s, gfpflags, 1, &object);