slab: __GFP_ZERO is incompatible with a constructor
__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.
Link: http://lkml.kernel.org/r/20180412191322.GA21205@bombadil.infradead.org
Fixes: d07dbea46405 ("Slab allocators: support __GFP_ZERO in all allocators")
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slob.c b/mm/slob.c
index 623e8a5..307c2c9 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -555,8 +555,10 @@ 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);
c->ctor(b);
+ }
kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
return b;