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Commit 128227e7 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
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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: d07dbea4 ("Slab allocators: support __GFP_ZERO in all allocators")
Signed-off-by: default avatarMatthew Wilcox <mawilcox@microsoft.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e56ee574

mm/slab.c

+2 −0
Original line number Diff line number Diff line
@@ -2665,6 +2665,7 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep, 
				invalid_mask, &invalid_mask, flags, &flags);

		dump_stack();

	}

	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));

	local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);



	check_irq_off();
@@ -3071,6 +3072,7 @@ static inline void cache_alloc_debugcheck_before(struct kmem_cache *cachep, 
static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,

				gfp_t flags, void *objp, unsigned long caller)

{

	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));

	if (!objp)

		return objp;

	if (cachep->flags & SLAB_POISON) {

mm/slob.c

+3 −1
Original line number Diff line number Diff line
@@ -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;

mm/slub.c

+2 −0
Original line number Diff line number Diff line
@@ -2444,6 +2444,8 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags, 
	struct kmem_cache_cpu *c = *pc;

	struct page *page;



	WARN_ON_ONCE(s->ctor && (flags & __GFP_ZERO));



	freelist = get_partial(s, flags, node, c);



	if (freelist)