From: Matthew Wilcox <mawil...@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 <mawil...@microsoft.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Vlastimil Babka <vba...@suse.cz>
---
mm/slab.c | 7 ++++---
mm/slab.h | 7 +++++++
mm/slob.c | 4 +++-
mm/slub.c | 5 +++--
4 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index 58c8cecc26ab..9ad85fd9fca8 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2661,6 +2661,7 @@ static struct page *cache_grow_begin(struct kmem_cache
*cachep,
invalid_mask, &invalid_mask, flags, &flags);
dump_stack();
}
+ BUG_ON(cachep->ctor && (flags & __GFP_ZERO));
local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
check_irq_off();
@@ -3325,7 +3326,7 @@ 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)
+ if (unlikely(flags & __GFP_ZERO) && ptr && slab_no_ctor(cachep))
memset(ptr, 0, cachep->object_size);
slab_post_alloc_hook(cachep, flags, 1, &ptr);
@@ -3382,7 +3383,7 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags,
unsigned long caller)
objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
prefetchw(objp);
- if (unlikely(flags & __GFP_ZERO) && objp)
+ if (unlikely(flags & __GFP_ZERO) && objp && slab_no_ctor(cachep))
memset(objp, 0, cachep->object_size);
slab_post_alloc_hook(cachep, flags, 1, &objp);
@@ -3589,7 +3590,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t
flags, size_t size,
cache_alloc_debugcheck_after_bulk(s, flags, size, p, _RET_IP_);
/* Clear memory outside IRQ disabled section */
- if (unlikely(flags & __GFP_ZERO))
+ if (unlikely(flags & __GFP_ZERO) && slab_no_ctor(s))
for (i = 0; i < size; i++)
memset(p[i], 0, s->object_size);
diff --git a/mm/slab.h b/mm/slab.h
index 3cd4677953c6..896818c7b30a 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -515,6 +515,13 @@ static inline void dump_unreclaimable_slab(void)
void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr);
+static inline bool slab_no_ctor(struct kmem_cache *s)
+{
+ if (IS_ENABLED(CONFIG_DEBUG_VM))
+ return !WARN_ON_ONCE(s->ctor);
+ return true;
+}
+
#ifdef CONFIG_SLAB_FREELIST_RANDOM
int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
gfp_t gfp);
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);
c->ctor(b);
+ }
kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
return b;
diff --git a/mm/slub.c b/mm/slub.c
index a28488643603..9f8f38a552e5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1576,6 +1576,7 @@ static struct page *allocate_slab(struct kmem_cache *s,
gfp_t flags, int node)
if (gfpflags_allow_blocking(flags))
local_irq_enable();
+ BUG_ON(s->ctor && (flags & __GFP_ZERO));
flags |= s->allocflags;
@@ -2725,7 +2726,7 @@ static __always_inline void *slab_alloc_node(struct
kmem_cache *s,
stat(s, ALLOC_FASTPATH);
}
- if (unlikely(gfpflags & __GFP_ZERO) && object)
+ if (unlikely(gfpflags & __GFP_ZERO) && object && slab_no_ctor(s))
memset(object, 0, s->object_size);
slab_post_alloc_hook(s, gfpflags, 1, &object);
@@ -3149,7 +3150,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t
flags, size_t size,
local_irq_enable();
/* Clear memory outside IRQ disabled fastpath loop */
- if (unlikely(flags & __GFP_ZERO)) {
+ if (unlikely(flags & __GFP_ZERO) && slab_no_ctor(s)) {
int j;
for (j = 0; j < i; j++)
--
2.16.3
