slab: too much allocated in bootstrap head arrays?

PATCH roel 2 participants 2 messages Dec 12, 2011 – Dec 13, 2011 Memory management

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roel

author

2011-12-12 22:16 UTC #0 lore raw

In mm/slab.c kmem_cache_init() at /* 4) Replace the bootstrap head arrays */ it kmallocs *ptr and memcpy's with sizeof(struct arraycache_init). Is this correct or should it maybe be with sizeof(struct arraycache) instead?

Please review, i.e. this change:
---
It appears we allocated and copied too much.

Signed-off-by Roel Kluin <[email protected]>

---
 mm/slab.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

mm/slab.c +4 -4

index 83311c9a..6978cbf 100644
@@ -1617,11 +1617,11 @@ void __init kmem_cache_init(void)
 	{
 		struct array_cache *ptr;
 
-		ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
+		ptr = kmalloc(sizeof(struct arraycache), GFP_NOWAIT);
 
 		BUG_ON(cpu_cache_get(&cache_cache) != &initarray_cache.cache);
 		memcpy(ptr, cpu_cache_get(&cache_cache),
-		       sizeof(struct arraycache_init));
+		       sizeof(struct arraycache));
 		/*
 		 * Do not assume that spinlocks can be initialized via memcpy:
 		 */

@@ -1629,12 +1629,12 @@ void __init kmem_cache_init(void)
 
 		cache_cache.array[smp_processor_id()] = ptr;
 
-		ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
+		ptr = kmalloc(sizeof(struct arraycache), GFP_NOWAIT);
 
 		BUG_ON(cpu_cache_get(malloc_sizes[INDEX_AC].cs_cachep)
 		       != &initarray_generic.cache);
 		memcpy(ptr, cpu_cache_get(malloc_sizes[INDEX_AC].cs_cachep),
-		       sizeof(struct arraycache_init));
+		       sizeof(struct arraycache));
 		/*
 		 * Do not assume that spinlocks can be initialized via memcpy:
 		 */

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Christoph Lameter

2011-12-13 16:15 UTC #1 lore raw

Quoted 3 lines · roel

In mm/slab.c kmem_cache_init() at /* 4) Replace the bootstrap head arrays */ it kmallocs *ptr and memcpy's with sizeof(struct arraycache_init). Is this correct or should it maybe be with sizeof(struct arraycache) instead?

Allocating with sizeof(struct arraycache) will only allocate the header of the array cache and not reserve space for the pointers that are part of it. It is always wrong.

Look at alloc_arraycache() for the proper way to use struct arraycache to calculate the number of bytes needed.