On Thu, Jan 24, 2013 at 10:50:09PM -0500, CAI Qian wrote:
> This is for stable-3.7.y only and this problem has already been solved
> in mainline through some slab/slub re-work which isn't suitable to
> backport here. See create_kmalloc_cache() in mm/slab_common.c there.
>
> commit cce89f4f6911286500cf7be0363f46c9b0a12ce0('Move kmem_cache
> refcounting to common code') moves some refcount manipulation code to
> common code. Unfortunately, it also removed refcount assignment for
> kmalloc_caches. So, kmalloc_caches's refcount is initially 0.
> This makes erroneous situation.
>
> Paul Hargrove report that when he create a 8-byte kmem_cache and
> destory it, he encounter below message.
> 'Objects remaining in kmalloc-8 on kmem_cache_close()'
>
> 8-byte kmem_cache merge with 8-byte kmalloc cache and refcount is
> increased by one. So, resulting refcount is 1. When destroy it, it hit
> refcount = 0, then kmem_cache_close() is executed and error message is
> printed.
>
> This patch assign initial refcount 1 to kmalloc_caches, so fix this
> erroneous situation.
>
> Cc: <[email protected]> # v3.7
> Cc: Christoph Lameter <[email protected]>
> Reported-by: Paul Hargrove <[email protected]>
> Signed-off-by: Joonsoo Kim <[email protected]>
> Signed-off-by: CAI Qian <[email protected]>
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a0d6984..321afab 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3279,6 +3279,7 @@ static struct kmem_cache *__init
> create_kmalloc_cache(const char *name,
> if (kmem_cache_open(s, flags))
> goto panic;
>
> + s->refcount = 1;
> list_add(&s->list, &slab_caches);
> return s;
> --
Your email client dropped the last line of the patch, so I had to
hand-edit it.
Ugh, please fix your email client, again...
greg k-h
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