Re: [PATCH v2] slub: do not merge cache if slub_debug contains a never-merge flag

[Pekka Enberg <penberg@iki.fi>]

On 12/26/2016 09:08 PM, Grygorii Maistrenko wrote:
> In case CONFIG_SLUB_DEBUG_ON=n, find_mergeable() gets debug features
> from commandline but never checks if there are features from the
> SLAB_NEVER_MERGE set.
> As a result selected by slub_debug caches are always mergeable if they
> have been created without a custom constructor set or without one of the
> SLAB_* debug features on.
>
> This moves the SLAB_NEVER_MERGE check below the flags update from
> commandline to make sure it won't merge the slab cache if one of the
> debug features is on.
>
> Signed-off-by: Grygorii Maistrenko <grygoriimkd@gmail.com>

Reviewed-by: Pekka Enberg <penberg@kernel.org>

> ---
>   mm/slab_common.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> New in v2:
> 	- (flags & SLAB_NEVER_MERGE) check is moved down below the flags update
> 	  as suggested by Christoph Lameter
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 329b03843863..a85a01439490 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -255,7 +255,7 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
>   {
>   	struct kmem_cache *s;
>   
> -	if (slab_nomerge || (flags & SLAB_NEVER_MERGE))
> +	if (slab_nomerge)
>   		return NULL;
>   
>   	if (ctor)
> @@ -266,6 +266,9 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
>   	size = ALIGN(size, align);
>   	flags = kmem_cache_flags(size, flags, name, NULL);
>   
> +	if (flags & SLAB_NEVER_MERGE)
> +		return NULL;
> +
>   	list_for_each_entry_reverse(s, &slab_caches, list) {
>   		if (slab_unmergeable(s))
>   			continue;

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>