On 7/21/20 5:28 AM, js1304@gmail.com wrote:
From: Joonsoo Kim iamjoonsoo.kim@lge.com
Currently, memalloc_nocma_{save/restore} API that prevents CMA area in page allocation is implemented by using current_gfp_context(). However, there are two problems of this implementation.
First, this doesn't work for allocation fastpath. In the fastpath, original gfp_mask is used since current_gfp_context() is introduced in order to control reclaim and it is on slowpath. So, CMA area can be allocated through the allocation fastpath even if memalloc_nocma_{save/restore} APIs are used. Currently, there is just one user for these APIs and it has a fallback method to prevent actual problem. Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect to exclude the memory on the ZONE_MOVABLE for allocation target.
To fix these problems, this patch changes the implementation to exclude CMA area in page allocation. Main point of this change is using the alloc_flags. alloc_flags is mainly used to control allocation so it fits for excluding CMA area in allocation.
Moreover, the ALLOC_CMA flag already exists for exactly this purpose.
Fixes: d7fefcc8de91 (mm/cma: add PF flag to force non cma alloc) Cc: stable@vger.kernel.org Signed-off-by: Joonsoo Kim iamjoonsoo.kim@lge.com
Reviewed-by: Vlastimil Babka vbabka@suse.cz
Thanks!