On 5/4/21 3:37 PM, Shakeel Butt wrote:
On Tue, May 4, 2021 at 6:24 AM Waiman Long <longman@xxxxxxxxxx> wrote:Since the merging of the new slab memory controller in v5.9, the page structure may store a pointer to obj_cgroup pointer array for slab pages. Currently, only the __GFP_ACCOUNT bit is masked off. However, the array is not readily reclaimable and doesn't need to come from the DMA buffer. So those GFP bits should be masked off as well. Do the flag bit clearing at memcg_alloc_page_obj_cgroups() to make sure that it is consistently applied no matter where it is called. Fixes: 286e04b8ed7a ("mm: memcg/slab: allocate obj_cgroups for non-root slab pages") Signed-off-by: Waiman Long <longman@xxxxxxxxxx> --- mm/memcontrol.c | 8 ++++++++ mm/slab.h | 1 - 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c100265dc393..5e3b4f23b830 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2863,6 +2863,13 @@ static struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg) } #ifdef CONFIG_MEMCG_KMEM +/* + * The allocated objcg pointers array is not accounted directly. + * Moreover, it should not come from DMA buffer and is not readily + * reclaimable. So those GFP bits should be masked off. + */ +#define OBJCGS_CLEAR_MASK (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT)What about __GFP_DMA32? Does it matter? It seems like DMA32 requests go to normal caches.
I included __GFP_DMA32 in my first draft patch. However, __GFP_DMA32 is not considered in determining the right kmalloc_type() (patch 2), so I took it out to make it consistent. I can certainly add it back.
Cheers, Longman
