On Wed, Dec 13, 2023 at 8:27 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Wed, Dec 13, 2023 at 08:24:04AM -0800, Yosry Ahmed wrote: > > I doubt an extra compound_head() will matter in that path, but if you > > feel strongly about it that's okay. It's a nice cleanup that's all. > > i don't even understand why you think it's a nice cleanup. free_pages_prepare() is directly calling __memcg_kmem_uncharge_page() instead of memcg_kmem_uncharge_page(), and open-coding checks that already exist in both of them to avoid the unnecessary function call if possible. I think this should be the job of memcg_kmem_uncharge_page(), but it's currently missing the PageMemcgKmem() check (which is in __memcg_kmem_uncharge_page()). So I think moving that check to the wrapper allows free_pages_prepare() to call memcg_kmem_uncharge_page() and without worrying about those memcg-specific checks.
