On Tue, Sep 22, 2020 at 1:37 PM Roman Gushchin <guro@xxxxxx> wrote: > > PageKmemcg flag is currently defined as a page type (like buddy, > offline, table and guard). Semantically it means that the page > was accounted as a kernel memory by the page allocator and has > to be uncharged on the release. > > As a side effect of defining the flag as a page type, the accounted > page can't be mapped to userspace (look at page_has_type() and > comments above). In particular, this blocks the accounting of > vmalloc-backed memory used by some bpf maps, because these maps > do map the memory to userspace. > > One option is to fix it by complicating the access to page->mapcount, > which provides some free bits for page->page_type. > > But it's way better to move this flag into page->memcg_data flags. > Indeed, the flag makes no sense without enabled memory cgroups > and memory cgroup pointer set in particular. > > This commit replaces PageKmemcg() and __SetPageKmemcg() with > PageMemcgKmem() and SetPageMemcgKmem(). __ClearPageKmemcg() > can be simple deleted because clear_page_mem_cgroup() already > does the job. > > As a bonus, on !CONFIG_MEMCG build the PageMemcgKmem() check will > be compiled out. > > Signed-off-by: Roman Gushchin <guro@xxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
