Currently a non-slab kernel page which has been charged to a memory cgroup can't be mapped to userspace. The underlying reason is simple: PageKmemcg flag is defined as a page type (like buddy, offline, etc), so it takes a bit from a page->mapped counter. Pages with a type set can't be mapped to userspace. But in general the kmemcg flag has nothing to do with mapping to userspace. It only means that the page has been accounted by the page allocator, so it has to be properly uncharged on release. Some bpf maps are mapping the vmalloc-based memory to userspace, and their memory can't be accounted because of this implementation detail. This patchset removes this limitation by moving the PageKmemcg flag into one of the free bits of the page->mem_cgroup pointer. Also it formalizes accesses to the page->mem_cgroup and page->obj_cgroups using new helpers, adds several checks and removes a couple of obsolete functions. As the result the code became more robust with fewer open-coded bit tricks. v6: - removed a bogus change in the last commit - rebased to the current head with a minor fix v5: - added ~MEMCG_DATA_FLAGS_MASK to page_memcg_rcu(), by Michal - more cosmetic changes, by Johannes v4: - more cosmetic changes, by Johannes v3: - READ_ONCE() in page_memcg_rcu() and page_objcgs*(), by Johannes - many cosmetic changes and renamings, by Johannes v2: - fixed a bug in page_obj_cgroups_check() - moved some definitions between patches, by Shakeel - dropped the memcg flags mutual exclusion requirement, by Shakeel v1: - added and fixed comments, by Shakeel - added some VM_BUG_ON() checks - fixed the debug output format of page->memcg_data Roman Gushchin (4): mm: memcontrol: use helpers to read page's memcg data mm: memcontrol/slab: use helpers to access slab page's memcg_data mm: introduce page memcg flags mm: convert page kmemcg type to a page memcg flag fs/buffer.c | 2 +- fs/iomap/buffered-io.c | 2 +- include/linux/memcontrol.h | 215 +++++++++++++++++++++++++++++-- include/linux/mm.h | 22 ---- include/linux/mm_types.h | 5 +- include/linux/page-flags.h | 11 +- include/trace/events/writeback.h | 2 +- kernel/fork.c | 7 +- mm/debug.c | 4 +- mm/huge_memory.c | 4 +- mm/memcontrol.c | 139 +++++++++----------- mm/page_alloc.c | 8 +- mm/page_io.c | 6 +- mm/slab.h | 38 ++---- mm/workingset.c | 2 +- 15 files changed, 300 insertions(+), 167 deletions(-) -- 2.26.2
