Roman Gushchin bcfe06bf26 mm: memcontrol: Use helpers to read page's memcg data ... Patch series "mm: allow mapping accounted kernel pages to userspace", v6. 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. This patch (of 4): Currently there are many open-coded reads of the page->mem_cgroup pointer, as well as a couple of read helpers, which are barely used. It creates an obstacle on a way to reuse some bits of the pointer for storing additional bits of information. In fact, we already do this for slab pages, where the last bit indicates that a pointer has an attached vector of objcg pointers instead of a regular memcg pointer. This commits uses 2 existing helpers and introduces a new helper to converts all read sides to calls of these helpers: struct mem_cgroup *page_memcg(struct page *page); struct mem_cgroup *page_memcg_rcu(struct page *page); struct mem_cgroup *page_memcg_check(struct page *page); page_memcg_check() is intended to be used in cases when the page can be a slab page and have a memcg pointer pointing at objcg vector. It does check the lowest bit, and if set, returns NULL. page_memcg() contains a VM_BUG_ON_PAGE() check for the page not being a slab page. To make sure nobody uses a direct access, struct page's mem_cgroup/obj_cgroups is converted to unsigned long memcg_data. Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com		2020-12-02 18:28:05 -08:00
..
apply.c	iomap: Make sure iomap_end is called after iomap_begin	2020-07-06 10:49:27 -07:00
buffered-io.c	mm: memcontrol: Use helpers to read page's memcg data	2020-12-02 18:28:05 -08:00
direct-io.c	iomap: Call inode_dio_end() before generic_write_sync()	2020-09-28 08:51:08 -07:00
fiemap.c	fs: handle FIEMAP_FLAG_SYNC in fiemap_prep	2020-06-03 23:16:55 -04:00
Makefile	iomap: lift common tracing code from xfs to iomap	2019-10-21 08:51:59 -07:00
seek.c	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
swapfile.c	iomap: use a srcmap for a read-modify-write I/O	2019-10-21 08:51:59 -07:00
trace.c	iomap: lift common tracing code from xfs to iomap	2019-10-21 08:51:59 -07:00
trace.h	iomap: fall back to buffered writes for invalidation failures	2020-08-05 09:24:16 -07:00