From 1ced953b17bfaf54ec1499f8bbfdf31ab36453af Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 8 Jul 2014 18:02:57 -0400 Subject: [PATCH] blkcg, memcg: make blkcg depend on memcg on the default hierarchy Currently, the blkio subsystem attributes all of writeback IOs to the root. One of the issues is that there's no way to tell who originated a writeback IO from block layer. Those IOs are usually issued asynchronously from a task which didn't have anything to do with actually generating the dirty pages. The memory subsystem, when enabled, already keeps track of the ownership of each dirty page and it's desirable for blkio to piggyback instead of adding its own per-page tag. cgroup now has a mechanism to express such dependency - cgroup_subsys->depends_on. This patch declares that blkcg depends on memcg so that memcg is enabled automatically on the default hierarchy when available. Future changes will make blkcg map the memcg tag to find out the cgroup to blame for writeback IOs. As this means that a memcg may be made invisible, this patch also implements css_reset() for memcg which resets its basic configurations. This implementation will probably need to be expanded to cover other states which are used in the default hierarchy. v2: blkcg's dependency on memcg is wrapped with CONFIG_MEMCG to avoid build failure. Reported by kbuild test robot. Signed-off-by: Tejun Heo Acked-by: Li Zefan Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Vivek Goyal Cc: Jens Axboe --- block/blk-cgroup.c | 8 ++++++++ mm/memcontrol.c | 24 ++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 069bc202ffe3..63c3cd454d1e 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -925,6 +925,14 @@ struct cgroup_subsys blkio_cgrp_subsys = { .css_free = blkcg_css_free, .can_attach = blkcg_can_attach, .base_cftypes = blkcg_files, +#ifdef CONFIG_MEMCG + /* + * This ensures that, if available, memcg is automatically enabled + * together on the default hierarchy so that the owner cgroup can + * be retrieved from writeback pages. + */ + .depends_on = 1 << memory_cgrp_id, +#endif }; EXPORT_SYMBOL_GPL(blkio_cgrp_subsys); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a2c7bcb0e6eb..db536e90c8ee 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6407,6 +6407,29 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css) __mem_cgroup_free(memcg); } +/** + * mem_cgroup_css_reset - reset the states of a mem_cgroup + * @css: the target css + * + * Reset the states of the mem_cgroup associated with @css. This is + * invoked when the userland requests disabling on the default hierarchy + * but the memcg is pinned through dependency. The memcg should stop + * applying policies and should revert to the vanilla state as it may be + * made visible again. + * + * The current implementation only resets the essential configurations. + * This needs to be expanded to cover all the visible parts. + */ +static void mem_cgroup_css_reset(struct cgroup_subsys_state *css) +{ + struct mem_cgroup *memcg = mem_cgroup_from_css(css); + + mem_cgroup_resize_limit(memcg, ULLONG_MAX); + mem_cgroup_resize_memsw_limit(memcg, ULLONG_MAX); + memcg_update_kmem_limit(memcg, ULLONG_MAX); + res_counter_set_soft_limit(&memcg->res, ULLONG_MAX); +} + #ifdef CONFIG_MMU /* Handlers for move charge at task migration. */ #define PRECHARGE_COUNT_AT_ONCE 256 @@ -7019,6 +7042,7 @@ struct cgroup_subsys memory_cgrp_subsys = { .css_online = mem_cgroup_css_online, .css_offline = mem_cgroup_css_offline, .css_free = mem_cgroup_css_free, + .css_reset = mem_cgroup_css_reset, .can_attach = mem_cgroup_can_attach, .cancel_attach = mem_cgroup_cancel_attach, .attach = mem_cgroup_move_task, -- 2.30.2