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authorTejun Heo <tj@kernel.org>2015-05-22 17:13:37 -0400
committerJens Axboe <axboe@fb.com>2015-06-02 08:33:35 -0600
commit52ebea749aaed195245701a8f90a23d672c7a933 (patch)
tree5fac5f82f94b64a9cbcb65a99f4cddf4b13456e2 /include/linux/blk-cgroup.h
parent89e9b9e07a390c50980d10aa37a04631db5a23ab (diff)
writeback: make backing_dev_info host cgroup-specific bdi_writebacks
For the planned cgroup writeback support, on each bdi (backing_dev_info), each memcg will be served by a separate wb (bdi_writeback). This patch updates bdi so that a bdi can host multiple wbs (bdi_writebacks). On the default hierarchy, blkcg implicitly enables memcg. This allows using memcg's page ownership for attributing writeback IOs, and every memcg - blkcg combination can be served by its own wb by assigning a dedicated wb to each memcg. This means that there may be multiple wb's of a bdi mapped to the same blkcg. As congested state is per blkcg - bdi combination, those wb's should share the same congested state. This is achieved by tracking congested state via bdi_writeback_congested structs which are keyed by blkcg. bdi->wb remains unchanged and will keep serving the root cgroup. cgwb's (cgroup wb's) for non-root cgroups are created on-demand or looked up while dirtying an inode according to the memcg of the page being dirtied or current task. Each cgwb is indexed on bdi->cgwb_tree by its memcg id. Once an inode is associated with its wb, it can be retrieved using inode_to_wb(). Currently, none of the filesystems has FS_CGROUP_WRITEBACK and all pages will keep being associated with bdi->wb. v3: inode_attach_wb() in account_page_dirtied() moved inside mapping_cap_account_dirty() block where it's known to be !NULL. Also, an unnecessary NULL check before kfree() removed. Both detected by the kbuild bot. v2: Updated so that wb association is per inode and wb is per memcg rather than blkcg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: kbuild test robot <fengguang.wu@intel.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include/linux/blk-cgroup.h')
-rw-r--r--include/linux/blk-cgroup.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 4dc643f2046e..3033eb173eb4 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -53,6 +53,10 @@ struct blkcg {
/* TODO: per-policy storage in blkcg */
unsigned int cfq_weight; /* belongs to cfq */
unsigned int cfq_leaf_weight;
+
+#ifdef CONFIG_CGROUP_WRITEBACK
+ struct list_head cgwb_list;
+#endif
};
struct blkg_stat {