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| author | Tejun Heo <tj@kernel.org> | 2015-10-02 14:47:05 -0400 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-10-12 10:31:12 -0600 |
| commit | b817525a4a80c04e4ca44192d97a1ffa9f2be572 (patch) | |
| tree | 70f7b2766d25209f6ca2d1c3370193562aded622 /include/linux/backing-dev-defs.h | |
| parent | 6fdf860f15d4a6be8f0947bad608d687fe0c7af7 (diff) | |
| download | lwn-b817525a4a80c04e4ca44192d97a1ffa9f2be572.tar.gz lwn-b817525a4a80c04e4ca44192d97a1ffa9f2be572.zip | |
writeback: bdi_writeback iteration must not skip dying ones
bdi_for_each_wb() is used in several places to wake up or issue
writeback work items to all wb's (bdi_writeback's) on a given bdi.
The iteration is performed by walking bdi->cgwb_tree; however, the
tree only indexes wb's which are currently active.
For example, when a memcg gets associated with a different blkcg, the
old wb is removed from the tree so that the new one can be indexed.
The old wb starts dying from then on but will linger till all its
inodes are drained. As these dying wb's may still host dirty inodes,
writeback operations which affect all wb's must include them.
bdi_for_each_wb() skipping dying wb's led to sync(2) missing and
failing to sync the inodes belonging to those wb's.
This patch adds a RCU protected @bdi->wb_list which lists all wb's
beloinging to that bdi. wb's are added on creation and removed on
release rather than on the start of destruction. bdi_for_each_wb()
usages are replaced with list_for_each[_continue]_rcu() iterations
over @bdi->wb_list and bdi_for_each_wb() and its helpers are removed.
v2: Updated as per Jan. last_wb ref leak in bdi_split_work_to_wbs()
fixed and unnecessary list head severing in cgwb_bdi_destroy()
removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Artem Bityutskiy <dedekind1@gmail.com>
Fixes: ebe41ab0c79d ("writeback: implement bdi_for_each_wb()")
Link: http://lkml.kernel.org/g/1443012552.19983.209.camel@gmail.com
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include/linux/backing-dev-defs.h')
| -rw-r--r-- | include/linux/backing-dev-defs.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index a23209b43842..1b4d69f68c33 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -116,6 +116,8 @@ struct bdi_writeback { struct list_head work_list; struct delayed_work dwork; /* work item used for writeback */ + struct list_head bdi_node; /* anchored at bdi->wb_list */ + #ifdef CONFIG_CGROUP_WRITEBACK struct percpu_ref refcnt; /* used only for !root wb's */ struct fprop_local_percpu memcg_completions; @@ -150,6 +152,7 @@ struct backing_dev_info { atomic_long_t tot_write_bandwidth; struct bdi_writeback wb; /* the root writeback info for this bdi */ + struct list_head wb_list; /* list of all wbs */ #ifdef CONFIG_CGROUP_WRITEBACK struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */ struct rb_root cgwb_congested_tree; /* their congested states */ |