writeback: Separate out wb_get_lookup() from wb_get_create()

Separate out wb_get_lookup() which doesn't try to create one if there
isn't already one from wb_get_create().  This will be used by later
patches.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 84cdcfbc763f..97967ce06de3 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -230,6 +230,8 @@ static inline int bdi_sched_wait(void *word)
 struct bdi_writeback_congested *
 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
 void wb_congested_put(struct bdi_writeback_congested *congested);
+struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
+                                    struct cgroup_subsys_state *memcg_css);
 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
                                     struct cgroup_subsys_state *memcg_css,
                                     gfp_t gfp);