89  * Each wb (bdi_writeback) can perform writeback operations, is measured
91  * (bdi_writeback) is served by its embedded bdi->wb.
95  * memcg - blkcg combination can be served by its own wb by assigning a
96  * dedicated wb to each memcg, which enables isolation across different
100  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
103  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
105  * that a new wb for the combination can be created.
151 	struct percpu_ref refcnt;	/* used only for !root wb's */
183 	struct bdi_writeback wb;  /* the root writeback info for this bdi */  member
187 	struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
219  * wb_tryget - try to increment a wb's refcount
220  * @wb: bdi_writeback to get
222 static inline bool wb_tryget(struct bdi_writeback *wb)  in wb_tryget()  argument
224 	if (wb != &wb->bdi->wb)  in wb_tryget()
225 		return percpu_ref_tryget(&wb->refcnt);  in wb_tryget()
230  * wb_get - increment a wb's refcount
231  * @wb: bdi_writeback to get
233 static inline void wb_get(struct bdi_writeback *wb)  in wb_get()  argument
235 	if (wb != &wb->bdi->wb)  in wb_get()
236 		percpu_ref_get(&wb->refcnt);  in wb_get()
240  * wb_put - decrement a wb's refcount
241  * @wb: bdi_writeback to put
243 static inline void wb_put(struct bdi_writeback *wb)  in wb_put()  argument
245 	if (WARN_ON_ONCE(!wb->bdi)) {  in wb_put()
253 	if (wb != &wb->bdi->wb)  in wb_put()
254 		percpu_ref_put(&wb->refcnt);  in wb_put()
258  * wb_dying - is a wb dying?
259  * @wb: bdi_writeback of interest
261  * Returns whether @wb is unlinked and being drained.
263 static inline bool wb_dying(struct bdi_writeback *wb)  in wb_dying()  argument
265 	return percpu_ref_is_dying(&wb->refcnt);  in wb_dying()
270 static inline bool wb_tryget(struct bdi_writeback *wb)  in wb_tryget()  argument
275 static inline void wb_get(struct bdi_writeback *wb)  in wb_get()  argument
279 static inline void wb_put(struct bdi_writeback *wb)  in wb_put()  argument
283 static inline bool wb_dying(struct bdi_writeback *wb)  in wb_dying()  argument