84  * Each wb (bdi_writeback) can perform writeback operations, is measured
86  * (bdi_writeback) is served by its embedded bdi->wb.
90  * memcg - blkcg combination can be served by its own wb by assigning a
91  * dedicated wb to each memcg, which enables isolation across different
95  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
98  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
100  * that a new wb for the combination can be created.
147 	struct percpu_ref refcnt;	/* used only for !root wb's */
186 	struct bdi_writeback wb;  /* the root writeback info for this bdi */  member
190 	struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
214  * wb_tryget - try to increment a wb's refcount
215  * @wb: bdi_writeback to get
217 static inline bool wb_tryget(struct bdi_writeback *wb)  in wb_tryget()  argument
219 	if (wb != &wb->bdi->wb)  in wb_tryget()
220 		return percpu_ref_tryget(&wb->refcnt);  in wb_tryget()
225  * wb_get - increment a wb's refcount
226  * @wb: bdi_writeback to get
228 static inline void wb_get(struct bdi_writeback *wb)  in wb_get()  argument
230 	if (wb != &wb->bdi->wb)  in wb_get()
231 		percpu_ref_get(&wb->refcnt);  in wb_get()
235  * wb_put - decrement a wb's refcount
236  * @wb: bdi_writeback to put
239 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)  in wb_put_many()  argument
241 	if (WARN_ON_ONCE(!wb->bdi)) {  in wb_put_many()
249 	if (wb != &wb->bdi->wb)  in wb_put_many()
250 		percpu_ref_put_many(&wb->refcnt, nr);  in wb_put_many()
254  * wb_put - decrement a wb's refcount
255  * @wb: bdi_writeback to put
257 static inline void wb_put(struct bdi_writeback *wb)  in wb_put()  argument
259 	wb_put_many(wb, 1);  in wb_put()
263  * wb_dying - is a wb dying?
264  * @wb: bdi_writeback of interest
266  * Returns whether @wb is unlinked and being drained.
268 static inline bool wb_dying(struct bdi_writeback *wb)  in wb_dying()  argument
270 	return percpu_ref_is_dying(&wb->refcnt);  in wb_dying()
275 static inline bool wb_tryget(struct bdi_writeback *wb)  in wb_tryget()  argument
280 static inline void wb_get(struct bdi_writeback *wb)  in wb_get()  argument
284 static inline void wb_put(struct bdi_writeback *wb)  in wb_put()  argument
288 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)  in wb_put_many()  argument
292 static inline bool wb_dying(struct bdi_writeback *wb)  in wb_dying()  argument