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diff --git a/block/blk-throttle.h b/block/blk-throttle.h
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+#ifndef BLK_THROTTLE_H
+#define BLK_THROTTLE_H
+
+#include "blk-cgroup-rwstat.h"
+
+/*
+ * To implement hierarchical throttling, throtl_grps form a tree and bios
+ * are dispatched upwards level by level until they reach the top and get
+ * issued. When dispatching bios from the children and local group at each
+ * level, if the bios are dispatched into a single bio_list, there's a risk
+ * of a local or child group which can queue many bios at once filling up
+ * the list starving others.
+ *
+ * To avoid such starvation, dispatched bios are queued separately
+ * according to where they came from. When they are again dispatched to
+ * the parent, they're popped in round-robin order so that no single source
+ * hogs the dispatch window.
+ *
+ * throtl_qnode is used to keep the queued bios separated by their sources.
+ * Bios are queued to throtl_qnode which in turn is queued to
+ * throtl_service_queue and then dispatched in round-robin order.
+ *
+ * It's also used to track the reference counts on blkg's. A qnode always
+ * belongs to a throtl_grp and gets queued on itself or the parent, so
+ * incrementing the reference of the associated throtl_grp when a qnode is
+ * queued and decrementing when dequeued is enough to keep the whole blkg
+ * tree pinned while bios are in flight.
+ */
+struct throtl_qnode {
+ struct list_head node; /* service_queue->queued[] */
+ struct bio_list bios; /* queued bios */
+ struct throtl_grp *tg; /* tg this qnode belongs to */
+};
+
+struct throtl_service_queue {
+ struct throtl_service_queue *parent_sq; /* the parent service_queue */
+
+ /*
+ * Bios queued directly to this service_queue or dispatched from
+ * children throtl_grp's.
+ */
+ struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
+ unsigned int nr_queued[2]; /* number of queued bios */
+
+ /*
+ * RB tree of active children throtl_grp's, which are sorted by
+ * their ->disptime.
+ */
+ struct rb_root_cached pending_tree; /* RB tree of active tgs */
+ unsigned int nr_pending; /* # queued in the tree */
+ unsigned long first_pending_disptime; /* disptime of the first tg */
+ struct timer_list pending_timer; /* fires on first_pending_disptime */
+};
+
+enum {
+ LIMIT_LOW,
+ LIMIT_MAX,
+ LIMIT_CNT,
+};
+
+struct throtl_grp {
+ /* must be the first member */
+ struct blkg_policy_data pd;
+
+ /* active throtl group service_queue member */
+ struct rb_node rb_node;
+
+ /* throtl_data this group belongs to */
+ struct throtl_data *td;
+
+ /* this group's service queue */
+ struct throtl_service_queue service_queue;
+
+ /*
+ * qnode_on_self is used when bios are directly queued to this
+ * throtl_grp so that local bios compete fairly with bios
+ * dispatched from children. qnode_on_parent is used when bios are
+ * dispatched from this throtl_grp into its parent and will compete
+ * with the sibling qnode_on_parents and the parent's
+ * qnode_on_self.
+ */
+ struct throtl_qnode qnode_on_self[2];
+ struct throtl_qnode qnode_on_parent[2];
+
+ /*
+ * Dispatch time in jiffies. This is the estimated time when group
+ * will unthrottle and is ready to dispatch more bio. It is used as
+ * key to sort active groups in service tree.
+ */
+ unsigned long disptime;
+
+ unsigned int flags;
+
+ /* are there any throtl rules between this group and td? */
+ bool has_rules[2];
+
+ /* internally used bytes per second rate limits */
+ uint64_t bps[2][LIMIT_CNT];
+ /* user configured bps limits */
+ uint64_t bps_conf[2][LIMIT_CNT];
+
+ /* internally used IOPS limits */
+ unsigned int iops[2][LIMIT_CNT];
+ /* user configured IOPS limits */
+ unsigned int iops_conf[2][LIMIT_CNT];
+
+ /* Number of bytes dispatched in current slice */
+ uint64_t bytes_disp[2];
+ /* Number of bio's dispatched in current slice */
+ unsigned int io_disp[2];
+
+ unsigned long last_low_overflow_time[2];
+
+ uint64_t last_bytes_disp[2];
+ unsigned int last_io_disp[2];
+
+ unsigned long last_check_time;
+
+ unsigned long latency_target; /* us */
+ unsigned long latency_target_conf; /* us */
+ /* When did we start a new slice */
+ unsigned long slice_start[2];
+ unsigned long slice_end[2];
+
+ unsigned long last_finish_time; /* ns / 1024 */
+ unsigned long checked_last_finish_time; /* ns / 1024 */
+ unsigned long avg_idletime; /* ns / 1024 */
+ unsigned long idletime_threshold; /* us */
+ unsigned long idletime_threshold_conf; /* us */
+
+ unsigned int bio_cnt; /* total bios */
+ unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
+ unsigned long bio_cnt_reset_time;
+
+ atomic_t io_split_cnt[2];
+ atomic_t last_io_split_cnt[2];
+
+ struct blkg_rwstat stat_bytes;
+ struct blkg_rwstat stat_ios;
+};
+
+extern struct blkcg_policy blkcg_policy_throtl;
+
+static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
+{
+ return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
+}
+
+static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
+{
+ return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
+}
+
+/*
+ * Internal throttling interface
+ */
+#ifndef CONFIG_BLK_DEV_THROTTLING
+static inline int blk_throtl_init(struct request_queue *q) { return 0; }
+static inline void blk_throtl_exit(struct request_queue *q) { }
+static inline void blk_throtl_register_queue(struct request_queue *q) { }
+static inline void blk_throtl_charge_bio_split(struct bio *bio) { }
+static inline bool blk_throtl_bio(struct bio *bio) { return false; }
+#else /* CONFIG_BLK_DEV_THROTTLING */
+int blk_throtl_init(struct request_queue *q);
+void blk_throtl_exit(struct request_queue *q);
+void blk_throtl_register_queue(struct request_queue *q);
+void blk_throtl_charge_bio_split(struct bio *bio);
+bool __blk_throtl_bio(struct bio *bio);
+static inline bool blk_throtl_bio(struct bio *bio)
+{
+ struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
+
+ if (bio_flagged(bio, BIO_THROTTLED))
+ return false;
+ if (!tg->has_rules[bio_data_dir(bio)])
+ return false;
+
+ return __blk_throtl_bio(bio);
+}
+#endif /* CONFIG_BLK_DEV_THROTTLING */
+
+#endif