1 files changed, 209 insertions, 0 deletions
diff --git a/block/blk-throttle.h b/block/blk-throttle.h
new file mode 100644
index 000000000000..9d7a42c039a1
--- /dev/null
+++ b/block/blk-throttle.h
@@ -0,0 +1,209 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#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_bps;	/* queued bios for bps limit */
+	struct bio_list		bios_iops;	/* queued bios for iops limit */
+	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_bps[2];	/* number of queued bps bios */
+	unsigned int		nr_queued_iops[2];	/* number of queued iops 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 tg_state_flags {
+	THROTL_TG_PENDING		= 1 << 0,	/* on parent's pending tree */
+	THROTL_TG_WAS_EMPTY		= 1 << 1,	/* bio_lists[] became non-empty */
+	/*
+	 * The sq's iops queue is empty, and a bio is about to be enqueued
+	 * to the first qnode's bios_iops list.
+	 */
+	THROTL_TG_IOPS_WAS_EMPTY	= 1 << 2,
+	THROTL_TG_CANCELING		= 1 << 3,	/* starts to cancel bio */
+};
+
+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_bps[2];
+	bool has_rules_iops[2];
+
+	/* bytes per second rate limits */
+	uint64_t bps[2];
+
+	/* IOPS limits */
+	unsigned int iops[2];
+
+	/*
+	 * Number of bytes/bio's dispatched in current slice.
+	 * When new configuration is submitted while some bios are still throttled,
+	 * first calculate the carryover: the amount of bytes/IOs already waited
+	 * under the previous configuration. Then, [bytes/io]_disp are represented
+	 * as the negative of the carryover, and they will be used to calculate the
+	 * wait time under the new configuration.
+	 */
+	int64_t bytes_disp[2];
+	int io_disp[2];
+
+	unsigned long last_check_time;
+
+	/* When did we start a new slice */
+	unsigned long slice_start[2];
+	unsigned long slice_end[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 void blk_throtl_exit(struct gendisk *disk) { }
+static inline bool blk_throtl_bio(struct bio *bio) { return false; }
+static inline void blk_throtl_cancel_bios(struct gendisk *disk) { }
+#else /* CONFIG_BLK_DEV_THROTTLING */
+void blk_throtl_exit(struct gendisk *disk);
+bool __blk_throtl_bio(struct bio *bio);
+void blk_throtl_cancel_bios(struct gendisk *disk);
+
+static inline bool blk_throtl_activated(struct request_queue *q)
+{
+	/*
+	 * q->td guarantees that the blk-throttle module is already loaded,
+	 * and the plid of blk-throttle is assigned.
+	 * blkcg_policy_enabled() guarantees that the policy is activated
+	 * in the request_queue.
+	 */
+	return q->td != NULL && blkcg_policy_enabled(q, &blkcg_policy_throtl);
+}
+
+static inline bool blk_should_throtl(struct bio *bio)
+{
+	struct throtl_grp *tg;
+	int rw = bio_data_dir(bio);
+
+	if (!blk_throtl_activated(bio->bi_bdev->bd_queue))
+		return false;
+
+	tg = blkg_to_tg(bio->bi_blkg);
+	if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
+		if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
+			bio_set_flag(bio, BIO_CGROUP_ACCT);
+			blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
+					bio->bi_iter.bi_size);
+		}
+		blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
+	}
+
+	/* iops limit is always counted */
+	if (tg->has_rules_iops[rw])
+		return true;
+
+	if (tg->has_rules_bps[rw] && !bio_flagged(bio, BIO_BPS_THROTTLED))
+		return true;
+
+	return false;
+}
+
+static inline bool blk_throtl_bio(struct bio *bio)
+{
+	/*
+	 * block throttling takes effect if the policy is activated
+	 * in the bio's request_queue.
+	 */
+	if (!blk_should_throtl(bio))
+		return false;
+
+	return __blk_throtl_bio(bio);
+}
+#endif /* CONFIG_BLK_DEV_THROTTLING */
+
+#endif