File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
new file mode 100644
index 0000000..2149a1d
--- /dev/null
+++ b/block/blk-throttle.c
@@ -0,0 +1,1594 @@
+/*
+ * Interface for controlling IO bandwidth on a request queue
+ *
+ * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/blktrace_api.h>
+#include <linux/blk-cgroup.h>
+#include "blk.h"
+
+/* Max dispatch from a group in 1 round */
+static int throtl_grp_quantum = 8;
+
+/* Total max dispatch from all groups in one round */
+static int throtl_quantum = 32;
+
+/* Throttling is performed over 100ms slice and after that slice is renewed */
+static unsigned long throtl_slice = HZ/10; /* 100 ms */
+
+static struct blkcg_policy blkcg_policy_throtl;
+
+/* A workqueue to queue throttle related work */
+static struct workqueue_struct *kthrotld_workqueue;
+
+/*
+ * 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 pending_tree; /* RB tree of active tgs */
+ struct rb_node *first_pending; /* first node in the tree */
+ 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 */
+};
+
+#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
+
+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];
+
+ /* bytes per second rate limits */
+ uint64_t bps[2];
+
+ /* IOPS limits */
+ unsigned int iops[2];
+
+ /* Number of bytes disptached in current slice */
+ uint64_t bytes_disp[2];
+ /* Number of bio's dispatched in current slice */
+ unsigned int io_disp[2];
+
+ /* When did we start a new slice */
+ unsigned long slice_start[2];
+ unsigned long slice_end[2];
+};
+
+struct throtl_data
+{
+ /* service tree for active throtl groups */
+ struct throtl_service_queue service_queue;
+
+ struct request_queue *queue;
+
+ /* Total Number of queued bios on READ and WRITE lists */
+ unsigned int nr_queued[2];
+
+ /*
+ * number of total undestroyed groups
+ */
+ unsigned int nr_undestroyed_grps;
+
+ /* Work for dispatching throttled bios */
+ struct work_struct dispatch_work;
+};
+
+static void throtl_pending_timer_fn(unsigned long arg);
+
+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));
+}
+
+static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
+{
+ return pd_to_blkg(&tg->pd);
+}
+
+/**
+ * sq_to_tg - return the throl_grp the specified service queue belongs to
+ * @sq: the throtl_service_queue of interest
+ *
+ * Return the throtl_grp @sq belongs to. If @sq is the top-level one
+ * embedded in throtl_data, %NULL is returned.
+ */
+static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
+{
+ if (sq && sq->parent_sq)
+ return container_of(sq, struct throtl_grp, service_queue);
+ else
+ return NULL;
+}
+
+/**
+ * sq_to_td - return throtl_data the specified service queue belongs to
+ * @sq: the throtl_service_queue of interest
+ *
+ * A service_queue can be embeded in either a throtl_grp or throtl_data.
+ * Determine the associated throtl_data accordingly and return it.
+ */
+static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
+{
+ struct throtl_grp *tg = sq_to_tg(sq);
+
+ if (tg)
+ return tg->td;
+ else
+ return container_of(sq, struct throtl_data, service_queue);
+}
+
+/**
+ * throtl_log - log debug message via blktrace
+ * @sq: the service_queue being reported
+ * @fmt: printf format string
+ * @args: printf args
+ *
+ * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
+ * throtl_grp; otherwise, just "throtl".
+ *
+ * TODO: this should be made a function and name formatting should happen
+ * after testing whether blktrace is enabled.
+ */
+#define throtl_log(sq, fmt, args...) do { \
+ struct throtl_grp *__tg = sq_to_tg((sq)); \
+ struct throtl_data *__td = sq_to_td((sq)); \
+ \
+ (void)__td; \
+ if ((__tg)) { \
+ char __pbuf[128]; \
+ \
+ blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
+ blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
+ } else { \
+ blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
+ } \
+} while (0)
+
+static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
+{
+ INIT_LIST_HEAD(&qn->node);
+ bio_list_init(&qn->bios);
+ qn->tg = tg;
+}
+
+/**
+ * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
+ * @bio: bio being added
+ * @qn: qnode to add bio to
+ * @queued: the service_queue->queued[] list @qn belongs to
+ *
+ * Add @bio to @qn and put @qn on @queued if it's not already on.
+ * @qn->tg's reference count is bumped when @qn is activated. See the
+ * comment on top of throtl_qnode definition for details.
+ */
+static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
+ struct list_head *queued)
+{
+ bio_list_add(&qn->bios, bio);
+ if (list_empty(&qn->node)) {
+ list_add_tail(&qn->node, queued);
+ blkg_get(tg_to_blkg(qn->tg));
+ }
+}
+
+/**
+ * throtl_peek_queued - peek the first bio on a qnode list
+ * @queued: the qnode list to peek
+ */
+static struct bio *throtl_peek_queued(struct list_head *queued)
+{
+ struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
+ struct bio *bio;
+
+ if (list_empty(queued))
+ return NULL;
+
+ bio = bio_list_peek(&qn->bios);
+ WARN_ON_ONCE(!bio);
+ return bio;
+}
+
+/**
+ * throtl_pop_queued - pop the first bio form a qnode list
+ * @queued: the qnode list to pop a bio from
+ * @tg_to_put: optional out argument for throtl_grp to put
+ *
+ * Pop the first bio from the qnode list @queued. After popping, the first
+ * qnode is removed from @queued if empty or moved to the end of @queued so
+ * that the popping order is round-robin.
+ *
+ * When the first qnode is removed, its associated throtl_grp should be put
+ * too. If @tg_to_put is NULL, this function automatically puts it;
+ * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
+ * responsible for putting it.
+ */
+static struct bio *throtl_pop_queued(struct list_head *queued,
+ struct throtl_grp **tg_to_put)
+{
+ struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
+ struct bio *bio;
+
+ if (list_empty(queued))
+ return NULL;
+
+ bio = bio_list_pop(&qn->bios);
+ WARN_ON_ONCE(!bio);
+
+ if (bio_list_empty(&qn->bios)) {
+ list_del_init(&qn->node);
+ if (tg_to_put)
+ *tg_to_put = qn->tg;
+ else
+ blkg_put(tg_to_blkg(qn->tg));
+ } else {
+ list_move_tail(&qn->node, queued);
+ }
+
+ return bio;
+}
+
+/* init a service_queue, assumes the caller zeroed it */
+static void throtl_service_queue_init(struct throtl_service_queue *sq)
+{
+ INIT_LIST_HEAD(&sq->queued[0]);
+ INIT_LIST_HEAD(&sq->queued[1]);
+ sq->pending_tree = RB_ROOT;
+ setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
+ (unsigned long)sq);
+}
+
+static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
+{
+ struct throtl_grp *tg;
+ int rw;
+
+ tg = kzalloc_node(sizeof(*tg), gfp, node);
+ if (!tg)
+ return NULL;
+
+ throtl_service_queue_init(&tg->service_queue);
+
+ for (rw = READ; rw <= WRITE; rw++) {
+ throtl_qnode_init(&tg->qnode_on_self[rw], tg);
+ throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
+ }
+
+ RB_CLEAR_NODE(&tg->rb_node);
+ tg->bps[READ] = -1;
+ tg->bps[WRITE] = -1;
+ tg->iops[READ] = -1;
+ tg->iops[WRITE] = -1;
+
+ return &tg->pd;
+}
+
+static void throtl_pd_init(struct blkg_policy_data *pd)
+{
+ struct throtl_grp *tg = pd_to_tg(pd);
+ struct blkcg_gq *blkg = tg_to_blkg(tg);
+ struct throtl_data *td = blkg->q->td;
+ struct throtl_service_queue *sq = &tg->service_queue;
+
+ /*
+ * If on the default hierarchy, we switch to properly hierarchical
+ * behavior where limits on a given throtl_grp are applied to the
+ * whole subtree rather than just the group itself. e.g. If 16M
+ * read_bps limit is set on the root group, the whole system can't
+ * exceed 16M for the device.
+ *
+ * If not on the default hierarchy, the broken flat hierarchy
+ * behavior is retained where all throtl_grps are treated as if
+ * they're all separate root groups right below throtl_data.
+ * Limits of a group don't interact with limits of other groups
+ * regardless of the position of the group in the hierarchy.
+ */
+ sq->parent_sq = &td->service_queue;
+ if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
+ sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
+ tg->td = td;
+}
+
+/*
+ * Set has_rules[] if @tg or any of its parents have limits configured.
+ * This doesn't require walking up to the top of the hierarchy as the
+ * parent's has_rules[] is guaranteed to be correct.
+ */
+static void tg_update_has_rules(struct throtl_grp *tg)
+{
+ struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
+ int rw;
+
+ for (rw = READ; rw <= WRITE; rw++)
+ tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
+ (tg->bps[rw] != -1 || tg->iops[rw] != -1);
+}
+
+static void throtl_pd_online(struct blkg_policy_data *pd)
+{
+ /*
+ * We don't want new groups to escape the limits of its ancestors.
+ * Update has_rules[] after a new group is brought online.
+ */
+ tg_update_has_rules(pd_to_tg(pd));
+}
+
+static void throtl_pd_free(struct blkg_policy_data *pd)
+{
+ struct throtl_grp *tg = pd_to_tg(pd);
+
+ del_timer_sync(&tg->service_queue.pending_timer);
+ kfree(tg);
+}
+
+static struct throtl_grp *
+throtl_rb_first(struct throtl_service_queue *parent_sq)
+{
+ /* Service tree is empty */
+ if (!parent_sq->nr_pending)
+ return NULL;
+
+ if (!parent_sq->first_pending)
+ parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
+
+ if (parent_sq->first_pending)
+ return rb_entry_tg(parent_sq->first_pending);
+
+ return NULL;
+}
+
+static void rb_erase_init(struct rb_node *n, struct rb_root *root)
+{
+ rb_erase(n, root);
+ RB_CLEAR_NODE(n);
+}
+
+static void throtl_rb_erase(struct rb_node *n,
+ struct throtl_service_queue *parent_sq)
+{
+ if (parent_sq->first_pending == n)
+ parent_sq->first_pending = NULL;
+ rb_erase_init(n, &parent_sq->pending_tree);
+ --parent_sq->nr_pending;
+}
+
+static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
+{
+ struct throtl_grp *tg;
+
+ tg = throtl_rb_first(parent_sq);
+ if (!tg)
+ return;
+
+ parent_sq->first_pending_disptime = tg->disptime;
+}
+
+static void tg_service_queue_add(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
+ struct rb_node **node = &parent_sq->pending_tree.rb_node;
+ struct rb_node *parent = NULL;
+ struct throtl_grp *__tg;
+ unsigned long key = tg->disptime;
+ int left = 1;
+
+ while (*node != NULL) {
+ parent = *node;
+ __tg = rb_entry_tg(parent);
+
+ if (time_before(key, __tg->disptime))
+ node = &parent->rb_left;
+ else {
+ node = &parent->rb_right;
+ left = 0;
+ }
+ }
+
+ if (left)
+ parent_sq->first_pending = &tg->rb_node;
+
+ rb_link_node(&tg->rb_node, parent, node);
+ rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
+}
+
+static void __throtl_enqueue_tg(struct throtl_grp *tg)
+{
+ tg_service_queue_add(tg);
+ tg->flags |= THROTL_TG_PENDING;
+ tg->service_queue.parent_sq->nr_pending++;
+}
+
+static void throtl_enqueue_tg(struct throtl_grp *tg)
+{
+ if (!(tg->flags & THROTL_TG_PENDING))
+ __throtl_enqueue_tg(tg);
+}
+
+static void __throtl_dequeue_tg(struct throtl_grp *tg)
+{
+ throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
+ tg->flags &= ~THROTL_TG_PENDING;
+}
+
+static void throtl_dequeue_tg(struct throtl_grp *tg)
+{
+ if (tg->flags & THROTL_TG_PENDING)
+ __throtl_dequeue_tg(tg);
+}
+
+/* Call with queue lock held */
+static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
+ unsigned long expires)
+{
+ mod_timer(&sq->pending_timer, expires);
+ throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
+ expires - jiffies, jiffies);
+}
+
+/**
+ * throtl_schedule_next_dispatch - schedule the next dispatch cycle
+ * @sq: the service_queue to schedule dispatch for
+ * @force: force scheduling
+ *
+ * Arm @sq->pending_timer so that the next dispatch cycle starts on the
+ * dispatch time of the first pending child. Returns %true if either timer
+ * is armed or there's no pending child left. %false if the current
+ * dispatch window is still open and the caller should continue
+ * dispatching.
+ *
+ * If @force is %true, the dispatch timer is always scheduled and this
+ * function is guaranteed to return %true. This is to be used when the
+ * caller can't dispatch itself and needs to invoke pending_timer
+ * unconditionally. Note that forced scheduling is likely to induce short
+ * delay before dispatch starts even if @sq->first_pending_disptime is not
+ * in the future and thus shouldn't be used in hot paths.
+ */
+static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
+ bool force)
+{
+ /* any pending children left? */
+ if (!sq->nr_pending)
+ return true;
+
+ update_min_dispatch_time(sq);
+
+ /* is the next dispatch time in the future? */
+ if (force || time_after(sq->first_pending_disptime, jiffies)) {
+ throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
+ return true;
+ }
+
+ /* tell the caller to continue dispatching */
+ return false;
+}
+
+static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
+ bool rw, unsigned long start)
+{
+ tg->bytes_disp[rw] = 0;
+ tg->io_disp[rw] = 0;
+
+ /*
+ * Previous slice has expired. We must have trimmed it after last
+ * bio dispatch. That means since start of last slice, we never used
+ * that bandwidth. Do try to make use of that bandwidth while giving
+ * credit.
+ */
+ if (time_after_eq(start, tg->slice_start[rw]))
+ tg->slice_start[rw] = start;
+
+ tg->slice_end[rw] = jiffies + throtl_slice;
+ throtl_log(&tg->service_queue,
+ "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
+ rw == READ ? 'R' : 'W', tg->slice_start[rw],
+ tg->slice_end[rw], jiffies);
+}
+
+static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
+{
+ tg->bytes_disp[rw] = 0;
+ tg->io_disp[rw] = 0;
+ tg->slice_start[rw] = jiffies;
+ tg->slice_end[rw] = jiffies + throtl_slice;
+ throtl_log(&tg->service_queue,
+ "[%c] new slice start=%lu end=%lu jiffies=%lu",
+ rw == READ ? 'R' : 'W', tg->slice_start[rw],
+ tg->slice_end[rw], jiffies);
+}
+
+static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
+ unsigned long jiffy_end)
+{
+ tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
+}
+
+static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
+ unsigned long jiffy_end)
+{
+ tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
+ throtl_log(&tg->service_queue,
+ "[%c] extend slice start=%lu end=%lu jiffies=%lu",
+ rw == READ ? 'R' : 'W', tg->slice_start[rw],
+ tg->slice_end[rw], jiffies);
+}
+
+/* Determine if previously allocated or extended slice is complete or not */
+static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
+{
+ if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
+ return false;
+
+ return 1;
+}
+
+/* Trim the used slices and adjust slice start accordingly */
+static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
+{
+ unsigned long nr_slices, time_elapsed, io_trim;
+ u64 bytes_trim, tmp;
+
+ BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
+
+ /*
+ * If bps are unlimited (-1), then time slice don't get
+ * renewed. Don't try to trim the slice if slice is used. A new
+ * slice will start when appropriate.
+ */
+ if (throtl_slice_used(tg, rw))
+ return;
+
+ /*
+ * A bio has been dispatched. Also adjust slice_end. It might happen
+ * that initially cgroup limit was very low resulting in high
+ * slice_end, but later limit was bumped up and bio was dispached
+ * sooner, then we need to reduce slice_end. A high bogus slice_end
+ * is bad because it does not allow new slice to start.
+ */
+
+ throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
+
+ time_elapsed = jiffies - tg->slice_start[rw];
+
+ nr_slices = time_elapsed / throtl_slice;
+
+ if (!nr_slices)
+ return;
+ tmp = tg->bps[rw] * throtl_slice * nr_slices;
+ do_div(tmp, HZ);
+ bytes_trim = tmp;
+
+ io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
+
+ if (!bytes_trim && !io_trim)
+ return;
+
+ if (tg->bytes_disp[rw] >= bytes_trim)
+ tg->bytes_disp[rw] -= bytes_trim;
+ else
+ tg->bytes_disp[rw] = 0;
+
+ if (tg->io_disp[rw] >= io_trim)
+ tg->io_disp[rw] -= io_trim;
+ else
+ tg->io_disp[rw] = 0;
+
+ tg->slice_start[rw] += nr_slices * throtl_slice;
+
+ throtl_log(&tg->service_queue,
+ "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
+ rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
+ tg->slice_start[rw], tg->slice_end[rw], jiffies);
+}
+
+static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
+ unsigned long *wait)
+{
+ bool rw = bio_data_dir(bio);
+ unsigned int io_allowed;
+ unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
+ u64 tmp;
+
+ jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
+
+ /* Slice has just started. Consider one slice interval */
+ if (!jiffy_elapsed)
+ jiffy_elapsed_rnd = throtl_slice;
+
+ jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
+
+ /*
+ * jiffy_elapsed_rnd should not be a big value as minimum iops can be
+ * 1 then at max jiffy elapsed should be equivalent of 1 second as we
+ * will allow dispatch after 1 second and after that slice should
+ * have been trimmed.
+ */
+
+ tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
+ do_div(tmp, HZ);
+
+ if (tmp > UINT_MAX)
+ io_allowed = UINT_MAX;
+ else
+ io_allowed = tmp;
+
+ if (tg->io_disp[rw] + 1 <= io_allowed) {
+ if (wait)
+ *wait = 0;
+ return true;
+ }
+
+ /* Calc approx time to dispatch */
+ jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
+
+ if (jiffy_wait > jiffy_elapsed)
+ jiffy_wait = jiffy_wait - jiffy_elapsed;
+ else
+ jiffy_wait = 1;
+
+ if (wait)
+ *wait = jiffy_wait;
+ return 0;
+}
+
+static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
+ unsigned long *wait)
+{
+ bool rw = bio_data_dir(bio);
+ u64 bytes_allowed, extra_bytes, tmp;
+ unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
+
+ jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
+
+ /* Slice has just started. Consider one slice interval */
+ if (!jiffy_elapsed)
+ jiffy_elapsed_rnd = throtl_slice;
+
+ jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
+
+ tmp = tg->bps[rw] * jiffy_elapsed_rnd;
+ do_div(tmp, HZ);
+ bytes_allowed = tmp;
+
+ if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
+ if (wait)
+ *wait = 0;
+ return true;
+ }
+
+ /* Calc approx time to dispatch */
+ extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
+ jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
+
+ if (!jiffy_wait)
+ jiffy_wait = 1;
+
+ /*
+ * This wait time is without taking into consideration the rounding
+ * up we did. Add that time also.
+ */
+ jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
+ if (wait)
+ *wait = jiffy_wait;
+ return 0;
+}
+
+/*
+ * Returns whether one can dispatch a bio or not. Also returns approx number
+ * of jiffies to wait before this bio is with-in IO rate and can be dispatched
+ */
+static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
+ unsigned long *wait)
+{
+ bool rw = bio_data_dir(bio);
+ unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
+
+ /*
+ * Currently whole state machine of group depends on first bio
+ * queued in the group bio list. So one should not be calling
+ * this function with a different bio if there are other bios
+ * queued.
+ */
+ BUG_ON(tg->service_queue.nr_queued[rw] &&
+ bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
+
+ /* If tg->bps = -1, then BW is unlimited */
+ if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
+ if (wait)
+ *wait = 0;
+ return true;
+ }
+
+ /*
+ * If previous slice expired, start a new one otherwise renew/extend
+ * existing slice to make sure it is at least throtl_slice interval
+ * long since now.
+ */
+ if (throtl_slice_used(tg, rw))
+ throtl_start_new_slice(tg, rw);
+ else {
+ if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
+ throtl_extend_slice(tg, rw, jiffies + throtl_slice);
+ }
+
+ if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
+ tg_with_in_iops_limit(tg, bio, &iops_wait)) {
+ if (wait)
+ *wait = 0;
+ return 1;
+ }
+
+ max_wait = max(bps_wait, iops_wait);
+
+ if (wait)
+ *wait = max_wait;
+
+ if (time_before(tg->slice_end[rw], jiffies + max_wait))
+ throtl_extend_slice(tg, rw, jiffies + max_wait);
+
+ return 0;
+}
+
+static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
+{
+ bool rw = bio_data_dir(bio);
+
+ /* Charge the bio to the group */
+ tg->bytes_disp[rw] += bio->bi_iter.bi_size;
+ tg->io_disp[rw]++;
+
+ /*
+ * REQ_THROTTLED is used to prevent the same bio to be throttled
+ * more than once as a throttled bio will go through blk-throtl the
+ * second time when it eventually gets issued. Set it when a bio
+ * is being charged to a tg.
+ */
+ if (!(bio->bi_rw & REQ_THROTTLED))
+ bio->bi_rw |= REQ_THROTTLED;
+}
+
+/**
+ * throtl_add_bio_tg - add a bio to the specified throtl_grp
+ * @bio: bio to add
+ * @qn: qnode to use
+ * @tg: the target throtl_grp
+ *
+ * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
+ * tg->qnode_on_self[] is used.
+ */
+static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
+ struct throtl_grp *tg)
+{
+ struct throtl_service_queue *sq = &tg->service_queue;
+ bool rw = bio_data_dir(bio);
+
+ if (!qn)
+ qn = &tg->qnode_on_self[rw];
+
+ /*
+ * If @tg doesn't currently have any bios queued in the same
+ * direction, queueing @bio can change when @tg should be
+ * dispatched. Mark that @tg was empty. This is automatically
+ * cleaered on the next tg_update_disptime().
+ */
+ if (!sq->nr_queued[rw])
+ tg->flags |= THROTL_TG_WAS_EMPTY;
+
+ throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
+
+ sq->nr_queued[rw]++;
+ throtl_enqueue_tg(tg);
+}
+
+static void tg_update_disptime(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *sq = &tg->service_queue;
+ unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
+ struct bio *bio;
+
+ if ((bio = throtl_peek_queued(&sq->queued[READ])))
+ tg_may_dispatch(tg, bio, &read_wait);
+
+ if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
+ tg_may_dispatch(tg, bio, &write_wait);
+
+ min_wait = min(read_wait, write_wait);
+ disptime = jiffies + min_wait;
+
+ /* Update dispatch time */
+ throtl_dequeue_tg(tg);
+ tg->disptime = disptime;
+ throtl_enqueue_tg(tg);
+
+ /* see throtl_add_bio_tg() */
+ tg->flags &= ~THROTL_TG_WAS_EMPTY;
+}
+
+static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
+ struct throtl_grp *parent_tg, bool rw)
+{
+ if (throtl_slice_used(parent_tg, rw)) {
+ throtl_start_new_slice_with_credit(parent_tg, rw,
+ child_tg->slice_start[rw]);
+ }
+
+}
+
+static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
+{
+ struct throtl_service_queue *sq = &tg->service_queue;
+ struct throtl_service_queue *parent_sq = sq->parent_sq;
+ struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
+ struct throtl_grp *tg_to_put = NULL;
+ struct bio *bio;
+
+ /*
+ * @bio is being transferred from @tg to @parent_sq. Popping a bio
+ * from @tg may put its reference and @parent_sq might end up
+ * getting released prematurely. Remember the tg to put and put it
+ * after @bio is transferred to @parent_sq.
+ */
+ bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
+ sq->nr_queued[rw]--;
+
+ throtl_charge_bio(tg, bio);
+
+ /*
+ * If our parent is another tg, we just need to transfer @bio to
+ * the parent using throtl_add_bio_tg(). If our parent is
+ * @td->service_queue, @bio is ready to be issued. Put it on its
+ * bio_lists[] and decrease total number queued. The caller is
+ * responsible for issuing these bios.
+ */
+ if (parent_tg) {
+ throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
+ start_parent_slice_with_credit(tg, parent_tg, rw);
+ } else {
+ throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
+ &parent_sq->queued[rw]);
+ BUG_ON(tg->td->nr_queued[rw] <= 0);
+ tg->td->nr_queued[rw]--;
+ }
+
+ throtl_trim_slice(tg, rw);
+
+ if (tg_to_put)
+ blkg_put(tg_to_blkg(tg_to_put));
+}
+
+static int throtl_dispatch_tg(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *sq = &tg->service_queue;
+ unsigned int nr_reads = 0, nr_writes = 0;
+ unsigned int max_nr_reads = throtl_grp_quantum*3/4;
+ unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
+ struct bio *bio;
+
+ /* Try to dispatch 75% READS and 25% WRITES */
+
+ while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
+ tg_may_dispatch(tg, bio, NULL)) {
+
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ nr_reads++;
+
+ if (nr_reads >= max_nr_reads)
+ break;
+ }
+
+ while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
+ tg_may_dispatch(tg, bio, NULL)) {
+
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ nr_writes++;
+
+ if (nr_writes >= max_nr_writes)
+ break;
+ }
+
+ return nr_reads + nr_writes;
+}
+
+static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
+{
+ unsigned int nr_disp = 0;
+
+ while (1) {
+ struct throtl_grp *tg = throtl_rb_first(parent_sq);
+ struct throtl_service_queue *sq = &tg->service_queue;
+
+ if (!tg)
+ break;
+
+ if (time_before(jiffies, tg->disptime))
+ break;
+
+ throtl_dequeue_tg(tg);
+
+ nr_disp += throtl_dispatch_tg(tg);
+
+ if (sq->nr_queued[0] || sq->nr_queued[1])
+ tg_update_disptime(tg);
+
+ if (nr_disp >= throtl_quantum)
+ break;
+ }
+
+ return nr_disp;
+}
+
+/**
+ * throtl_pending_timer_fn - timer function for service_queue->pending_timer
+ * @arg: the throtl_service_queue being serviced
+ *
+ * This timer is armed when a child throtl_grp with active bio's become
+ * pending and queued on the service_queue's pending_tree and expires when
+ * the first child throtl_grp should be dispatched. This function
+ * dispatches bio's from the children throtl_grps to the parent
+ * service_queue.
+ *
+ * If the parent's parent is another throtl_grp, dispatching is propagated
+ * by either arming its pending_timer or repeating dispatch directly. If
+ * the top-level service_tree is reached, throtl_data->dispatch_work is
+ * kicked so that the ready bio's are issued.
+ */
+static void throtl_pending_timer_fn(unsigned long arg)
+{
+ struct throtl_service_queue *sq = (void *)arg;
+ struct throtl_grp *tg = sq_to_tg(sq);
+ struct throtl_data *td = sq_to_td(sq);
+ struct request_queue *q = td->queue;
+ struct throtl_service_queue *parent_sq;
+ bool dispatched;
+ int ret;
+
+ spin_lock_irq(q->queue_lock);
+again:
+ parent_sq = sq->parent_sq;
+ dispatched = false;
+
+ while (true) {
+ throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
+ sq->nr_queued[READ] + sq->nr_queued[WRITE],
+ sq->nr_queued[READ], sq->nr_queued[WRITE]);
+
+ ret = throtl_select_dispatch(sq);
+ if (ret) {
+ throtl_log(sq, "bios disp=%u", ret);
+ dispatched = true;
+ }
+
+ if (throtl_schedule_next_dispatch(sq, false))
+ break;
+
+ /* this dispatch windows is still open, relax and repeat */
+ spin_unlock_irq(q->queue_lock);
+ cpu_relax();
+ spin_lock_irq(q->queue_lock);
+ }
+
+ if (!dispatched)
+ goto out_unlock;
+
+ if (parent_sq) {
+ /* @parent_sq is another throl_grp, propagate dispatch */
+ if (tg->flags & THROTL_TG_WAS_EMPTY) {
+ tg_update_disptime(tg);
+ if (!throtl_schedule_next_dispatch(parent_sq, false)) {
+ /* window is already open, repeat dispatching */
+ sq = parent_sq;
+ tg = sq_to_tg(sq);
+ goto again;
+ }
+ }
+ } else {
+ /* reached the top-level, queue issueing */
+ queue_work(kthrotld_workqueue, &td->dispatch_work);
+ }
+out_unlock:
+ spin_unlock_irq(q->queue_lock);
+}
+
+/**
+ * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
+ * @work: work item being executed
+ *
+ * This function is queued for execution when bio's reach the bio_lists[]
+ * of throtl_data->service_queue. Those bio's are ready and issued by this
+ * function.
+ */
+static void blk_throtl_dispatch_work_fn(struct work_struct *work)
+{
+ struct throtl_data *td = container_of(work, struct throtl_data,
+ dispatch_work);
+ struct throtl_service_queue *td_sq = &td->service_queue;
+ struct request_queue *q = td->queue;
+ struct bio_list bio_list_on_stack;
+ struct bio *bio;
+ struct blk_plug plug;
+ int rw;
+
+ bio_list_init(&bio_list_on_stack);
+
+ spin_lock_irq(q->queue_lock);
+ for (rw = READ; rw <= WRITE; rw++)
+ while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
+ bio_list_add(&bio_list_on_stack, bio);
+ spin_unlock_irq(q->queue_lock);
+
+ if (!bio_list_empty(&bio_list_on_stack)) {
+ blk_start_plug(&plug);
+ while((bio = bio_list_pop(&bio_list_on_stack)))
+ generic_make_request(bio);
+ blk_finish_plug(&plug);
+ }
+}
+
+static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ struct throtl_grp *tg = pd_to_tg(pd);
+ u64 v = *(u64 *)((void *)tg + off);
+
+ if (v == -1)
+ return 0;
+ return __blkg_prfill_u64(sf, pd, v);
+}
+
+static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ struct throtl_grp *tg = pd_to_tg(pd);
+ unsigned int v = *(unsigned int *)((void *)tg + off);
+
+ if (v == -1)
+ return 0;
+ return __blkg_prfill_u64(sf, pd, v);
+}
+
+static int tg_print_conf_u64(struct seq_file *sf, void *v)
+{
+ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
+ &blkcg_policy_throtl, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static int tg_print_conf_uint(struct seq_file *sf, void *v)
+{
+ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
+ &blkcg_policy_throtl, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static void tg_conf_updated(struct throtl_grp *tg)
+{
+ struct throtl_service_queue *sq = &tg->service_queue;
+ struct cgroup_subsys_state *pos_css;
+ struct blkcg_gq *blkg;
+
+ throtl_log(&tg->service_queue,
+ "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
+ tg->bps[READ], tg->bps[WRITE],
+ tg->iops[READ], tg->iops[WRITE]);
+
+ /*
+ * Update has_rules[] flags for the updated tg's subtree. A tg is
+ * considered to have rules if either the tg itself or any of its
+ * ancestors has rules. This identifies groups without any
+ * restrictions in the whole hierarchy and allows them to bypass
+ * blk-throttle.
+ */
+ blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg))
+ tg_update_has_rules(blkg_to_tg(blkg));
+
+ /*
+ * We're already holding queue_lock and know @tg is valid. Let's
+ * apply the new config directly.
+ *
+ * Restart the slices for both READ and WRITES. It might happen
+ * that a group's limit are dropped suddenly and we don't want to
+ * account recently dispatched IO with new low rate.
+ */
+ throtl_start_new_slice(tg, 0);
+ throtl_start_new_slice(tg, 1);
+
+ if (tg->flags & THROTL_TG_PENDING) {
+ tg_update_disptime(tg);
+ throtl_schedule_next_dispatch(sq->parent_sq, true);
+ }
+}
+
+static ssize_t tg_set_conf(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off, bool is_u64)
+{
+ struct blkcg *blkcg = css_to_blkcg(of_css(of));
+ struct blkg_conf_ctx ctx;
+ struct throtl_grp *tg;
+ int ret;
+ u64 v;
+
+ ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
+ if (ret)
+ return ret;
+
+ ret = -EINVAL;
+ if (sscanf(ctx.body, "%llu", &v) != 1)
+ goto out_finish;
+ if (!v)
+ v = -1;
+
+ tg = blkg_to_tg(ctx.blkg);
+
+ if (is_u64)
+ *(u64 *)((void *)tg + of_cft(of)->private) = v;
+ else
+ *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
+
+ tg_conf_updated(tg);
+ ret = 0;
+out_finish:
+ blkg_conf_finish(&ctx);
+ return ret ?: nbytes;
+}
+
+static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ return tg_set_conf(of, buf, nbytes, off, true);
+}
+
+static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ return tg_set_conf(of, buf, nbytes, off, false);
+}
+
+static struct cftype throtl_legacy_files[] = {
+ {
+ .name = "throttle.read_bps_device",
+ .private = offsetof(struct throtl_grp, bps[READ]),
+ .seq_show = tg_print_conf_u64,
+ .write = tg_set_conf_u64,
+ },
+ {
+ .name = "throttle.write_bps_device",
+ .private = offsetof(struct throtl_grp, bps[WRITE]),
+ .seq_show = tg_print_conf_u64,
+ .write = tg_set_conf_u64,
+ },
+ {
+ .name = "throttle.read_iops_device",
+ .private = offsetof(struct throtl_grp, iops[READ]),
+ .seq_show = tg_print_conf_uint,
+ .write = tg_set_conf_uint,
+ },
+ {
+ .name = "throttle.write_iops_device",
+ .private = offsetof(struct throtl_grp, iops[WRITE]),
+ .seq_show = tg_print_conf_uint,
+ .write = tg_set_conf_uint,
+ },
+ {
+ .name = "throttle.io_service_bytes",
+ .private = (unsigned long)&blkcg_policy_throtl,
+ .seq_show = blkg_print_stat_bytes,
+ },
+ {
+ .name = "throttle.io_serviced",
+ .private = (unsigned long)&blkcg_policy_throtl,
+ .seq_show = blkg_print_stat_ios,
+ },
+ { } /* terminate */
+};
+
+static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ struct throtl_grp *tg = pd_to_tg(pd);
+ const char *dname = blkg_dev_name(pd->blkg);
+ char bufs[4][21] = { "max", "max", "max", "max" };
+
+ if (!dname)
+ return 0;
+ if (tg->bps[READ] == -1 && tg->bps[WRITE] == -1 &&
+ tg->iops[READ] == -1 && tg->iops[WRITE] == -1)
+ return 0;
+
+ if (tg->bps[READ] != -1)
+ snprintf(bufs[0], sizeof(bufs[0]), "%llu", tg->bps[READ]);
+ if (tg->bps[WRITE] != -1)
+ snprintf(bufs[1], sizeof(bufs[1]), "%llu", tg->bps[WRITE]);
+ if (tg->iops[READ] != -1)
+ snprintf(bufs[2], sizeof(bufs[2]), "%u", tg->iops[READ]);
+ if (tg->iops[WRITE] != -1)
+ snprintf(bufs[3], sizeof(bufs[3]), "%u", tg->iops[WRITE]);
+
+ seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
+ dname, bufs[0], bufs[1], bufs[2], bufs[3]);
+ return 0;
+}
+
+static int tg_print_max(struct seq_file *sf, void *v)
+{
+ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_max,
+ &blkcg_policy_throtl, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static ssize_t tg_set_max(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct blkcg *blkcg = css_to_blkcg(of_css(of));
+ struct blkg_conf_ctx ctx;
+ struct throtl_grp *tg;
+ u64 v[4];
+ int ret;
+
+ ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
+ if (ret)
+ return ret;
+
+ tg = blkg_to_tg(ctx.blkg);
+
+ v[0] = tg->bps[READ];
+ v[1] = tg->bps[WRITE];
+ v[2] = tg->iops[READ];
+ v[3] = tg->iops[WRITE];
+
+ while (true) {
+ char tok[27]; /* wiops=18446744073709551616 */
+ char *p;
+ u64 val = -1;
+ int len;
+
+ if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
+ break;
+ if (tok[0] == '\0')
+ break;
+ ctx.body += len;
+
+ ret = -EINVAL;
+ p = tok;
+ strsep(&p, "=");
+ if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
+ goto out_finish;
+
+ ret = -ERANGE;
+ if (!val)
+ goto out_finish;
+
+ ret = -EINVAL;
+ if (!strcmp(tok, "rbps"))
+ v[0] = val;
+ else if (!strcmp(tok, "wbps"))
+ v[1] = val;
+ else if (!strcmp(tok, "riops"))
+ v[2] = min_t(u64, val, UINT_MAX);
+ else if (!strcmp(tok, "wiops"))
+ v[3] = min_t(u64, val, UINT_MAX);
+ else
+ goto out_finish;
+ }
+
+ tg->bps[READ] = v[0];
+ tg->bps[WRITE] = v[1];
+ tg->iops[READ] = v[2];
+ tg->iops[WRITE] = v[3];
+
+ tg_conf_updated(tg);
+ ret = 0;
+out_finish:
+ blkg_conf_finish(&ctx);
+ return ret ?: nbytes;
+}
+
+static struct cftype throtl_files[] = {
+ {
+ .name = "max",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = tg_print_max,
+ .write = tg_set_max,
+ },
+ { } /* terminate */
+};
+
+static void throtl_shutdown_wq(struct request_queue *q)
+{
+ struct throtl_data *td = q->td;
+
+ cancel_work_sync(&td->dispatch_work);
+}
+
+static struct blkcg_policy blkcg_policy_throtl = {
+ .dfl_cftypes = throtl_files,
+ .legacy_cftypes = throtl_legacy_files,
+
+ .pd_alloc_fn = throtl_pd_alloc,
+ .pd_init_fn = throtl_pd_init,
+ .pd_online_fn = throtl_pd_online,
+ .pd_free_fn = throtl_pd_free,
+};
+
+bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
+ struct bio *bio)
+{
+ struct throtl_qnode *qn = NULL;
+ struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
+ struct throtl_service_queue *sq;
+ bool rw = bio_data_dir(bio);
+ bool throttled = false;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ /* see throtl_charge_bio() */
+ if ((bio->bi_rw & REQ_THROTTLED) || !tg->has_rules[rw])
+ goto out;
+
+ spin_lock_irq(q->queue_lock);
+
+ if (unlikely(blk_queue_bypass(q)))
+ goto out_unlock;
+
+ sq = &tg->service_queue;
+
+ while (true) {
+ /* throtl is FIFO - if bios are already queued, should queue */
+ if (sq->nr_queued[rw])
+ break;
+
+ /* if above limits, break to queue */
+ if (!tg_may_dispatch(tg, bio, NULL))
+ break;
+
+ /* within limits, let's charge and dispatch directly */
+ throtl_charge_bio(tg, bio);
+
+ /*
+ * We need to trim slice even when bios are not being queued
+ * otherwise it might happen that a bio is not queued for
+ * a long time and slice keeps on extending and trim is not
+ * called for a long time. Now if limits are reduced suddenly
+ * we take into account all the IO dispatched so far at new
+ * low rate and * newly queued IO gets a really long dispatch
+ * time.
+ *
+ * So keep on trimming slice even if bio is not queued.
+ */
+ throtl_trim_slice(tg, rw);
+
+ /*
+ * @bio passed through this layer without being throttled.
+ * Climb up the ladder. If we''re already at the top, it
+ * can be executed directly.
+ */
+ qn = &tg->qnode_on_parent[rw];
+ sq = sq->parent_sq;
+ tg = sq_to_tg(sq);
+ if (!tg)
+ goto out_unlock;
+ }
+
+ /* out-of-limit, queue to @tg */
+ throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
+ rw == READ ? 'R' : 'W',
+ tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
+ tg->io_disp[rw], tg->iops[rw],
+ sq->nr_queued[READ], sq->nr_queued[WRITE]);
+
+ bio_associate_current(bio);
+ tg->td->nr_queued[rw]++;
+ throtl_add_bio_tg(bio, qn, tg);
+ throttled = true;
+
+ /*
+ * Update @tg's dispatch time and force schedule dispatch if @tg
+ * was empty before @bio. The forced scheduling isn't likely to
+ * cause undue delay as @bio is likely to be dispatched directly if
+ * its @tg's disptime is not in the future.
+ */
+ if (tg->flags & THROTL_TG_WAS_EMPTY) {
+ tg_update_disptime(tg);
+ throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
+ }
+
+out_unlock:
+ spin_unlock_irq(q->queue_lock);
+out:
+ /*
+ * As multiple blk-throtls may stack in the same issue path, we
+ * don't want bios to leave with the flag set. Clear the flag if
+ * being issued.
+ */
+ if (!throttled)
+ bio->bi_rw &= ~REQ_THROTTLED;
+ return throttled;
+}
+
+/*
+ * Dispatch all bios from all children tg's queued on @parent_sq. On
+ * return, @parent_sq is guaranteed to not have any active children tg's
+ * and all bios from previously active tg's are on @parent_sq->bio_lists[].
+ */
+static void tg_drain_bios(struct throtl_service_queue *parent_sq)
+{
+ struct throtl_grp *tg;
+
+ while ((tg = throtl_rb_first(parent_sq))) {
+ struct throtl_service_queue *sq = &tg->service_queue;
+ struct bio *bio;
+
+ throtl_dequeue_tg(tg);
+
+ while ((bio = throtl_peek_queued(&sq->queued[READ])))
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ }
+}
+
+/**
+ * blk_throtl_drain - drain throttled bios
+ * @q: request_queue to drain throttled bios for
+ *
+ * Dispatch all currently throttled bios on @q through ->make_request_fn().
+ */
+void blk_throtl_drain(struct request_queue *q)
+ __releases(q->queue_lock) __acquires(q->queue_lock)
+{
+ struct throtl_data *td = q->td;
+ struct blkcg_gq *blkg;
+ struct cgroup_subsys_state *pos_css;
+ struct bio *bio;
+ int rw;
+
+ queue_lockdep_assert_held(q);
+ rcu_read_lock();
+
+ /*
+ * Drain each tg while doing post-order walk on the blkg tree, so
+ * that all bios are propagated to td->service_queue. It'd be
+ * better to walk service_queue tree directly but blkg walk is
+ * easier.
+ */
+ blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
+ tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
+
+ /* finally, transfer bios from top-level tg's into the td */
+ tg_drain_bios(&td->service_queue);
+
+ rcu_read_unlock();
+ spin_unlock_irq(q->queue_lock);
+
+ /* all bios now should be in td->service_queue, issue them */
+ for (rw = READ; rw <= WRITE; rw++)
+ while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
+ NULL)))
+ generic_make_request(bio);
+
+ spin_lock_irq(q->queue_lock);
+}
+
+int blk_throtl_init(struct request_queue *q)
+{
+ struct throtl_data *td;
+ int ret;
+
+ td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
+ if (!td)
+ return -ENOMEM;
+
+ INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
+ throtl_service_queue_init(&td->service_queue);
+
+ q->td = td;
+ td->queue = q;
+
+ /* activate policy */
+ ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
+ if (ret)
+ kfree(td);
+ return ret;
+}
+
+void blk_throtl_exit(struct request_queue *q)
+{
+ BUG_ON(!q->td);
+ throtl_shutdown_wq(q);
+ blkcg_deactivate_policy(q, &blkcg_policy_throtl);
+ kfree(q->td);
+}
+
+static int __init throtl_init(void)
+{
+ kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
+ if (!kthrotld_workqueue)
+ panic("Failed to create kthrotld\n");
+
+ return blkcg_policy_register(&blkcg_policy_throtl);
+}
+
+module_init(throtl_init);