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13369816cb
The blk-iolatency controller measures the time from rq_qos_throttle() to
rq_qos_done_bio() and attributes this time to the first bio that needs
to create the request. This means if a bio is plug-mergeable or
bio-mergeable, it gets to bypass the blk-iolatency controller.
The recent series [1], to tag all bios w/ blkgs undermined how iolatency
was determining which bios it was charging and should process in
rq_qos_done_bio(). Because all bios are being tagged, this caused the
atomic_t for the struct rq_wait inflight count to underflow and result
in a stall.
This patch adds a new flag BIO_TRACKED to let controllers know that a
bio is going through the rq_qos path. blk-iolatency now checks if this
flag is set to see if it should process the bio in rq_qos_done_bio().
Overloading BLK_QUEUE_ENTERED works, but makes the flag rules confusing.
BIO_THROTTLED was another candidate, but the flag is set for all bios
that have gone through blk-throttle code. Overloading a flag comes with
the burden of making sure that when either implementation changes, a
change in setting rules for one doesn't cause a bug in the other. So
here, we unfortunately opt for adding a new flag.
[1] https://lore.kernel.org/lkml/20181205171039.73066-1-dennis@kernel.org/
Fixes: 5cdf2e3fea ("blkcg: associate blkg when associating a device")
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
190 lines
4.4 KiB
C
190 lines
4.4 KiB
C
#ifndef RQ_QOS_H
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#define RQ_QOS_H
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#include <linux/kernel.h>
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#include <linux/blkdev.h>
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#include <linux/blk_types.h>
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#include <linux/atomic.h>
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#include <linux/wait.h>
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#include "blk-mq-debugfs.h"
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struct blk_mq_debugfs_attr;
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enum rq_qos_id {
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RQ_QOS_WBT,
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RQ_QOS_CGROUP,
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};
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struct rq_wait {
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wait_queue_head_t wait;
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atomic_t inflight;
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};
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struct rq_qos {
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struct rq_qos_ops *ops;
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struct request_queue *q;
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enum rq_qos_id id;
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struct rq_qos *next;
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#ifdef CONFIG_BLK_DEBUG_FS
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struct dentry *debugfs_dir;
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#endif
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};
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struct rq_qos_ops {
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void (*throttle)(struct rq_qos *, struct bio *);
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void (*track)(struct rq_qos *, struct request *, struct bio *);
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void (*issue)(struct rq_qos *, struct request *);
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void (*requeue)(struct rq_qos *, struct request *);
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void (*done)(struct rq_qos *, struct request *);
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void (*done_bio)(struct rq_qos *, struct bio *);
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void (*cleanup)(struct rq_qos *, struct bio *);
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void (*exit)(struct rq_qos *);
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const struct blk_mq_debugfs_attr *debugfs_attrs;
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};
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struct rq_depth {
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unsigned int max_depth;
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int scale_step;
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bool scaled_max;
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unsigned int queue_depth;
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unsigned int default_depth;
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};
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static inline struct rq_qos *rq_qos_id(struct request_queue *q,
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enum rq_qos_id id)
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{
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struct rq_qos *rqos;
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for (rqos = q->rq_qos; rqos; rqos = rqos->next) {
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if (rqos->id == id)
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break;
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}
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return rqos;
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}
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static inline struct rq_qos *wbt_rq_qos(struct request_queue *q)
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{
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return rq_qos_id(q, RQ_QOS_WBT);
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}
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static inline struct rq_qos *blkcg_rq_qos(struct request_queue *q)
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{
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return rq_qos_id(q, RQ_QOS_CGROUP);
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}
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static inline const char *rq_qos_id_to_name(enum rq_qos_id id)
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{
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switch (id) {
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case RQ_QOS_WBT:
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return "wbt";
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case RQ_QOS_CGROUP:
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return "cgroup";
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}
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return "unknown";
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}
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static inline void rq_wait_init(struct rq_wait *rq_wait)
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{
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atomic_set(&rq_wait->inflight, 0);
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init_waitqueue_head(&rq_wait->wait);
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}
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static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos)
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{
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rqos->next = q->rq_qos;
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q->rq_qos = rqos;
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if (rqos->ops->debugfs_attrs)
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blk_mq_debugfs_register_rqos(rqos);
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}
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static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
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{
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struct rq_qos *cur, *prev = NULL;
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for (cur = q->rq_qos; cur; cur = cur->next) {
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if (cur == rqos) {
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if (prev)
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prev->next = rqos->next;
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else
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q->rq_qos = cur;
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break;
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}
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prev = cur;
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}
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blk_mq_debugfs_unregister_rqos(rqos);
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}
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typedef bool (acquire_inflight_cb_t)(struct rq_wait *rqw, void *private_data);
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typedef void (cleanup_cb_t)(struct rq_wait *rqw, void *private_data);
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void rq_qos_wait(struct rq_wait *rqw, void *private_data,
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acquire_inflight_cb_t *acquire_inflight_cb,
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cleanup_cb_t *cleanup_cb);
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bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit);
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void rq_depth_scale_up(struct rq_depth *rqd);
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void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle);
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bool rq_depth_calc_max_depth(struct rq_depth *rqd);
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void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio);
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void __rq_qos_done(struct rq_qos *rqos, struct request *rq);
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void __rq_qos_issue(struct rq_qos *rqos, struct request *rq);
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void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq);
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void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio);
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void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio);
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void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio);
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static inline void rq_qos_cleanup(struct request_queue *q, struct bio *bio)
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{
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if (q->rq_qos)
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__rq_qos_cleanup(q->rq_qos, bio);
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}
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static inline void rq_qos_done(struct request_queue *q, struct request *rq)
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{
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if (q->rq_qos)
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__rq_qos_done(q->rq_qos, rq);
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}
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static inline void rq_qos_issue(struct request_queue *q, struct request *rq)
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{
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if (q->rq_qos)
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__rq_qos_issue(q->rq_qos, rq);
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}
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static inline void rq_qos_requeue(struct request_queue *q, struct request *rq)
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{
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if (q->rq_qos)
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__rq_qos_requeue(q->rq_qos, rq);
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}
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static inline void rq_qos_done_bio(struct request_queue *q, struct bio *bio)
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{
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if (q->rq_qos)
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__rq_qos_done_bio(q->rq_qos, bio);
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}
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static inline void rq_qos_throttle(struct request_queue *q, struct bio *bio)
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{
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/*
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* BIO_TRACKED lets controllers know that a bio went through the
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* normal rq_qos path.
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*/
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bio_set_flag(bio, BIO_TRACKED);
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if (q->rq_qos)
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__rq_qos_throttle(q->rq_qos, bio);
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}
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static inline void rq_qos_track(struct request_queue *q, struct request *rq,
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struct bio *bio)
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{
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if (q->rq_qos)
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__rq_qos_track(q->rq_qos, rq, bio);
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}
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void rq_qos_exit(struct request_queue *);
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#endif
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