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SubjectRe: [PATCH 7/8] mq-deadline: add blk-mq adaptation of the deadline IO scheduler
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> Il giorno 20 gen 2017, alle ore 14:14, Paolo Valente <paolo.valente@linaro.org> ha scritto:
>
>>
>> Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe <axboe@fb.com> ha scritto:
>>
>> This is basically identical to deadline-iosched, except it registers
>> as a MQ capable scheduler. This is still a single queue design.
>>
>
> Jens,
> no spin_lock_irq* in the code. So, also request dispatches are
> guaranteed to never be executed in IRQ context?

Or maybe the opposite? That is, all scheduler functions invoked in IRQ context?

Thanks,
Paolo

> I'm asking this
> question to understand whether I'm missing something that, even in
> BFQ, would somehow allow me to not disable irqs in critical sections,
> even if there is the slice_idle-expiration handler. Be patient with
> my ignorance.
>
> Thanks,
> Paolo
>
>> Signed-off-by: Jens Axboe <axboe@fb.com>
>> ---
>> block/Kconfig.iosched | 6 +
>> block/Makefile | 1 +
>> block/mq-deadline.c | 649 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 656 insertions(+)
>> create mode 100644 block/mq-deadline.c
>>
>> diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
>> index 421bef9c4c48..490ef2850fae 100644
>> --- a/block/Kconfig.iosched
>> +++ b/block/Kconfig.iosched
>> @@ -32,6 +32,12 @@ config IOSCHED_CFQ
>>
>> This is the default I/O scheduler.
>>
>> +config MQ_IOSCHED_DEADLINE
>> + tristate "MQ deadline I/O scheduler"
>> + default y
>> + ---help---
>> + MQ version of the deadline IO scheduler.
>> +
>> config CFQ_GROUP_IOSCHED
>> bool "CFQ Group Scheduling support"
>> depends on IOSCHED_CFQ && BLK_CGROUP
>> diff --git a/block/Makefile b/block/Makefile
>> index 2eee9e1bb6db..3ee0abd7205a 100644
>> --- a/block/Makefile
>> +++ b/block/Makefile
>> @@ -18,6 +18,7 @@ obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-throttle.o
>> obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
>> obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
>> obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
>> +obj-$(CONFIG_MQ_IOSCHED_DEADLINE) += mq-deadline.o
>>
>> obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
>> obj-$(CONFIG_BLK_CMDLINE_PARSER) += cmdline-parser.o
>> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
>> new file mode 100644
>> index 000000000000..3cb9de21ab21
>> --- /dev/null
>> +++ b/block/mq-deadline.c
>> @@ -0,0 +1,649 @@
>> +/*
>> + * MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
>> + * for the blk-mq scheduling framework
>> + *
>> + * Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/fs.h>
>> +#include <linux/blkdev.h>
>> +#include <linux/blk-mq.h>
>> +#include <linux/elevator.h>
>> +#include <linux/bio.h>
>> +#include <linux/module.h>
>> +#include <linux/slab.h>
>> +#include <linux/init.h>
>> +#include <linux/compiler.h>
>> +#include <linux/rbtree.h>
>> +#include <linux/sbitmap.h>
>> +
>> +#include "blk.h"
>> +#include "blk-mq.h"
>> +#include "blk-mq-tag.h"
>> +#include "blk-mq-sched.h"
>> +
>> +static unsigned int queue_depth = 256;
>> +module_param(queue_depth, uint, 0644);
>> +MODULE_PARM_DESC(queue_depth, "Use this value as the scheduler queue depth");
>> +
>> +/*
>> + * See Documentation/block/deadline-iosched.txt
>> + */
>> +static const int read_expire = HZ / 2; /* max time before a read is submitted. */
>> +static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
>> +static const int writes_starved = 2; /* max times reads can starve a write */
>> +static const int fifo_batch = 16; /* # of sequential requests treated as one
>> + by the above parameters. For throughput. */
>> +
>> +struct deadline_data {
>> + /*
>> + * run time data
>> + */
>> +
>> + /*
>> + * requests (deadline_rq s) are present on both sort_list and fifo_list
>> + */
>> + struct rb_root sort_list[2];
>> + struct list_head fifo_list[2];
>> +
>> + /*
>> + * next in sort order. read, write or both are NULL
>> + */
>> + struct request *next_rq[2];
>> + unsigned int batching; /* number of sequential requests made */
>> + unsigned int starved; /* times reads have starved writes */
>> +
>> + /*
>> + * settings that change how the i/o scheduler behaves
>> + */
>> + int fifo_expire[2];
>> + int fifo_batch;
>> + int writes_starved;
>> + int front_merges;
>> +
>> + spinlock_t lock;
>> + struct list_head dispatch;
>> + struct blk_mq_tags *tags;
>> + atomic_t wait_index;
>> +};
>> +
>> +static inline struct rb_root *
>> +deadline_rb_root(struct deadline_data *dd, struct request *rq)
>> +{
>> + return &dd->sort_list[rq_data_dir(rq)];
>> +}
>> +
>> +/*
>> + * get the request after `rq' in sector-sorted order
>> + */
>> +static inline struct request *
>> +deadline_latter_request(struct request *rq)
>> +{
>> + struct rb_node *node = rb_next(&rq->rb_node);
>> +
>> + if (node)
>> + return rb_entry_rq(node);
>> +
>> + return NULL;
>> +}
>> +
>> +static void
>> +deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
>> +{
>> + struct rb_root *root = deadline_rb_root(dd, rq);
>> +
>> + elv_rb_add(root, rq);
>> +}
>> +
>> +static inline void
>> +deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
>> +{
>> + const int data_dir = rq_data_dir(rq);
>> +
>> + if (dd->next_rq[data_dir] == rq)
>> + dd->next_rq[data_dir] = deadline_latter_request(rq);
>> +
>> + elv_rb_del(deadline_rb_root(dd, rq), rq);
>> +}
>> +
>> +/*
>> + * remove rq from rbtree and fifo.
>> + */
>> +static void deadline_remove_request(struct request_queue *q, struct request *rq)
>> +{
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> +
>> + list_del_init(&rq->queuelist);
>> +
>> + /*
>> + * We might not be on the rbtree, if we are doing an insert merge
>> + */
>> + if (!RB_EMPTY_NODE(&rq->rb_node))
>> + deadline_del_rq_rb(dd, rq);
>> +
>> + elv_rqhash_del(q, rq);
>> + if (q->last_merge == rq)
>> + q->last_merge = NULL;
>> +}
>> +
>> +static void dd_request_merged(struct request_queue *q, struct request *req,
>> + int type)
>> +{
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> +
>> + /*
>> + * if the merge was a front merge, we need to reposition request
>> + */
>> + if (type == ELEVATOR_FRONT_MERGE) {
>> + elv_rb_del(deadline_rb_root(dd, req), req);
>> + deadline_add_rq_rb(dd, req);
>> + }
>> +}
>> +
>> +static void dd_merged_requests(struct request_queue *q, struct request *req,
>> + struct request *next)
>> +{
>> + /*
>> + * if next expires before rq, assign its expire time to rq
>> + * and move into next position (next will be deleted) in fifo
>> + */
>> + if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
>> + if (time_before((unsigned long)next->fifo_time,
>> + (unsigned long)req->fifo_time)) {
>> + list_move(&req->queuelist, &next->queuelist);
>> + req->fifo_time = next->fifo_time;
>> + }
>> + }
>> +
>> + /*
>> + * kill knowledge of next, this one is a goner
>> + */
>> + deadline_remove_request(q, next);
>> +}
>> +
>> +/*
>> + * move an entry to dispatch queue
>> + */
>> +static void
>> +deadline_move_request(struct deadline_data *dd, struct request *rq)
>> +{
>> + const int data_dir = rq_data_dir(rq);
>> +
>> + dd->next_rq[READ] = NULL;
>> + dd->next_rq[WRITE] = NULL;
>> + dd->next_rq[data_dir] = deadline_latter_request(rq);
>> +
>> + /*
>> + * take it off the sort and fifo list
>> + */
>> + deadline_remove_request(rq->q, rq);
>> +}
>> +
>> +/*
>> + * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
>> + * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
>> + */
>> +static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
>> +{
>> + struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
>> +
>> + /*
>> + * rq is expired!
>> + */
>> + if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
>> + return 1;
>> +
>> + return 0;
>> +}
>> +
>> +/*
>> + * deadline_dispatch_requests selects the best request according to
>> + * read/write expire, fifo_batch, etc
>> + */
>> +static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
>> +{
>> + struct deadline_data *dd = hctx->queue->elevator->elevator_data;
>> + struct request *rq;
>> + bool reads, writes;
>> + int data_dir;
>> +
>> + spin_lock(&dd->lock);
>> +
>> + if (!list_empty(&dd->dispatch)) {
>> + rq = list_first_entry(&dd->dispatch, struct request, queuelist);
>> + list_del_init(&rq->queuelist);
>> + goto done;
>> + }
>> +
>> + reads = !list_empty(&dd->fifo_list[READ]);
>> + writes = !list_empty(&dd->fifo_list[WRITE]);
>> +
>> + /*
>> + * batches are currently reads XOR writes
>> + */
>> + if (dd->next_rq[WRITE])
>> + rq = dd->next_rq[WRITE];
>> + else
>> + rq = dd->next_rq[READ];
>> +
>> + if (rq && dd->batching < dd->fifo_batch)
>> + /* we have a next request are still entitled to batch */
>> + goto dispatch_request;
>> +
>> + /*
>> + * at this point we are not running a batch. select the appropriate
>> + * data direction (read / write)
>> + */
>> +
>> + if (reads) {
>> + BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
>> +
>> + if (writes && (dd->starved++ >= dd->writes_starved))
>> + goto dispatch_writes;
>> +
>> + data_dir = READ;
>> +
>> + goto dispatch_find_request;
>> + }
>> +
>> + /*
>> + * there are either no reads or writes have been starved
>> + */
>> +
>> + if (writes) {
>> +dispatch_writes:
>> + BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
>> +
>> + dd->starved = 0;
>> +
>> + data_dir = WRITE;
>> +
>> + goto dispatch_find_request;
>> + }
>> +
>> + spin_unlock(&dd->lock);
>> + return NULL;
>> +
>> +dispatch_find_request:
>> + /*
>> + * we are not running a batch, find best request for selected data_dir
>> + */
>> + if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
>> + /*
>> + * A deadline has expired, the last request was in the other
>> + * direction, or we have run out of higher-sectored requests.
>> + * Start again from the request with the earliest expiry time.
>> + */
>> + rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
>> + } else {
>> + /*
>> + * The last req was the same dir and we have a next request in
>> + * sort order. No expired requests so continue on from here.
>> + */
>> + rq = dd->next_rq[data_dir];
>> + }
>> +
>> + dd->batching = 0;
>> +
>> +dispatch_request:
>> + /*
>> + * rq is the selected appropriate request.
>> + */
>> + dd->batching++;
>> + deadline_move_request(dd, rq);
>> +done:
>> + rq->rq_flags |= RQF_STARTED;
>> + spin_unlock(&dd->lock);
>> + return rq;
>> +}
>> +
>> +static void dd_dispatch_requests(struct blk_mq_hw_ctx *hctx,
>> + struct list_head *rq_list)
>> +{
>> + blk_mq_sched_dispatch_shadow_requests(hctx, rq_list, __dd_dispatch_request);
>> +}
>> +
>> +static void dd_exit_queue(struct elevator_queue *e)
>> +{
>> + struct deadline_data *dd = e->elevator_data;
>> +
>> + BUG_ON(!list_empty(&dd->fifo_list[READ]));
>> + BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
>> +
>> + blk_mq_sched_free_requests(dd->tags);
>> + kfree(dd);
>> +}
>> +
>> +/*
>> + * initialize elevator private data (deadline_data).
>> + */
>> +static int dd_init_queue(struct request_queue *q, struct elevator_type *e)
>> +{
>> + struct deadline_data *dd;
>> + struct elevator_queue *eq;
>> +
>> + eq = elevator_alloc(q, e);
>> + if (!eq)
>> + return -ENOMEM;
>> +
>> + dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
>> + if (!dd) {
>> + kobject_put(&eq->kobj);
>> + return -ENOMEM;
>> + }
>> + eq->elevator_data = dd;
>> +
>> + dd->tags = blk_mq_sched_alloc_requests(queue_depth, q->node);
>> + if (!dd->tags) {
>> + kfree(dd);
>> + kobject_put(&eq->kobj);
>> + return -ENOMEM;
>> + }
>> +
>> + INIT_LIST_HEAD(&dd->fifo_list[READ]);
>> + INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
>> + dd->sort_list[READ] = RB_ROOT;
>> + dd->sort_list[WRITE] = RB_ROOT;
>> + dd->fifo_expire[READ] = read_expire;
>> + dd->fifo_expire[WRITE] = write_expire;
>> + dd->writes_starved = writes_starved;
>> + dd->front_merges = 1;
>> + dd->fifo_batch = fifo_batch;
>> + spin_lock_init(&dd->lock);
>> + INIT_LIST_HEAD(&dd->dispatch);
>> + atomic_set(&dd->wait_index, 0);
>> +
>> + q->elevator = eq;
>> + return 0;
>> +}
>> +
>> +static int dd_request_merge(struct request_queue *q, struct request **rq,
>> + struct bio *bio)
>> +{
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> + sector_t sector = bio_end_sector(bio);
>> + struct request *__rq;
>> +
>> + if (!dd->front_merges)
>> + return ELEVATOR_NO_MERGE;
>> +
>> + __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
>> + if (__rq) {
>> + BUG_ON(sector != blk_rq_pos(__rq));
>> +
>> + if (elv_bio_merge_ok(__rq, bio)) {
>> + *rq = __rq;
>> + return ELEVATOR_FRONT_MERGE;
>> + }
>> + }
>> +
>> + return ELEVATOR_NO_MERGE;
>> +}
>> +
>> +static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
>> +{
>> + struct request_queue *q = hctx->queue;
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> + int ret;
>> +
>> + spin_lock(&dd->lock);
>> + ret = blk_mq_sched_try_merge(q, bio);
>> + spin_unlock(&dd->lock);
>> +
>> + return ret;
>> +}
>> +
>> +/*
>> + * add rq to rbtree and fifo
>> + */
>> +static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>> + bool at_head)
>> +{
>> + struct request_queue *q = hctx->queue;
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> + const int data_dir = rq_data_dir(rq);
>> +
>> + if (blk_mq_sched_try_insert_merge(q, rq))
>> + return;
>> +
>> + blk_mq_sched_request_inserted(rq);
>> +
>> + /*
>> + * If we're trying to insert a real request, just send it directly
>> + * to the hardware dispatch list. This only happens for a requeue,
>> + * or FUA/FLUSH requests.
>> + */
>> + if (!blk_mq_sched_rq_is_shadow(rq)) {
>> + spin_lock(&hctx->lock);
>> + list_add_tail(&rq->queuelist, &hctx->dispatch);
>> + spin_unlock(&hctx->lock);
>> + return;
>> + }
>> +
>> + if (at_head || rq->cmd_type != REQ_TYPE_FS) {
>> + if (at_head)
>> + list_add(&rq->queuelist, &dd->dispatch);
>> + else
>> + list_add_tail(&rq->queuelist, &dd->dispatch);
>> + } else {
>> + deadline_add_rq_rb(dd, rq);
>> +
>> + if (rq_mergeable(rq)) {
>> + elv_rqhash_add(q, rq);
>> + if (!q->last_merge)
>> + q->last_merge = rq;
>> + }
>> +
>> + /*
>> + * set expire time and add to fifo list
>> + */
>> + rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
>> + list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
>> + }
>> +}
>> +
>> +static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
>> + struct list_head *list, bool at_head)
>> +{
>> + struct request_queue *q = hctx->queue;
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> +
>> + spin_lock(&dd->lock);
>> + while (!list_empty(list)) {
>> + struct request *rq;
>> +
>> + rq = list_first_entry(list, struct request, queuelist);
>> + list_del_init(&rq->queuelist);
>> + dd_insert_request(hctx, rq, at_head);
>> + }
>> + spin_unlock(&dd->lock);
>> +}
>> +
>> +static struct request *dd_get_request(struct request_queue *q, unsigned int op,
>> + struct blk_mq_alloc_data *data)
>> +{
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> + struct request *rq;
>> +
>> + /*
>> + * The flush machinery intercepts before we insert the request. As
>> + * a work-around, just hand it back a real request.
>> + */
>> + if (unlikely(op & (REQ_PREFLUSH | REQ_FUA)))
>> + rq = __blk_mq_alloc_request(data, op);
>> + else {
>> + rq = blk_mq_sched_alloc_shadow_request(q, data, dd->tags, &dd->wait_index);
>> + if (rq)
>> + blk_mq_rq_ctx_init(q, data->ctx, rq, op);
>> + }
>> +
>> + return rq;
>> +}
>> +
>> +static bool dd_put_request(struct request *rq)
>> +{
>> + /*
>> + * If it's a real request, we just have to free it. For a shadow
>> + * request, we should only free it if we haven't started it. A
>> + * started request is mapped to a real one, and the real one will
>> + * free it. We can get here with request merges, since we then
>> + * free the request before we start/issue it.
>> + */
>> + if (!blk_mq_sched_rq_is_shadow(rq))
>> + return false;
>> +
>> + if (!(rq->rq_flags & RQF_STARTED)) {
>> + struct request_queue *q = rq->q;
>> + struct deadline_data *dd = q->elevator->elevator_data;
>> +
>> + /*
>> + * IO completion would normally do this, but if we merge
>> + * and free before we issue the request, drop both the
>> + * tag and queue ref
>> + */
>> + blk_mq_sched_free_shadow_request(dd->tags, rq);
>> + blk_queue_exit(q);
>> + }
>> +
>> + return true;
>> +}
>> +
>> +static void dd_completed_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
>> +{
>> + struct request *sched_rq = rq->end_io_data;
>> +
>> + /*
>> + * sched_rq can be NULL, if we haven't setup the shadow yet
>> + * because we failed getting one.
>> + */
>> + if (sched_rq) {
>> + struct deadline_data *dd = hctx->queue->elevator->elevator_data;
>> +
>> + blk_mq_sched_free_shadow_request(dd->tags, sched_rq);
>> + blk_mq_start_stopped_hw_queue(hctx, true);
>> + }
>> +}
>> +
>> +static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
>> +{
>> + struct deadline_data *dd = hctx->queue->elevator->elevator_data;
>> +
>> + return !list_empty_careful(&dd->dispatch) ||
>> + !list_empty_careful(&dd->fifo_list[0]) ||
>> + !list_empty_careful(&dd->fifo_list[1]);
>> +}
>> +
>> +/*
>> + * sysfs parts below
>> + */
>> +static ssize_t
>> +deadline_var_show(int var, char *page)
>> +{
>> + return sprintf(page, "%d\n", var);
>> +}
>> +
>> +static ssize_t
>> +deadline_var_store(int *var, const char *page, size_t count)
>> +{
>> + char *p = (char *) page;
>> +
>> + *var = simple_strtol(p, &p, 10);
>> + return count;
>> +}
>> +
>> +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
>> +static ssize_t __FUNC(struct elevator_queue *e, char *page) \
>> +{ \
>> + struct deadline_data *dd = e->elevator_data; \
>> + int __data = __VAR; \
>> + if (__CONV) \
>> + __data = jiffies_to_msecs(__data); \
>> + return deadline_var_show(__data, (page)); \
>> +}
>> +SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
>> +SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
>> +SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
>> +SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
>> +SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
>> +#undef SHOW_FUNCTION
>> +
>> +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
>> +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
>> +{ \
>> + struct deadline_data *dd = e->elevator_data; \
>> + int __data; \
>> + int ret = deadline_var_store(&__data, (page), count); \
>> + if (__data < (MIN)) \
>> + __data = (MIN); \
>> + else if (__data > (MAX)) \
>> + __data = (MAX); \
>> + if (__CONV) \
>> + *(__PTR) = msecs_to_jiffies(__data); \
>> + else \
>> + *(__PTR) = __data; \
>> + return ret; \
>> +}
>> +STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
>> +STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
>> +STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
>> +STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
>> +STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
>> +#undef STORE_FUNCTION
>> +
>> +#define DD_ATTR(name) \
>> + __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
>> + deadline_##name##_store)
>> +
>> +static struct elv_fs_entry deadline_attrs[] = {
>> + DD_ATTR(read_expire),
>> + DD_ATTR(write_expire),
>> + DD_ATTR(writes_starved),
>> + DD_ATTR(front_merges),
>> + DD_ATTR(fifo_batch),
>> + __ATTR_NULL
>> +};
>> +
>> +static struct elevator_type mq_deadline = {
>> + .ops.mq = {
>> + .get_request = dd_get_request,
>> + .put_request = dd_put_request,
>> + .insert_requests = dd_insert_requests,
>> + .dispatch_requests = dd_dispatch_requests,
>> + .completed_request = dd_completed_request,
>> + .next_request = elv_rb_latter_request,
>> + .former_request = elv_rb_former_request,
>> + .bio_merge = dd_bio_merge,
>> + .request_merge = dd_request_merge,
>> + .requests_merged = dd_merged_requests,
>> + .request_merged = dd_request_merged,
>> + .has_work = dd_has_work,
>> + .init_sched = dd_init_queue,
>> + .exit_sched = dd_exit_queue,
>> + },
>> +
>> + .uses_mq = true,
>> + .elevator_attrs = deadline_attrs,
>> + .elevator_name = "mq-deadline",
>> + .elevator_owner = THIS_MODULE,
>> +};
>> +
>> +static int __init deadline_init(void)
>> +{
>> + if (!queue_depth) {
>> + pr_err("mq-deadline: queue depth must be > 0\n");
>> + return -EINVAL;
>> + }
>> + return elv_register(&mq_deadline);
>> +}
>> +
>> +static void __exit deadline_exit(void)
>> +{
>> + elv_unregister(&mq_deadline);
>> +}
>> +
>> +module_init(deadline_init);
>> +module_exit(deadline_exit);
>> +
>> +MODULE_AUTHOR("Jens Axboe");
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("MQ deadline IO scheduler");
>> --
>> 2.7.4
>>
>> --
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