original development tree for Linux kernel GTP module; now long in mainline.
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/*
* Block device elevator/IO-scheduler.
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
*
* 30042000 Jens Axboe <axboe@kernel.dk> :
*
* Split the elevator a bit so that it is possible to choose a different
* one or even write a new "plug in". There are three pieces:
* - elevator_fn, inserts a new request in the queue list
* - elevator_merge_fn, decides whether a new buffer can be merged with
* an existing request
* - elevator_dequeue_fn, called when a request is taken off the active list
*
* 20082000 Dave Jones <davej@suse.de> :
* Removed tests for max-bomb-segments, which was breaking elvtune
* when run without -bN
*
* Jens:
* - Rework again to work with bio instead of buffer_heads
* - loose bi_dev comparisons, partition handling is right now
* - completely modularize elevator setup and teardown
*
*/
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/blkdev.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/delay.h>
#include <linux/blktrace_api.h>
#include <linux/hash.h>
#include <linux/uaccess.h>
#include "blk.h"
static DEFINE_SPINLOCK(elv_list_lock);
static LIST_HEAD(elv_list);
/*
* Merge hash stuff.
*/
static const int elv_hash_shift = 6;
#define ELV_HASH_BLOCK(sec) ((sec) >> 3)
#define ELV_HASH_FN(sec) \
(hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
#define ELV_HASH_ENTRIES (1 << elv_hash_shift)
#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
#define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash))
/*
* Query io scheduler to see if the current process issuing bio may be
* merged with rq.
*/
static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
{
struct request_queue *q = rq->q;
elevator_t *e = q->elevator;
if (e->ops->elevator_allow_merge_fn)
return e->ops->elevator_allow_merge_fn(q, rq, bio);
return 1;
}
/*
* can we safely merge with this request?
*/
int elv_rq_merge_ok(struct request *rq, struct bio *bio)
{
if (!rq_mergeable(rq))
return 0;
/*
* Don't merge file system requests and discard requests
*/
if (bio_discard(bio) != bio_discard(rq->bio))
return 0;
/*
* different data direction or already started, don't merge
*/
if (bio_data_dir(bio) != rq_data_dir(rq))
return 0;
/*
* must be same device and not a special request
*/
if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
return 0;
/*
* only merge integrity protected bio into ditto rq
*/
if (bio_integrity(bio) != blk_integrity_rq(rq))
return 0;
if (!elv_iosched_allow_merge(rq, bio))
return 0;
return 1;
}
EXPORT_SYMBOL(elv_rq_merge_ok);
static inline int elv_try_merge(struct request *__rq, struct bio *bio)
{
int ret = ELEVATOR_NO_MERGE;
/*
* we can merge and sequence is ok, check if it's possible
*/
if (elv_rq_merge_ok(__rq, bio)) {
if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
ret = ELEVATOR_BACK_MERGE;
else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
ret = ELEVATOR_FRONT_MERGE;
}
return ret;
}
static struct elevator_type *elevator_find(const char *name)
{
struct elevator_type *e;
list_for_each_entry(e, &elv_list, list) {
if (!strcmp(e->elevator_name, name))
return e;
}
return NULL;
}
static void elevator_put(struct elevator_type *e)
{
module_put(e->elevator_owner);
}
static struct elevator_type *elevator_get(const char *name)
{
struct elevator_type *e;
spin_lock(&elv_list_lock);
e = elevator_find(name);
if (!e) {
char elv[ELV_NAME_MAX + strlen("-iosched")];
spin_unlock(&elv_list_lock);
if (!strcmp(name, "anticipatory"))
sprintf(elv, "as-iosched");
else
sprintf(elv, "%s-iosched", name);
request_module("%s", elv);
spin_lock(&elv_list_lock);
e = elevator_find(name);
}
if (e && !try_module_get(e->elevator_owner))
e = NULL;
spin_unlock(&elv_list_lock);
return e;
}
static void *elevator_init_queue(struct request_queue *q,
struct elevator_queue *eq)
{
return eq->ops->elevator_init_fn(q);
}
static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
void *data)
{
q->elevator = eq;
eq->elevator_data = data;
}
static char chosen_elevator[16];
static int __init elevator_setup(char *str)
{
/*
* Be backwards-compatible with previous kernels, so users
* won't get the wrong elevator.
*/
if (!strcmp(str, "as"))
strcpy(chosen_elevator, "anticipatory");
else
strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
return 1;
}
__setup("elevator=", elevator_setup);
static struct kobj_type elv_ktype;
static elevator_t *elevator_alloc(struct request_queue *q,
struct elevator_type *e)
{
elevator_t *eq;
int i;
eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL | __GFP_ZERO, q->node);
if (unlikely(!eq))
goto err;
eq->ops = &e->ops;
eq->elevator_type = e;
kobject_init(&eq->kobj, &elv_ktype);
mutex_init(&eq->sysfs_lock);
eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
GFP_KERNEL, q->node);
if (!eq->hash)
goto err;
for (i = 0; i < ELV_HASH_ENTRIES; i++)
INIT_HLIST_HEAD(&eq->hash[i]);
return eq;
err:
kfree(eq);
elevator_put(e);
return NULL;
}
static void elevator_release(struct kobject *kobj)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
elevator_put(e->elevator_type);
kfree(e->hash);
kfree(e);
}
int elevator_init(struct request_queue *q, char *name)
{
struct elevator_type *e = NULL;
struct elevator_queue *eq;
int ret = 0;
void *data;
INIT_LIST_HEAD(&q->queue_head);
q->last_merge = NULL;
q->end_sector = 0;
q->boundary_rq = NULL;
if (name) {
e = elevator_get(name);
if (!e)
return -EINVAL;
}
if (!e && *chosen_elevator) {
e = elevator_get(chosen_elevator);
if (!e)
printk(KERN_ERR "I/O scheduler %s not found\n",
chosen_elevator);
}
if (!e) {
e = elevator_get(CONFIG_DEFAULT_IOSCHED);
if (!e) {
printk(KERN_ERR
"Default I/O scheduler not found. " \
"Using noop.\n");
e = elevator_get("noop");
}
}
eq = elevator_alloc(q, e);
if (!eq)
return -ENOMEM;
data = elevator_init_queue(q, eq);
if (!data) {
kobject_put(&eq->kobj);
return -ENOMEM;
}
elevator_attach(q, eq, data);
return ret;
}
EXPORT_SYMBOL(elevator_init);
void elevator_exit(elevator_t *e)
{
mutex_lock(&e->sysfs_lock);
if (e->ops->elevator_exit_fn)
e->ops->elevator_exit_fn(e);
e->ops = NULL;
mutex_unlock(&e->sysfs_lock);
kobject_put(&e->kobj);
}
EXPORT_SYMBOL(elevator_exit);
static void elv_activate_rq(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_activate_req_fn)
e->ops->elevator_activate_req_fn(q, rq);
}
static void elv_deactivate_rq(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_deactivate_req_fn)
e->ops->elevator_deactivate_req_fn(q, rq);
}
static inline void __elv_rqhash_del(struct request *rq)
{
hlist_del_init(&rq->hash);
}
static void elv_rqhash_del(struct request_queue *q, struct request *rq)
{
if (ELV_ON_HASH(rq))
__elv_rqhash_del(rq);
}
static void elv_rqhash_add(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
BUG_ON(ELV_ON_HASH(rq));
hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
}
static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
{
__elv_rqhash_del(rq);
elv_rqhash_add(q, rq);
}
static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
{
elevator_t *e = q->elevator;
struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
struct hlist_node *entry, *next;
struct request *rq;
hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
BUG_ON(!ELV_ON_HASH(rq));
if (unlikely(!rq_mergeable(rq))) {
__elv_rqhash_del(rq);
continue;
}
if (rq_hash_key(rq) == offset)
return rq;
}
return NULL;
}
/*
* RB-tree support functions for inserting/lookup/removal of requests
* in a sorted RB tree.
*/
struct request *elv_rb_add(struct rb_root *root, struct request *rq)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct request *__rq;
while (*p) {
parent = *p;
__rq = rb_entry(parent, struct request, rb_node);
if (rq->sector < __rq->sector)
p = &(*p)->rb_left;
else if (rq->sector > __rq->sector)
p = &(*p)->rb_right;
else
return __rq;
}
rb_link_node(&rq->rb_node, parent, p);
rb_insert_color(&rq->rb_node, root);
return NULL;
}
EXPORT_SYMBOL(elv_rb_add);
void elv_rb_del(struct rb_root *root, struct request *rq)
{
BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
rb_erase(&rq->rb_node, root);
RB_CLEAR_NODE(&rq->rb_node);
}
EXPORT_SYMBOL(elv_rb_del);
struct request *elv_rb_find(struct rb_root *root, sector_t sector)
{
struct rb_node *n = root->rb_node;
struct request *rq;
while (n) {
rq = rb_entry(n, struct request, rb_node);
if (sector < rq->sector)
n = n->rb_left;
else if (sector > rq->sector)
n = n->rb_right;
else
return rq;
}
return NULL;
}
EXPORT_SYMBOL(elv_rb_find);
/*
* Insert rq into dispatch queue of q. Queue lock must be held on
* entry. rq is sort instead into the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_sort(struct request_queue *q, struct request *rq)
{
sector_t boundary;
struct list_head *entry;
int stop_flags;
if (q->last_merge == rq)
q->last_merge = NULL;
elv_rqhash_del(q, rq);
q->nr_sorted--;
boundary = q->end_sector;
stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
list_for_each_prev(entry, &q->queue_head) {
struct request *pos = list_entry_rq(entry);
if (blk_discard_rq(rq) != blk_discard_rq(pos))
break;
if (rq_data_dir(rq) != rq_data_dir(pos))
break;
if (pos->cmd_flags & stop_flags)
break;
if (rq->sector >= boundary) {
if (pos->sector < boundary)
continue;
} else {
if (pos->sector >= boundary)
break;
}
if (rq->sector >= pos->sector)
break;
}
list_add(&rq->queuelist, entry);
}
EXPORT_SYMBOL(elv_dispatch_sort);
/*
* Insert rq into dispatch queue of q. Queue lock must be held on
* entry. rq is added to the back of the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
{
if (q->last_merge == rq)
q->last_merge = NULL;
elv_rqhash_del(q, rq);
q->nr_sorted--;
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;
list_add_tail(&rq->queuelist, &q->queue_head);
}
EXPORT_SYMBOL(elv_dispatch_add_tail);
int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
{
elevator_t *e = q->elevator;
struct request *__rq;
int ret;
/*
* First try one-hit cache.
*/
if (q->last_merge) {
ret = elv_try_merge(q->last_merge, bio);
if (ret != ELEVATOR_NO_MERGE) {
*req = q->last_merge;
return ret;
}
}
if (blk_queue_nomerges(q))
return ELEVATOR_NO_MERGE;
/*
* See if our hash lookup can find a potential backmerge.
*/
__rq = elv_rqhash_find(q, bio->bi_sector);
if (__rq && elv_rq_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_BACK_MERGE;
}
if (e->ops->elevator_merge_fn)
return e->ops->elevator_merge_fn(q, req, bio);
return ELEVATOR_NO_MERGE;
}
void elv_merged_request(struct request_queue *q, struct request *rq, int type)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_merged_fn)
e->ops->elevator_merged_fn(q, rq, type);
if (type == ELEVATOR_BACK_MERGE)
elv_rqhash_reposition(q, rq);
q->last_merge = rq;
}
void elv_merge_requests(struct request_queue *q, struct request *rq,
struct request *next)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_merge_req_fn)
e->ops->elevator_merge_req_fn(q, rq, next);
elv_rqhash_reposition(q, rq);
elv_rqhash_del(q, next);
q->nr_sorted--;
q->last_merge = rq;
}
void elv_requeue_request(struct request_queue *q, struct request *rq)
{
/*
* it already went through dequeue, we need to decrement the
* in_flight count again
*/
if (blk_account_rq(rq)) {
q->in_flight--;
if (blk_sorted_rq(rq))
elv_deactivate_rq(q, rq);
}
rq->cmd_flags &= ~REQ_STARTED;
elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
}
static void elv_drain_elevator(struct request_queue *q)
{
static int printed;
while (q->elevator->ops->elevator_dispatch_fn(q, 1))
;
if (q->nr_sorted == 0)
return;
if (printed++ < 10) {
printk(KERN_ERR "%s: forced dispatching is broken "
"(nr_sorted=%u), please report this\n",
q->elevator->elevator_type->elevator_name, q->nr_sorted);
}
}
void elv_insert(struct request_queue *q, struct request *rq, int where)
{
struct list_head *pos;
unsigned ordseq;
int unplug_it = 1;
blk_add_trace_rq(q, rq, BLK_TA_INSERT);
rq->q = q;
switch (where) {
case ELEVATOR_INSERT_FRONT:
rq->cmd_flags |= REQ_SOFTBARRIER;
list_add(&rq->queuelist, &q->queue_head);
break;
case ELEVATOR_INSERT_BACK:
rq->cmd_flags |= REQ_SOFTBARRIER;
elv_drain_elevator(q);
list_add_tail(&rq->queuelist, &q->queue_head);
/*
* We kick the queue here for the following reasons.
* - The elevator might have returned NULL previously
* to delay requests and returned them now. As the
* queue wasn't empty before this request, ll_rw_blk
* won't run the queue on return, resulting in hang.
* - Usually, back inserted requests won't be merged
* with anything. There's no point in delaying queue
* processing.
*/
blk_remove_plug(q);
q->request_fn(q);
break;
case ELEVATOR_INSERT_SORT:
BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));
rq->cmd_flags |= REQ_SORTED;
q->nr_sorted++;
if (rq_mergeable(rq)) {
elv_rqhash_add(q, rq);
if (!q->last_merge)
q->last_merge = rq;
}
/*
* Some ioscheds (cfq) run q->request_fn directly, so
* rq cannot be accessed after calling
* elevator_add_req_fn.
*/
q->elevator->ops->elevator_add_req_fn(q, rq);
break;
case ELEVATOR_INSERT_REQUEUE:
/*
* If ordered flush isn't in progress, we do front
* insertion; otherwise, requests should be requeued
* in ordseq order.
*/
rq->cmd_flags |= REQ_SOFTBARRIER;
/*
* Most requeues happen because of a busy condition,
* don't force unplug of the queue for that case.
*/
unplug_it = 0;
if (q->ordseq == 0) {
list_add(&rq->queuelist, &q->queue_head);
break;
}
ordseq = blk_ordered_req_seq(rq);
list_for_each(pos, &q->queue_head) {
struct request *pos_rq = list_entry_rq(pos);
if (ordseq <= blk_ordered_req_seq(pos_rq))
break;
}
list_add_tail(&rq->queuelist, pos);
break;
default:
printk(KERN_ERR "%s: bad insertion point %d\n",
__func__, where);
BUG();
}
if (unplug_it && blk_queue_plugged(q)) {
int nrq = q->rq.count[READ] + q->rq.count[WRITE]
- q->in_flight;
if (nrq >= q->unplug_thresh)
__generic_unplug_device(q);
}
}
void __elv_add_request(struct request_queue *q, struct request *rq, int where,
int plug)
{
if (q->ordcolor)
rq->cmd_flags |= REQ_ORDERED_COLOR;
if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
/*
* toggle ordered color
*/
if (blk_barrier_rq(rq))
q->ordcolor ^= 1;
/*
* barriers implicitly indicate back insertion
*/
if (where == ELEVATOR_INSERT_SORT)
where = ELEVATOR_INSERT_BACK;
/*
* this request is scheduling boundary, update
* end_sector
*/
if (blk_fs_request(rq) || blk_discard_rq(rq)) {
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;
}
} else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
where == ELEVATOR_INSERT_SORT)
where = ELEVATOR_INSERT_BACK;
if (plug)
blk_plug_device(q);
elv_insert(q, rq, where);
}
EXPORT_SYMBOL(__elv_add_request);
void elv_add_request(struct request_queue *q, struct request *rq, int where,
int plug)
{
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
__elv_add_request(q, rq, where, plug);
spin_unlock_irqrestore(q->queue_lock, flags);
}
EXPORT_SYMBOL(elv_add_request);
static inline struct request *__elv_next_request(struct request_queue *q)
{
struct request *rq;
while (1) {
while (!list_empty(&q->queue_head)) {
rq = list_entry_rq(q->queue_head.next);
if (blk_do_ordered(q, &rq))
return rq;
}
if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
return NULL;
}
}
struct request *elv_next_request(struct request_queue *q)
{
struct request *rq;
int ret;
while ((rq = __elv_next_request(q)) != NULL) {
/*
* Kill the empty barrier place holder, the driver must
* not ever see it.
*/
if (blk_empty_barrier(rq)) {
__blk_end_request(rq, 0, blk_rq_bytes(rq));
continue;
}
if (!(rq->cmd_flags & REQ_STARTED)) {
/*
* This is the first time the device driver
* sees this request (possibly after
* requeueing). Notify IO scheduler.
*/
if (blk_sorted_rq(rq))
elv_activate_rq(q, rq);
/*
* just mark as started even if we don't start
* it, a request that has been delayed should
* not be passed by new incoming requests
*/
rq->cmd_flags |= REQ_STARTED;
blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
/*
* We are now handing the request to the hardware,
* add the timeout handler
*/
blk_add_timer(rq);
}
if (!q->boundary_rq || q->boundary_rq == rq) {
q->end_sector = rq_end_sector(rq);
q->boundary_rq = NULL;
}
if (rq->cmd_flags & REQ_DONTPREP)
break;
if (q->dma_drain_size && rq->data_len) {
/*
* make sure space for the drain appears we
* know we can do this because max_hw_segments
* has been adjusted to be one fewer than the
* device can handle
*/
rq->nr_phys_segments++;
}
if (!q->prep_rq_fn)
break;
ret = q->prep_rq_fn(q, rq);
if (ret == BLKPREP_OK) {
break;
} else if (ret == BLKPREP_DEFER) {
/*
* the request may have been (partially) prepped.
* we need to keep this request in the front to
* avoid resource deadlock. REQ_STARTED will
* prevent other fs requests from passing this one.
*/
if (q->dma_drain_size && rq->data_len &&
!(rq->cmd_flags & REQ_DONTPREP)) {
/*
* remove the space for the drain we added
* so that we don't add it again
*/
--rq->nr_phys_segments;
}
rq = NULL;
break;
} else if (ret == BLKPREP_KILL) {
rq->cmd_flags |= REQ_QUIET;
__blk_end_request(rq, -EIO, blk_rq_bytes(rq));
} else {
printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
break;
}
}
return rq;
}
EXPORT_SYMBOL(elv_next_request);
void elv_dequeue_request(struct request_queue *q, struct request *rq)
{
BUG_ON(list_empty(&rq->queuelist));
BUG_ON(ELV_ON_HASH(rq));
list_del_init(&rq->queuelist);
/*
* the time frame between a request being removed from the lists
* and to it is freed is accounted as io that is in progress at
* the driver side.
*/
if (blk_account_rq(rq))
q->in_flight++;
}
EXPORT_SYMBOL(elv_dequeue_request);
int elv_queue_empty(struct request_queue *q)
{
elevator_t *e = q->elevator;
if (!list_empty(&q->queue_head))
return 0;
if (e->ops->elevator_queue_empty_fn)
return e->ops->elevator_queue_empty_fn(q);
return 1;
}
EXPORT_SYMBOL(elv_queue_empty);
struct request *elv_latter_request(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_latter_req_fn)
return e->ops->elevator_latter_req_fn(q, rq);
return NULL;
}
struct request *elv_former_request(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_former_req_fn)
return e->ops->elevator_former_req_fn(q, rq);
return NULL;
}
int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_set_req_fn)
return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
rq->elevator_private = NULL;
return 0;
}
void elv_put_request(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_put_req_fn)
e->ops->elevator_put_req_fn(rq);
}
int elv_may_queue(struct request_queue *q, int rw)
{
elevator_t *e = q->elevator;
if (e->ops->elevator_may_queue_fn)
return e->ops->elevator_may_queue_fn(q, rw);
return ELV_MQUEUE_MAY;
}
void elv_abort_queue(struct request_queue *q)
{
struct request *rq;
while (!list_empty(&q->queue_head)) {
rq = list_entry_rq(q->queue_head.next);
rq->cmd_flags |= REQ_QUIET;
blk_add_trace_rq(q, rq, BLK_TA_ABORT);
__blk_end_request(rq, -EIO, blk_rq_bytes(rq));
}
}
EXPORT_SYMBOL(elv_abort_queue);
void elv_completed_request(struct request_queue *q, struct request *rq)
{
elevator_t *e = q->elevator;
/*
* request is released from the driver, io must be done
*/
if (blk_account_rq(rq)) {
q->in_flight--;
if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
e->ops->elevator_completed_req_fn(q, rq);
}
/*
* Check if the queue is waiting for fs requests to be
* drained for flush sequence.
*/
if (unlikely(q->ordseq)) {
struct request *first_rq = list_entry_rq(q->queue_head.next);
if (q->in_flight == 0 &&
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
q->request_fn(q);
}
}
}
#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
static ssize_t
elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct elv_fs_entry *entry = to_elv(attr);
ssize_t error;
if (!entry->show)
return -EIO;
mutex_lock(&e->sysfs_lock);
error = e->ops ? entry->show(e, page) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static ssize_t
elv_attr_store(struct kobject *kobj, struct attribute *attr,
const char *page, size_t length)
{
elevator_t *e = container_of(kobj, elevator_t, kobj);
struct elv_fs_entry *entry = to_elv(attr);
ssize_t error;
if (!entry->store)
return -EIO;
mutex_lock(&e->sysfs_lock);
error = e->ops ? entry->store(e, page, length) : -ENOENT;
mutex_unlock(&e->sysfs_lock);
return error;
}
static struct sysfs_ops elv_sysfs_ops = {
.show = elv_attr_show,
.store = elv_attr_store,
};
static struct kobj_type elv_ktype = {
.sysfs_ops = &elv_sysfs_ops,
.release = elevator_release,
};
int elv_register_queue(struct request_queue *q)
{
elevator_t *e = q->elevator;
int error;
error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
if (!error) {
struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
if (attr) {
while (attr->attr.name) {
if (sysfs_create_file(&e->kobj, &attr->attr))
break;
attr++;
}
}
kobject_uevent(&e->kobj, KOBJ_ADD);
}
return error;
}
static void __elv_unregister_queue(elevator_t *e)
{
kobject_uevent(&e->kobj, KOBJ_REMOVE);
kobject_del(&e->kobj);
}
void elv_unregister_queue(struct request_queue *q)
{
if (q)
__elv_unregister_queue(q->elevator);
}
void elv_register(struct elevator_type *e)
{
char *def = "";
spin_lock(&elv_list_lock);
BUG_ON(elevator_find(e->elevator_name));
list_add_tail(&e->list, &elv_list);
spin_unlock(&elv_list_lock);
if (!strcmp(e->elevator_name, chosen_elevator) ||
(!*chosen_elevator &&
!strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
def = " (default)";
printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
def);
}
EXPORT_SYMBOL_GPL(elv_register);
void elv_unregister(struct elevator_type *e)
{
struct task_struct *g, *p;
/*
* Iterate every thread in the process to remove the io contexts.
*/
if (e->ops.trim) {
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
if (p->io_context)
e->ops.trim(p->io_context);
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}
spin_lock(&elv_list_lock);
list_del_init(&e->list);
spin_unlock(&elv_list_lock);
}
EXPORT_SYMBOL_GPL(elv_unregister);
/*
* switch to new_e io scheduler. be careful not to introduce deadlocks -
* we don't free the old io scheduler, before we have allocated what we
* need for the new one. this way we have a chance of going back to the old
* one, if the new one fails init for some reason.
*/
static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
{
elevator_t *old_elevator, *e;
void *data;
/*
* Allocate new elevator
*/
e = elevator_alloc(q, new_e);
if (!e)
return 0;
data = elevator_init_queue(q, e);
if (!data) {
kobject_put(&e->kobj);
return 0;
}
/*
* Turn on BYPASS and drain all requests w/ elevator private data
*/
spin_lock_irq(q->queue_lock);
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
elv_drain_elevator(q);
while (q->rq.elvpriv) {
blk_remove_plug(q);
q->request_fn(q);
spin_unlock_irq(q->queue_lock);
msleep(10);
spin_lock_irq(q->queue_lock);
elv_drain_elevator(q);
}
/*
* Remember old elevator.
*/
old_elevator = q->elevator;
/*
* attach and start new elevator
*/
elevator_attach(q, e, data);
spin_unlock_irq(q->queue_lock);
__elv_unregister_queue(old_elevator);
if (elv_register_queue(q))
goto fail_register;
/*
* finally exit old elevator and turn off BYPASS.
*/
elevator_exit(old_elevator);
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
return 1;
fail_register:
/*
* switch failed, exit the new io scheduler and reattach the old
* one again (along with re-adding the sysfs dir)
*/
elevator_exit(e);
q->elevator = old_elevator;
elv_register_queue(q);
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
return 0;
}
ssize_t elv_iosched_store(struct request_queue *q, const char *name,
size_t count)
{
char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
strlcpy(elevator_name, name, sizeof(elevator_name));
strstrip(elevator_name);
e = elevator_get(elevator_name);
if (!e) {
printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
return -EINVAL;
}
if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
elevator_put(e);
return count;
}
if (!elevator_switch(q, e))
printk(KERN_ERR "elevator: switch to %s failed\n",
elevator_name);
return count;
}
ssize_t elv_iosched_show(struct request_queue *q, char *name)
{
elevator_t *e = q->elevator;
struct elevator_type *elv = e->elevator_type;
struct elevator_type *__e;
int len = 0;
spin_lock(&elv_list_lock);
list_for_each_entry(__e, &elv_list, list) {
if (!strcmp(elv->elevator_name, __e->elevator_name))
len += sprintf(name+len, "[%s] ", elv->elevator_name);
else
len += sprintf(name+len, "%s ", __e->elevator_name);
}
spin_unlock(&elv_list_lock);
len += sprintf(len+name, "\n");
return len;
}
struct request *elv_rb_former_request(struct request_queue *q,
struct request *rq)
{
struct rb_node *rbprev = rb_prev(&rq->rb_node);
if (rbprev)
return rb_entry_rq(rbprev);
return NULL;
}
EXPORT_SYMBOL(elv_rb_former_request);
struct request *elv_rb_latter_request(struct request_queue *q,
struct request *rq)
{
struct rb_node *rbnext = rb_next(&rq->rb_node);
if (rbnext)
return rb_entry_rq(rbnext);
return NULL;
}
EXPORT_SYMBOL(elv_rb_latter_request);