linux-stable/block/elevator.c
James Bottomley fa0ccd837e block: implement drain buffers
These DMA drain buffer implementations in drivers are pretty horrible
to do in terms of manipulating the scatterlist.  Plus they're being
done at least in drivers/ide and drivers/ata, so we now have code
duplication.

The one use case for this, as I understand it is AHCI controllers doing
PIO mode to mmc devices but translating this to DMA at the controller
level.

So, what about adding a callback to the block layer that permits the
adding of the drain buffer for the problem devices.  The idea is that
you'd do this in slave_configure after you find one of these devices.

The beauty of doing it in the block layer is that it quietly adds the
drain buffer to the end of the sg list, so it automatically gets mapped
(and unmapped) without anything unusual having to be done to the
scatterlist in driver/scsi or drivers/ata and without any alteration to
the transfer length.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 10:54:11 +01:00

1177 lines
26 KiB
C

/*
* 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 <asm/uaccess.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?
*/
inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
{
if (!rq_mergeable(rq))
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;
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 && !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)))
return -EINVAL;
if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
printk("I/O scheduler %s not found\n", chosen_elevator);
if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
printk("Default I/O scheduler not found, using no-op\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;
if (q->last_merge == rq)
q->last_merge = NULL;
elv_rqhash_del(q, rq);
q->nr_sorted--;
boundary = q->end_sector;
list_for_each_prev(entry, &q->queue_head) {
struct request *pos = list_entry_rq(entry);
if (rq_data_dir(rq) != rq_data_dir(pos))
break;
if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
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;
}
}
/*
* 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));
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",
__FUNCTION__, 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)) {
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)) {
end_queued_request(rq, 1);
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);
}
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++;
rq->nr_hw_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->nr_hw_segments;
}
rq = NULL;
break;
} else if (ret == BLKPREP_KILL) {
rq->cmd_flags |= REQ_QUIET;
end_queued_request(rq, 0);
} else {
printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
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_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);
set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
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);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
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);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
return 0;
}
ssize_t elv_iosched_store(struct request_queue *q, const char *name,
size_t count)
{
char elevator_name[ELV_NAME_MAX];
size_t len;
struct elevator_type *e;
elevator_name[sizeof(elevator_name) - 1] = '\0';
strncpy(elevator_name, name, sizeof(elevator_name) - 1);
len = strlen(elevator_name);
if (len && elevator_name[len - 1] == '\n')
elevator_name[len - 1] = '\0';
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);