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block: reorganize request fetching functions
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Impact: code reorganization

elv_next_request() and elv_dequeue_request() are public block layer
interface than actual elevator implementation.  They mostly deal with
how requests interact with block layer and low level drivers at the
beginning of rqeuest processing whereas __elv_next_request() is the
actual eleveator request fetching interface.

Move the two functions to blk-core.c.  This prepares for further
interface cleanup.

Signed-off-by: Tejun Heo <tj@kernel.org>
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@htejun
htejun authored and Jens Axboe committed Apr 28, 2009
1 parent 5efccd1 commit 158dbda
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Showing 3 changed files with 132 additions and 128 deletions.
95 changes: 95 additions & 0 deletions block/blk-core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1712,6 +1712,101 @@ unsigned int blk_rq_cur_bytes(struct request *rq)
}
EXPORT_SYMBOL_GPL(blk_rq_cur_bytes);

struct request *elv_next_request(struct request_queue *q)
{
struct request *rq;
int ret;

while ((rq = __elv_next_request(q)) != NULL) {
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;
trace_block_rq_issue(q, 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++;
}

/**
* __end_that_request_first - end I/O on a request
* @req: the request being processed
Expand Down
37 changes: 37 additions & 0 deletions block/blk.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,43 @@ static inline void blk_clear_rq_complete(struct request *rq)
clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
}

/*
* Internal elevator interface
*/
#define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash))

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;
}
}

static inline void elv_activate_rq(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;

if (e->ops->elevator_activate_req_fn)
e->ops->elevator_activate_req_fn(q, rq);
}

static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq)
{
struct elevator_queue *e = q->elevator;

if (e->ops->elevator_deactivate_req_fn)
e->ops->elevator_deactivate_req_fn(q, rq);
}

#ifdef CONFIG_FAIL_IO_TIMEOUT
int blk_should_fake_timeout(struct request_queue *);
ssize_t part_timeout_show(struct device *, struct device_attribute *, char *);
Expand Down
128 changes: 0 additions & 128 deletions block/elevator.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,6 @@ static const int elv_hash_shift = 6;
(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))

DEFINE_TRACE(block_rq_insert);
DEFINE_TRACE(block_rq_issue);
Expand Down Expand Up @@ -310,22 +309,6 @@ void elevator_exit(struct elevator_queue *e)
}
EXPORT_SYMBOL(elevator_exit);

static void elv_activate_rq(struct request_queue *q, struct request *rq)
{
struct elevator_queue *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)
{
struct elevator_queue *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);
Expand Down Expand Up @@ -758,117 +741,6 @@ void elv_add_request(struct request_queue *q, struct request *rq, int where,
}
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) {
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;
trace_block_rq_issue(q, 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++;
}

int elv_queue_empty(struct request_queue *q)
{
struct elevator_queue *e = q->elevator;
Expand Down

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