01_blk_dispatch_queue.patch
Implements generic dispatch queue which can replace all
dispatch queues implemented by each iosched. This reduces
code duplication, eases enforcing semantics over dispatch
queue, and simplifies specific ioscheds.
Signed-off-by: Tejun Heo <[email protected]>
drivers/block/elevator.c | 245 ++++++++++++++++++++++++++++++----------------
drivers/block/ll_rw_blk.c | 26 ++--
include/linux/blkdev.h | 20 ++-
include/linux/elevator.h | 16 +--
4 files changed, 192 insertions(+), 115 deletions(-)
Index: blk-fixes/drivers/block/elevator.c
===================================================================
--- blk-fixes.orig/drivers/block/elevator.c 2005-06-16 13:55:37.000000000 +0900
+++ blk-fixes/drivers/block/elevator.c 2005-06-16 13:55:37.000000000 +0900
@@ -37,18 +37,14 @@
#include <asm/uaccess.h>
-/*
- * XXX HACK XXX Before entering elevator callbacks, we temporailiy
- * turn off REQ_CMD of proxy barrier request so that elevators don't
- * try to account it as a normal one. This ugliness can go away once
- * generic dispatch queue is implemented. - tj
- */
-#define bar_rq_hack_start(q) ((q)->bar_rq && ((q)->bar_rq->flags &= ~REQ_CMD))
-#define bar_rq_hack_end(q) ((q)->bar_rq && ((q)->bar_rq->flags |= REQ_CMD))
-
static DEFINE_SPINLOCK(elv_list_lock);
static LIST_HEAD(elv_list);
+static inline sector_t rq_last_sector(struct request *rq)
+{
+ return rq->sector + rq->nr_sectors;
+}
+
static inline void elv_inc_inflight(request_queue_t *q)
{
q->in_flight++;
@@ -171,6 +167,9 @@ static int elevator_attach(request_queue
INIT_LIST_HEAD(&q->queue_head);
q->last_merge = NULL;
q->elevator = eq;
+ q->last_sector = 0;
+ q->boundary_rq = 0;
+ q->max_back_kb = 0;
if (eq->ops->elevator_init_fn)
ret = eq->ops->elevator_init_fn(q, eq);
@@ -249,6 +248,45 @@ void elevator_exit(elevator_t *e)
kfree(e);
}
+/*
+ * Insert rq into dispatch queue of q. Queue lock must be held on
+ * entry. If sort != 0, rq is sort-inserted; otherwise, rq will be
+ * appended to the dispatch queue. To be used by specific elevators.
+ */
+void elv_dispatch_insert(request_queue_t *q, struct request *rq, int sort)
+{
+ sector_t boundary;
+ unsigned max_back;
+ struct list_head *entry;
+
+ if (!sort) {
+ /* Specific elevator is performing sort. Step away. */
+ q->last_sector = rq_last_sector(rq);
+ q->boundary_rq = rq;
+ list_add_tail(&rq->queuelist, &q->queue_head);
+ return;
+ }
+
+ boundary = q->last_sector;
+ max_back = q->max_back_kb * 2;
+ boundary = boundary > max_back ? boundary - max_back : 0;
+
+ list_for_each_prev(entry, &q->queue_head) {
+ struct request *pos = list_entry_rq(entry);
+
+ if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
+ break;
+ if (rq->sector >= boundary && pos->sector < boundary)
+ continue;
+ if (rq->sector >= pos->sector)
+ break;
+ if (rq->sector < boundary && pos->sector >= boundary)
+ break;
+ }
+
+ list_add(&rq->queuelist, entry);
+}
+
int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
{
elevator_t *e = q->elevator;
@@ -279,13 +317,7 @@ void elv_merge_requests(request_queue_t
e->ops->elevator_merge_req_fn(q, rq, next);
}
-/*
- * For careful internal use by the block layer. Essentially the same as
- * a requeue in that it tells the io scheduler that this request is not
- * active in the driver or hardware anymore, but we don't want the request
- * added back to the scheduler. Function is not exported.
- */
-void elv_deactivate_request(request_queue_t *q, struct request *rq)
+void elv_requeue_request(request_queue_t *q, struct request *rq)
{
elevator_t *e = q->elevator;
@@ -293,75 +325,103 @@ void elv_deactivate_request(request_queu
* it already went through dequeue, we need to decrement the
* in_flight count again
*/
- if (blk_account_rq(rq))
+ if (blk_account_rq(rq)) {
elv_dec_inflight(q);
-
- rq->flags &= ~REQ_STARTED;
-
- if (e->ops->elevator_deactivate_req_fn) {
- bar_rq_hack_start(q);
- e->ops->elevator_deactivate_req_fn(q, rq);
- bar_rq_hack_end(q);
+ if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
+ e->ops->elevator_deactivate_req_fn(q, rq);
}
-}
-
-void elv_requeue_request(request_queue_t *q, struct request *rq)
-{
- elv_deactivate_request(q, rq);
- /*
- * the request is prepped and may have some resources allocated.
- * allowing unprepped requests to pass this one may cause resource
- * deadlock. turn on softbarrier.
- */
- rq->flags |= REQ_SOFTBARRIER;
+ rq->flags &= ~REQ_STARTED;
- /*
- * if iosched has an explicit requeue hook, then use that. otherwise
- * just put the request at the front of the queue
- */
- if (q->elevator->ops->elevator_requeue_req_fn) {
- bar_rq_hack_start(q);
- q->elevator->ops->elevator_requeue_req_fn(q, rq);
- bar_rq_hack_end(q);
- } else
- __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
+ __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
}
void __elv_add_request(request_queue_t *q, struct request *rq, int where,
int plug)
{
- /*
- * barriers implicitly indicate back insertion
- */
- if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER) &&
- where == ELEVATOR_INSERT_SORT)
- where = ELEVATOR_INSERT_BACK;
+ if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
+ /*
+ * barriers implicitly indicate back insertion
+ */
+ if (where == ELEVATOR_INSERT_SORT)
+ where = ELEVATOR_INSERT_BACK;
+
+ /*
+ * this request is scheduling boundary, update last_sector
+ */
+ if (blk_fs_request(rq)) {
+ q->last_sector = rq_last_sector(rq);
+ q->boundary_rq = rq;
+ }
+ }
if (plug)
blk_plug_device(q);
rq->q = q;
- if (!test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
- bar_rq_hack_start(q);
- q->elevator->ops->elevator_add_req_fn(q, rq, where);
- bar_rq_hack_end(q);
-
- if (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);
- }
- } else
+ if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
/*
* if drain is set, store the request "locally". when the drain
* is finished, the requests will be handed ordered to the io
* scheduler
*/
list_add_tail(&rq->queuelist, &q->drain_list);
+ return;
+ }
+
+ switch (where) {
+ case ELEVATOR_INSERT_FRONT:
+ /*
+ * don't let dispatch sorting pass front-inserted requests.
+ */
+ rq->flags |= REQ_SOFTBARRIER;
+
+ list_add(&rq->queuelist, &q->queue_head);
+ break;
+
+ case ELEVATOR_INSERT_BACK:
+ /*
+ * don't let dispatch sorting pass back-inserted requests.
+ */
+ rq->flags |= REQ_SOFTBARRIER;
+
+ while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+ ;
+ 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->flags |= REQ_SORTED;
+ q->elevator->ops->elevator_add_req_fn(q, rq);
+ break;
+
+ default:
+ printk(KERN_ERR "%s: bad insertion point %d\n",
+ __FUNCTION__, where);
+ BUG();
+ }
+
+ if (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(request_queue_t *q, struct request *rq, int where,
@@ -377,10 +437,17 @@ void elv_add_request(request_queue_t *q,
static inline struct request *__elv_next_request(request_queue_t *q)
{
struct request *rq;
- while ((rq = q->elevator->ops->elevator_next_req_fn(q)))
- if (blk_do_ordered(q, &rq))
- break;
- return 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(request_queue_t *q)
@@ -399,6 +466,11 @@ struct request *elv_next_request(request
if (rq == q->last_merge)
q->last_merge = NULL;
+ if (!q->boundary_rq || q->boundary_rq == rq) {
+ q->last_sector = rq_last_sector(rq);
+ q->boundary_rq = NULL;
+ }
+
if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
break;
@@ -409,9 +481,9 @@ struct request *elv_next_request(request
/*
* the request may have been (partially) prepped.
* we need to keep this request in the front to
- * avoid resource deadlock. turn on softbarrier.
+ * avoid resource deadlock. REQ_STARTED will
+ * prevent other fs requests from passing this one.
*/
- rq->flags |= REQ_SOFTBARRIER;
rq = NULL;
break;
} else if (ret == BLKPREP_KILL) {
@@ -434,10 +506,14 @@ struct request *elv_next_request(request
return rq;
}
-void elv_remove_request(request_queue_t *q, struct request *rq)
+void elv_dequeue_request(request_queue_t *q, struct request *rq)
{
elevator_t *e = q->elevator;
+ BUG_ON(list_empty(&rq->queuelist));
+
+ 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
@@ -445,8 +521,11 @@ void elv_remove_request(request_queue_t
* driver has seen (REQ_STARTED set), to avoid false accounting
* for request-request merges
*/
- if (blk_account_rq(rq))
+ if (blk_account_rq(rq)) {
elv_inc_inflight(q);
+ if (blk_sorted_rq(rq) && e->ops->elevator_activate_req_fn)
+ e->ops->elevator_activate_req_fn(q, rq);
+ }
/*
* the main clearing point for q->last_merge is on retrieval of
@@ -457,22 +536,19 @@ void elv_remove_request(request_queue_t
*/
if (rq == q->last_merge)
q->last_merge = NULL;
-
- if (e->ops->elevator_remove_req_fn) {
- bar_rq_hack_start(q);
- e->ops->elevator_remove_req_fn(q, rq);
- bar_rq_hack_end(q);
- }
}
int elv_queue_empty(request_queue_t *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 list_empty(&q->queue_head);
+ return 1;
}
struct request *elv_latter_request(request_queue_t *q, struct request *rq)
@@ -544,11 +620,11 @@ void elv_completed_request(request_queue
/*
* request is released from the driver, io must be done
*/
- if (blk_account_rq(rq))
+ if (blk_account_rq(rq)) {
elv_dec_inflight(q);
-
- if (e->ops->elevator_completed_req_fn)
- e->ops->elevator_completed_req_fn(q, rq);
+ if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
+ e->ops->elevator_completed_req_fn(q, rq);
+ }
}
int elv_register_queue(struct request_queue *q)
@@ -722,11 +798,12 @@ ssize_t elv_iosched_show(request_queue_t
return len;
}
+EXPORT_SYMBOL(elv_dispatch_insert);
EXPORT_SYMBOL(elv_add_request);
EXPORT_SYMBOL(__elv_add_request);
EXPORT_SYMBOL(elv_requeue_request);
EXPORT_SYMBOL(elv_next_request);
-EXPORT_SYMBOL(elv_remove_request);
+EXPORT_SYMBOL(elv_dequeue_request);
EXPORT_SYMBOL(elv_queue_empty);
EXPORT_SYMBOL(elv_completed_request);
EXPORT_SYMBOL(elevator_exit);
Index: blk-fixes/drivers/block/ll_rw_blk.c
===================================================================
--- blk-fixes.orig/drivers/block/ll_rw_blk.c 2005-06-16 13:55:37.000000000 +0900
+++ blk-fixes/drivers/block/ll_rw_blk.c 2005-06-16 13:55:37.000000000 +0900
@@ -519,16 +519,19 @@ void blk_ordered_complete_seq(request_qu
static void pre_flush_end_io(struct request *rq, int error)
{
+ elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
}
static void bar_end_io(struct request *rq, int error)
{
+ elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
}
static void post_flush_end_io(struct request *rq, int error)
{
+ elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
}
@@ -1239,6 +1242,7 @@ EXPORT_SYMBOL(blk_queue_invalidate_tags)
static char *rq_flags[] = {
"REQ_RW",
"REQ_FAILFAST",
+ "REQ_SORTED",
"REQ_SOFTBARRIER",
"REQ_HARDBARRIER",
"REQ_FUA",
@@ -2556,6 +2560,8 @@ static void __blk_put_request(request_qu
if (unlikely(--req->ref_count))
return;
+ elv_completed_request(q, req);
+
req->rq_status = RQ_INACTIVE;
req->rl = NULL;
@@ -2566,8 +2572,6 @@ static void __blk_put_request(request_qu
if (rl) {
int rw = rq_data_dir(req);
- elv_completed_request(q, req);
-
BUG_ON(!list_empty(&req->queuelist));
blk_free_request(q, req);
@@ -2577,18 +2581,12 @@ static void __blk_put_request(request_qu
void blk_put_request(struct request *req)
{
- /*
- * if req->rl isn't set, this request didnt originate from the
- * block layer, so it's safe to just disregard it
- */
- if (req->rl) {
- unsigned long flags;
- request_queue_t *q = req->q;
-
- spin_lock_irqsave(q->queue_lock, flags);
- __blk_put_request(q, req);
- spin_unlock_irqrestore(q->queue_lock, flags);
- }
+ unsigned long flags;
+ request_queue_t *q = req->q;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ __blk_put_request(q, req);
+ spin_unlock_irqrestore(q->queue_lock, flags);
}
EXPORT_SYMBOL(blk_put_request);
Index: blk-fixes/include/linux/blkdev.h
===================================================================
--- blk-fixes.orig/include/linux/blkdev.h 2005-06-16 13:55:37.000000000 +0900
+++ blk-fixes/include/linux/blkdev.h 2005-06-16 13:55:37.000000000 +0900
@@ -203,6 +203,7 @@ struct request {
enum rq_flag_bits {
__REQ_RW, /* not set, read. set, write */
__REQ_FAILFAST, /* no low level driver retries */
+ __REQ_SORTED, /* elevator knows about this request */
__REQ_SOFTBARRIER, /* may not be passed by ioscheduler */
__REQ_HARDBARRIER, /* may not be passed by drive either */
__REQ_FUA, /* forced unit access */
@@ -233,6 +234,7 @@ enum rq_flag_bits {
#define REQ_RW (1 << __REQ_RW)
#define REQ_FAILFAST (1 << __REQ_FAILFAST)
+#define REQ_SORTED (1 << __REQ_SORTED)
#define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)
#define REQ_HARDBARRIER (1 << __REQ_HARDBARRIER)
#define REQ_FUA (1 << __REQ_FUA)
@@ -326,6 +328,13 @@ struct request_queue
prepare_flush_fn *prepare_flush_fn;
/*
+ * Dispatch queue sorting
+ */
+ sector_t last_sector;
+ struct request *boundary_rq;
+ unsigned int max_back_kb;
+
+ /*
* Auto-unplugging state
*/
struct timer_list unplug_timer;
@@ -486,14 +495,14 @@ enum {
#define blk_noretry_request(rq) ((rq)->flags & REQ_FAILFAST)
#define blk_rq_started(rq) ((rq)->flags & REQ_STARTED)
-#define blk_account_rq(rq) \
- (blk_rq_started(rq) && blk_fs_request(rq) && rq != rq->q->bar_rq)
+#define blk_account_rq(rq) (blk_rq_started(rq) && blk_fs_request(rq))
#define blk_pm_suspend_request(rq) ((rq)->flags & REQ_PM_SUSPEND)
#define blk_pm_resume_request(rq) ((rq)->flags & REQ_PM_RESUME)
#define blk_pm_request(rq) \
((rq)->flags & (REQ_PM_SUSPEND | REQ_PM_RESUME))
+#define blk_sorted_rq(rq) ((rq)->flags & REQ_SORTED)
#define blk_barrier_rq(rq) ((rq)->flags & REQ_HARDBARRIER)
#define blk_fua_rq(rq) ((rq)->flags & REQ_FUA)
@@ -648,12 +657,7 @@ extern void end_request(struct request *
static inline void blkdev_dequeue_request(struct request *req)
{
- BUG_ON(list_empty(&req->queuelist));
-
- list_del_init(&req->queuelist);
-
- if (req->rl)
- elv_remove_request(req->q, req);
+ elv_dequeue_request(req->q, req);
}
/*
Index: blk-fixes/include/linux/elevator.h
===================================================================
--- blk-fixes.orig/include/linux/elevator.h 2005-06-16 13:55:37.000000000 +0900
+++ blk-fixes/include/linux/elevator.h 2005-06-16 13:55:37.000000000 +0900
@@ -8,18 +8,17 @@ typedef void (elevator_merge_req_fn) (re
typedef void (elevator_merged_fn) (request_queue_t *, struct request *);
-typedef struct request *(elevator_next_req_fn) (request_queue_t *);
+typedef int (elevator_dispatch_fn) (request_queue_t *, int);
-typedef void (elevator_add_req_fn) (request_queue_t *, struct request *, int);
+typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
typedef int (elevator_queue_empty_fn) (request_queue_t *);
-typedef void (elevator_remove_req_fn) (request_queue_t *, struct request *);
-typedef void (elevator_requeue_req_fn) (request_queue_t *, struct request *);
typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
typedef int (elevator_may_queue_fn) (request_queue_t *, int, struct bio *);
typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, struct bio *, int);
typedef void (elevator_put_req_fn) (request_queue_t *, struct request *);
+typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
typedef int (elevator_init_fn) (request_queue_t *, elevator_t *);
@@ -31,10 +30,9 @@ struct elevator_ops
elevator_merged_fn *elevator_merged_fn;
elevator_merge_req_fn *elevator_merge_req_fn;
- elevator_next_req_fn *elevator_next_req_fn;
+ elevator_dispatch_fn *elevator_dispatch_fn;
elevator_add_req_fn *elevator_add_req_fn;
- elevator_remove_req_fn *elevator_remove_req_fn;
- elevator_requeue_req_fn *elevator_requeue_req_fn;
+ elevator_activate_req_fn *elevator_activate_req_fn;
elevator_deactivate_req_fn *elevator_deactivate_req_fn;
elevator_queue_empty_fn *elevator_queue_empty_fn;
@@ -81,15 +79,15 @@ struct elevator_queue
/*
* block elevator interface
*/
+extern void elv_dispatch_insert(request_queue_t *, struct request *, int);
extern void elv_add_request(request_queue_t *, struct request *, int, int);
extern void __elv_add_request(request_queue_t *, struct request *, int, int);
extern int elv_merge(request_queue_t *, struct request **, struct bio *);
extern void elv_merge_requests(request_queue_t *, struct request *,
struct request *);
extern void elv_merged_request(request_queue_t *, struct request *);
-extern void elv_remove_request(request_queue_t *, struct request *);
+extern void elv_dequeue_request(request_queue_t *, struct request *);
extern void elv_requeue_request(request_queue_t *, struct request *);
-extern void elv_deactivate_request(request_queue_t *, struct request *);
extern int elv_queue_empty(request_queue_t *);
extern struct request *elv_next_request(struct request_queue *q);
extern struct request *elv_former_request(request_queue_t *, struct request *);
-
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