1 files changed, 207 insertions, 138 deletions

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
index 98f0126a2deb..55621d5c5774 100644
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -34,6 +34,7 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/compiler.h>
+#include <linux/delay.h>
 
 #include <asm/uaccess.h>
 
@@ -83,21 +84,11 @@ inline int elv_try_merge(struct request *__rq, struct bio *bio)
 }
 EXPORT_SYMBOL(elv_try_merge);
 
-inline int elv_try_last_merge(request_queue_t *q, struct bio *bio)
-{
-        if (q->last_merge)
-                return elv_try_merge(q->last_merge, bio);
-
-        return ELEVATOR_NO_MERGE;
-}
-EXPORT_SYMBOL(elv_try_last_merge);
-
 static struct elevator_type *elevator_find(const char *name)
 {
         struct elevator_type *e = NULL;
         struct list_head *entry;
 
-        spin_lock_irq(&elv_list_lock);
         list_for_each(entry, &elv_list) {
                 struct elevator_type *__e;
 
@@ -108,7 +99,6 @@ static struct elevator_type *elevator_find(const char *name)
                         break;
                 }
         }
-        spin_unlock_irq(&elv_list_lock);
 
         return e;
 }
@@ -120,12 +110,15 @@ static void elevator_put(struct elevator_type *e)
 
 static struct elevator_type *elevator_get(const char *name)
 {
-        struct elevator_type *e = elevator_find(name);
+        struct elevator_type *e;
 
-        if (!e)
-                return NULL;
-        if (!try_module_get(e->elevator_owner))
-                return NULL;
+        spin_lock_irq(&elv_list_lock);
+
+        e = elevator_find(name);
+        if (e && !try_module_get(e->elevator_owner))
+                e = NULL;
+
+        spin_unlock_irq(&elv_list_lock);
 
         return e;
 }
@@ -139,8 +132,6 @@ static int elevator_attach(request_queue_t *q, struct elevator_type *e,
         eq->ops = &e->ops;
         eq->elevator_type = e;
 
-        INIT_LIST_HEAD(&q->queue_head);
-        q->last_merge = NULL;
         q->elevator = eq;
 
         if (eq->ops->elevator_init_fn)
@@ -153,11 +144,15 @@ static char chosen_elevator[16];
 
 static void elevator_setup_default(void)
 {
+        struct elevator_type *e;
+
         /*
          * check if default is set and exists
          */
-        if (chosen_elevator[0] && elevator_find(chosen_elevator))
+        if (chosen_elevator[0] && (e = elevator_get(chosen_elevator))) {
+                elevator_put(e);
                 return;
+        }
 
 #if defined(CONFIG_IOSCHED_AS)
         strcpy(chosen_elevator, "anticipatory");
@@ -186,6 +181,11 @@ int elevator_init(request_queue_t *q, char *name)
         struct elevator_queue *eq;
         int ret = 0;
 
+        INIT_LIST_HEAD(&q->queue_head);
+        q->last_merge = NULL;
+        q->end_sector = 0;
+        q->boundary_rq = NULL;
+
         elevator_setup_default();
 
         if (!name)
@@ -220,9 +220,52 @@ 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_sort(request_queue_t *q, struct request *rq)
+{
+        sector_t boundary;
+        struct list_head *entry;
+
+        if (q->last_merge == rq)
+                q->last_merge = NULL;
+
+        boundary = q->end_sector;
+
+        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) {
+                        if (pos->sector < boundary)
+                                continue;
+                } else {
+                        if (pos->sector >= boundary)
+                                break;
+                }
+                if (rq->sector >= pos->sector)
+                        break;
+        }
+
+        list_add(&rq->queuelist, entry);
+}
+
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
         elevator_t *e = q->elevator;
+        int ret;
+
+        if (q->last_merge) {
+                ret = elv_try_merge(q->last_merge, bio);
+                if (ret != ELEVATOR_NO_MERGE) {
+                        *req = q->last_merge;
+                        return ret;
+                }
+        }
 
         if (e->ops->elevator_merge_fn)
                 return e->ops->elevator_merge_fn(q, req, bio);
@@ -236,6 +279,8 @@ void elv_merged_request(request_queue_t *q, struct request *rq)
 
         if (e->ops->elevator_merged_fn)
                 e->ops->elevator_merged_fn(q, rq);
+
+        q->last_merge = rq;
 }
 
 void elv_merge_requests(request_queue_t *q, struct request *rq,
@@ -243,20 +288,13 @@ void elv_merge_requests(request_queue_t *q, struct request *rq,
 {
         elevator_t *e = q->elevator;
 
-        if (q->last_merge == next)
-                q->last_merge = NULL;
-
         if (e->ops->elevator_merge_req_fn)
                 e->ops->elevator_merge_req_fn(q, rq, next);
+
+        q->last_merge = rq;
 }
 
-/*
- * 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;
 
@@ -264,19 +302,14 @@ void elv_deactivate_request(request_queue_t *q, struct request *rq)
          * it already went through dequeue, we need to decrement the
          * in_flight count again
          */
-        if (blk_account_rq(rq))
+        if (blk_account_rq(rq)) {
                 q->in_flight--;
+                if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
+                        e->ops->elevator_deactivate_req_fn(q, rq);
+        }
 
         rq->flags &= ~REQ_STARTED;
 
-        if (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);
-
         /*
          * if this is the flush, requeue the original instead and drop the flush
          */
@@ -285,31 +318,27 @@ void elv_requeue_request(request_queue_t *q, struct request *rq)
                 rq = rq->end_io_data;
         }
 
-        /*
-         * 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;
-
-        /*
-         * 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)
-                q->elevator->ops->elevator_requeue_req_fn(q, rq);
-        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)
+        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 end_sector
+                 */
+                if (blk_fs_request(rq)) {
+                        q->end_sector = rq_end_sector(rq);
+                        q->boundary_rq = rq;
+                }
+        } else if (!(rq->flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
                 where = ELEVATOR_INSERT_BACK;
 
         if (plug)
@@ -317,23 +346,54 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
 
         rq->q = q;
 
-        if (!test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
-                q->elevator->ops->elevator_add_req_fn(q, rq, where);
+        switch (where) {
+        case ELEVATOR_INSERT_FRONT:
+                rq->flags |= REQ_SOFTBARRIER;
 
-                if (blk_queue_plugged(q)) {
-                        int nrq = q->rq.count[READ] + q->rq.count[WRITE]
-                                  - q->in_flight;
+                list_add(&rq->queuelist, &q->queue_head);
+                break;
 
-                        if (nrq >= q->unplug_thresh)
-                                __generic_unplug_device(q);
-                }
-        } else
+        case ELEVATOR_INSERT_BACK:
+                rq->flags |= REQ_SOFTBARRIER;
+
+                while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+                        ;
+                list_add_tail(&rq->queuelist, &q->queue_head);
                 /*
-                 * if drain is set, store the request "locally". when the drain
-                 * is finished, the requests will be handed ordered to the io
-                 * scheduler
+                 * 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.
                  */
-                list_add_tail(&rq->queuelist, &q->drain_list);
+                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);
+                if (q->last_merge == NULL && rq_mergeable(rq))
+                        q->last_merge = 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,
@@ -348,13 +408,19 @@ void elv_add_request(request_queue_t *q, struct request *rq, int where,
 
 static inline struct request *__elv_next_request(request_queue_t *q)
 {
-        struct request *rq = q->elevator->ops->elevator_next_req_fn(q);
+        struct request *rq;
+
+        if (unlikely(list_empty(&q->queue_head) &&
+                     !q->elevator->ops->elevator_dispatch_fn(q, 0)))
+                return NULL;
+
+        rq = list_entry_rq(q->queue_head.next);
 
         /*
          * if this is a barrier write and the device has to issue a
          * flush sequence to support it, check how far we are
          */
-        if (rq && blk_fs_request(rq) && blk_barrier_rq(rq)) {
+        if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
                 BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
 
                 if (q->ordered == QUEUE_ORDERED_FLUSH &&
@@ -371,15 +437,30 @@ struct request *elv_next_request(request_queue_t *q)
         int ret;
 
         while ((rq = __elv_next_request(q)) != NULL) {
-                /*
-                 * 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->flags |= REQ_STARTED;
+                if (!(rq->flags & REQ_STARTED)) {
+                        elevator_t *e = q->elevator;
 
-                if (rq == q->last_merge)
-                        q->last_merge = NULL;
+                        /*
+                         * This is the first time the device driver
+                         * sees this request (possibly after
+                         * requeueing).  Notify IO scheduler.
+                         */
+                        if (blk_sorted_rq(rq) &&
+                            e->ops->elevator_activate_req_fn)
+                                e->ops->elevator_activate_req_fn(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->flags |= REQ_STARTED;
+                }
+
+                if (!q->boundary_rq || q->boundary_rq == rq) {
+                        q->end_sector = rq_end_sector(rq);
+                        q->boundary_rq = NULL;
+                }
 
                 if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
                         break;
@@ -391,9 +472,9 @@ struct request *elv_next_request(request_queue_t *q)
                         /*
                          * 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) {
@@ -416,42 +497,32 @@ struct request *elv_next_request(request_queue_t *q)
         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
-         * the driver side. note that we only account requests that the
-         * driver has seen (REQ_STARTED set), to avoid false accounting
-         * for request-request merges
+         * the driver side.
          */
         if (blk_account_rq(rq))
                 q->in_flight++;
-
-        /*
-         * the main clearing point for q->last_merge is on retrieval of
-         * request by driver (it calls elv_next_request()), but it _can_
-         * also happen here if a request is added to the queue but later
-         * deleted without ever being given to driver (merged with another
-         * request).
-         */
-        if (rq == q->last_merge)
-                q->last_merge = NULL;
-
-        if (e->ops->elevator_remove_req_fn)
-                e->ops->elevator_remove_req_fn(q, rq);
 }
 
 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)
@@ -487,7 +558,7 @@ struct request *elv_former_request(request_queue_t *q, struct request *rq)
 }
 
 int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
-                    int gfp_mask)
+                    gfp_t gfp_mask)
 {
         elevator_t *e = q->elevator;
 
@@ -523,11 +594,11 @@ void elv_completed_request(request_queue_t *q, struct request *rq)
         /*
          * request is released from the driver, io must be done
          */
-        if (blk_account_rq(rq))
+        if (blk_account_rq(rq)) {
                 q->in_flight--;
-
-        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)
@@ -555,10 +626,9 @@ void elv_unregister_queue(struct request_queue *q)
 
 int elv_register(struct elevator_type *e)
 {
+        spin_lock_irq(&elv_list_lock);
         if (elevator_find(e->elevator_name))
                 BUG();
-
-        spin_lock_irq(&elv_list_lock);
         list_add_tail(&e->list, &elv_list);
         spin_unlock_irq(&elv_list_lock);
 
@@ -582,25 +652,36 @@ 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. we also do an intermediate
- * switch to noop to ensure safety with stack-allocated requests, since they
- * don't originate from the block layer allocator. noop is safe here, because
- * it never needs to touch the elevator itself for completion events. DRAIN
- * flags will make sure we don't touch it for additions either.
+ * one, if the new one fails init for some reason.
  */
 static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 {
-        elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
-        struct elevator_type *noop_elevator = NULL;
-        elevator_t *old_elevator;
+        elevator_t *old_elevator, *e;
 
+        /*
+         * Allocate new elevator
+         */
+        e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
         if (!e)
                 goto error;
 
         /*
-         * first step, drain requests from the block freelist
+         * Turn on BYPASS and drain all requests w/ elevator private data
          */
-        blk_wait_queue_drained(q, 0);
+        spin_lock_irq(q->queue_lock);
+
+        set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+
+        while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+                ;
+
+        while (q->rq.elvpriv) {
+                spin_unlock_irq(q->queue_lock);
+                msleep(10);
+                spin_lock_irq(q->queue_lock);
+        }
+
+        spin_unlock_irq(q->queue_lock);
 
         /*
          * unregister old elevator data
@@ -609,18 +690,6 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
         old_elevator = q->elevator;
 
         /*
-         * next step, switch to noop since it uses no private rq structures
-         * and doesn't allocate any memory for anything. then wait for any
-         * non-fs requests in-flight
-         */
-        noop_elevator = elevator_get("noop");
-        spin_lock_irq(q->queue_lock);
-        elevator_attach(q, noop_elevator, e);
-        spin_unlock_irq(q->queue_lock);
-
-        blk_wait_queue_drained(q, 1);
-
-        /*
          * attach and start new elevator
          */
         if (elevator_attach(q, new_e, e))
@@ -630,11 +699,10 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
                 goto fail_register;
 
         /*
-         * finally exit old elevator and start queue again
+         * finally exit old elevator and turn off BYPASS.
          */
         elevator_exit(old_elevator);
-        blk_finish_queue_drain(q);
-        elevator_put(noop_elevator);
+        clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
         return;
 
 fail_register:
@@ -643,13 +711,13 @@ fail_register:
          * one again (along with re-adding the sysfs dir)
          */
         elevator_exit(e);
+        e = NULL;
 fail:
         q->elevator = old_elevator;
         elv_register_queue(q);
-        blk_finish_queue_drain(q);
+        clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+        kfree(e);
 error:
-        if (noop_elevator)
-                elevator_put(noop_elevator);
         elevator_put(new_e);
         printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
 }
@@ -701,11 +769,12 @@ ssize_t elv_iosched_show(request_queue_t *q, char *name)
         return len;
 }
 
+EXPORT_SYMBOL(elv_dispatch_sort);
 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);