1 files changed, 105 insertions, 101 deletions

diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 60e64091de1b..692a5fced76e 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -276,6 +276,7 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
         rq->errors = 0;
         rq->rq_status = RQ_ACTIVE;
         rq->bio = rq->biotail = NULL;
+        rq->ioprio = 0;
         rq->buffer = NULL;
         rq->ref_count = 1;
         rq->q = q;
@@ -1442,11 +1443,7 @@ void __generic_unplug_device(request_queue_t *q)
         if (!blk_remove_plug(q))
                 return;
 
-        /*
-         * was plugged, fire request_fn if queue has stuff to do
-         */
-        if (elv_next_request(q))
-                q->request_fn(q);
+        q->request_fn(q);
 }
 EXPORT_SYMBOL(__generic_unplug_device);
 
@@ -1776,8 +1773,8 @@ static inline void blk_free_request(request_queue_t *q, struct request *rq)
         mempool_free(rq, q->rq.rq_pool);
 }
 
-static inline struct request *blk_alloc_request(request_queue_t *q, int rw,
-                                                int gfp_mask)
+static inline struct request *
+blk_alloc_request(request_queue_t *q, int rw, struct bio *bio, int gfp_mask)
 {
         struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 
@@ -1790,7 +1787,7 @@ static inline struct request *blk_alloc_request(request_queue_t *q, int rw,
          */
         rq->flags = rw;
 
-        if (!elv_set_request(q, rq, gfp_mask))
+        if (!elv_set_request(q, rq, bio, gfp_mask))
                 return rq;
 
         mempool_free(rq, q->rq.rq_pool);
@@ -1870,18 +1867,20 @@ static void freed_request(request_queue_t *q, int rw)
 
 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
 /*
- * Get a free request, queue_lock must not be held
+ * Get a free request, queue_lock must be held.
+ * Returns NULL on failure, with queue_lock held.
+ * Returns !NULL on success, with queue_lock *not held*.
  */
-static struct request *get_request(request_queue_t *q, int rw, int gfp_mask)
+static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
+                                   int gfp_mask)
 {
         struct request *rq = NULL;
         struct request_list *rl = &q->rq;
-        struct io_context *ioc = get_io_context(gfp_mask);
+        struct io_context *ioc = current_io_context(GFP_ATOMIC);
 
         if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)))
                 goto out;
 
-        spin_lock_irq(q->queue_lock);
         if (rl->count[rw]+1 >= q->nr_requests) {
                 /*
                  * The queue will fill after this allocation, so set it as
@@ -1895,7 +1894,7 @@ static struct request *get_request(request_queue_t *q, int rw, int gfp_mask)
                 }
         }
 
-        switch (elv_may_queue(q, rw)) {
+        switch (elv_may_queue(q, rw, bio)) {
                 case ELV_MQUEUE_NO:
                         goto rq_starved;
                 case ELV_MQUEUE_MAY:
@@ -1909,18 +1908,25 @@ static struct request *get_request(request_queue_t *q, int rw, int gfp_mask)
                  * The queue is full and the allocating process is not a
                  * "batcher", and not exempted by the IO scheduler
                  */
-                spin_unlock_irq(q->queue_lock);
                 goto out;
         }
 
 get_rq:
+        /*
+         * Only allow batching queuers to allocate up to 50% over the defined
+         * limit of requests, otherwise we could have thousands of requests
+         * allocated with any setting of ->nr_requests
+         */
+        if (rl->count[rw] >= (3 * q->nr_requests / 2))
+                goto out;
+
         rl->count[rw]++;
         rl->starved[rw] = 0;
         if (rl->count[rw] >= queue_congestion_on_threshold(q))
                 set_queue_congested(q, rw);
         spin_unlock_irq(q->queue_lock);
 
-        rq = blk_alloc_request(q, rw, gfp_mask);
+        rq = blk_alloc_request(q, rw, bio, gfp_mask);
         if (!rq) {
                 /*
                  * Allocation failed presumably due to memory. Undo anything
@@ -1943,7 +1949,6 @@ rq_starved:
                 if (unlikely(rl->count[rw] == 0))
                         rl->starved[rw] = 1;
 
-                spin_unlock_irq(q->queue_lock);
                 goto out;
         }
 
@@ -1953,31 +1958,35 @@ rq_starved:
         rq_init(q, rq);
         rq->rl = rl;
 out:
-        put_io_context(ioc);
         return rq;
 }
 
 /*
  * No available requests for this queue, unplug the device and wait for some
  * requests to become available.
+ *
+ * Called with q->queue_lock held, and returns with it unlocked.
  */
-static struct request *get_request_wait(request_queue_t *q, int rw)
+static struct request *get_request_wait(request_queue_t *q, int rw,
+                                        struct bio *bio)
 {
-        DEFINE_WAIT(wait);
         struct request *rq;
 
-        do {
+        rq = get_request(q, rw, bio, GFP_NOIO);
+        while (!rq) {
+                DEFINE_WAIT(wait);
                 struct request_list *rl = &q->rq;
 
                 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
                                 TASK_UNINTERRUPTIBLE);
 
-                rq = get_request(q, rw, GFP_NOIO);
+                rq = get_request(q, rw, bio, GFP_NOIO);
 
                 if (!rq) {
                         struct io_context *ioc;
 
-                        generic_unplug_device(q);
+                        __generic_unplug_device(q);
+                        spin_unlock_irq(q->queue_lock);
                         io_schedule();
 
                         /*
@@ -1986,12 +1995,13 @@ static struct request *get_request_wait(request_queue_t *q, int rw)
                          * up to a big batch of them for a small period time.
                          * See ioc_batching, ioc_set_batching
                          */
-                        ioc = get_io_context(GFP_NOIO);
+                        ioc = current_io_context(GFP_NOIO);
                         ioc_set_batching(q, ioc);
-                        put_io_context(ioc);
+
+                        spin_lock_irq(q->queue_lock);
                 }
                 finish_wait(&rl->wait[rw], &wait);
-        } while (!rq);
+        }
 
         return rq;
 }
@@ -2002,14 +2012,18 @@ struct request *blk_get_request(request_queue_t *q, int rw, int gfp_mask)
 
         BUG_ON(rw != READ && rw != WRITE);
 
-        if (gfp_mask & __GFP_WAIT)
-                rq = get_request_wait(q, rw);
-        else
-                rq = get_request(q, rw, gfp_mask);
+        spin_lock_irq(q->queue_lock);
+        if (gfp_mask & __GFP_WAIT) {
+                rq = get_request_wait(q, rw, NULL);
+        } else {
+                rq = get_request(q, rw, NULL, gfp_mask);
+                if (!rq)
+                        spin_unlock_irq(q->queue_lock);
+        }
+        /* q->queue_lock is unlocked at this point */
 
         return rq;
 }
-
 EXPORT_SYMBOL(blk_get_request);
 
 /**
@@ -2333,7 +2347,6 @@ static void __blk_put_request(request_queue_t *q, struct request *req)
                 return;
 
         req->rq_status = RQ_INACTIVE;
-        req->q = NULL;
         req->rl = NULL;
 
         /*
@@ -2462,6 +2475,8 @@ static int attempt_merge(request_queue_t *q, struct request *req,
                 req->rq_disk->in_flight--;
         }
 
+        req->ioprio = ioprio_best(req->ioprio, next->ioprio);
+
         __blk_put_request(q, next);
         return 1;
 }
@@ -2512,13 +2527,15 @@ EXPORT_SYMBOL(blk_attempt_remerge);
 
 static int __make_request(request_queue_t *q, struct bio *bio)
 {
-        struct request *req, *freereq = NULL;
+        struct request *req;
         int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
+        unsigned short prio;
         sector_t sector;
 
         sector = bio->bi_sector;
         nr_sectors = bio_sectors(bio);
         cur_nr_sectors = bio_cur_sectors(bio);
+        prio = bio_prio(bio);
 
         rw = bio_data_dir(bio);
         sync = bio_sync(bio);
@@ -2538,14 +2555,9 @@ static int __make_request(request_queue_t *q, struct bio *bio)
                 goto end_io;
         }
 
-again:
         spin_lock_irq(q->queue_lock);
 
-        if (elv_queue_empty(q)) {
-                blk_plug_device(q);
-                goto get_rq;
-        }
-        if (barrier)
+        if (unlikely(barrier) || elv_queue_empty(q))
                 goto get_rq;
 
         el_ret = elv_merge(q, &req, bio);
@@ -2559,6 +2571,7 @@ again:
                         req->biotail->bi_next = bio;
                         req->biotail = bio;
                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
+                        req->ioprio = ioprio_best(req->ioprio, prio);
                         drive_stat_acct(req, nr_sectors, 0);
                         if (!attempt_back_merge(q, req))
                                 elv_merged_request(q, req);
@@ -2583,45 +2596,30 @@ again:
                         req->hard_cur_sectors = cur_nr_sectors;
                         req->sector = req->hard_sector = sector;
                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
+                        req->ioprio = ioprio_best(req->ioprio, prio);
                         drive_stat_acct(req, nr_sectors, 0);
                         if (!attempt_front_merge(q, req))
                                 elv_merged_request(q, req);
                         goto out;
 
-                /*
-                 * elevator says don't/can't merge. get new request
-                 */
-                case ELEVATOR_NO_MERGE:
-                        break;
-
+                /* ELV_NO_MERGE: elevator says don't/can't merge. */
                 default:
-                        printk("elevator returned crap (%d)\n", el_ret);
-                        BUG();
+                        ;
         }
 
+get_rq:
         /*
-         * Grab a free request from the freelist - if that is empty, check
-         * if we are doing read ahead and abort instead of blocking for
-         * a free slot.
+         * Grab a free request. This is might sleep but can not fail.
+         * Returns with the queue unlocked.
+         */
+        req = get_request_wait(q, rw, bio);
+
+        /*
+         * After dropping the lock and possibly sleeping here, our request
+         * may now be mergeable after it had proven unmergeable (above).
+         * We don't worry about that case for efficiency. It won't happen
+         * often, and the elevators are able to handle it.
          */
-get_rq:
-        if (freereq) {
-                req = freereq;
-                freereq = NULL;
-        } else {
-                spin_unlock_irq(q->queue_lock);
-                if ((freereq = get_request(q, rw, GFP_ATOMIC)) == NULL) {
-                        /*
-                         * READA bit set
-                         */
-                        err = -EWOULDBLOCK;
-                        if (bio_rw_ahead(bio))
-                                goto end_io;
-        
-                        freereq = get_request_wait(q, rw);
-                }
-                goto again;
-        }
 
         req->flags |= REQ_CMD;
 
@@ -2646,13 +2644,15 @@ get_rq:
         req->buffer = bio_data(bio);    /* see ->buffer comment above */
         req->waiting = NULL;
         req->bio = req->biotail = bio;
+        req->ioprio = prio;
         req->rq_disk = bio->bi_bdev->bd_disk;
         req->start_time = jiffies;
 
+        spin_lock_irq(q->queue_lock);
+        if (elv_queue_empty(q))
+                blk_plug_device(q);
         add_request(q, req);
 out:
-        if (freereq)
-                __blk_put_request(q, freereq);
         if (sync)
                 __generic_unplug_device(q);
 
@@ -2674,7 +2674,7 @@ static inline void blk_partition_remap(struct bio *bio)
         if (bdev != bdev->bd_contains) {
                 struct hd_struct *p = bdev->bd_part;
 
-                switch (bio->bi_rw) {
+                switch (bio_data_dir(bio)) {
                 case READ:
                         p->read_sectors += bio_sectors(bio);
                         p->reads++;
@@ -2693,6 +2693,7 @@ void blk_finish_queue_drain(request_queue_t *q)
 {
         struct request_list *rl = &q->rq;
         struct request *rq;
+        int requeued = 0;
 
         spin_lock_irq(q->queue_lock);
         clear_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
@@ -2701,9 +2702,13 @@ void blk_finish_queue_drain(request_queue_t *q)
                 rq = list_entry_rq(q->drain_list.next);
 
                 list_del_init(&rq->queuelist);
-                __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
+                elv_requeue_request(q, rq);
+                requeued++;
         }
 
+        if (requeued)
+                q->request_fn(q);
+
         spin_unlock_irq(q->queue_lock);
 
         wake_up(&rl->wait[0]);
@@ -2900,7 +2905,7 @@ void submit_bio(int rw, struct bio *bio)
 
         BIO_BUG_ON(!bio->bi_size);
         BIO_BUG_ON(!bio->bi_io_vec);
-        bio->bi_rw = rw;
+        bio->bi_rw |= rw;
         if (rw & WRITE)
                 mod_page_state(pgpgout, count);
         else
@@ -3257,8 +3262,11 @@ void exit_io_context(void)
         struct io_context *ioc;
 
         local_irq_save(flags);
+        task_lock(current);
         ioc = current->io_context;
         current->io_context = NULL;
+        ioc->task = NULL;
+        task_unlock(current);
         local_irq_restore(flags);
 
         if (ioc->aic && ioc->aic->exit)
@@ -3271,53 +3279,49 @@ void exit_io_context(void)
 
 /*
  * If the current task has no IO context then create one and initialise it.
- * If it does have a context, take a ref on it.
+ * Otherwise, return its existing IO context.
  *
- * This is always called in the context of the task which submitted the I/O.
- * But weird things happen, so we disable local interrupts to ensure exclusive
- * access to *current.
+ * This returned IO context doesn't have a specifically elevated refcount,
+ * but since the current task itself holds a reference, the context can be
+ * used in general code, so long as it stays within `current` context.
  */
-struct io_context *get_io_context(int gfp_flags)
+struct io_context *current_io_context(int gfp_flags)
 {
         struct task_struct *tsk = current;
-        unsigned long flags;
         struct io_context *ret;
 
-        local_irq_save(flags);
         ret = tsk->io_context;
-        if (ret)
-                goto out;
-
-        local_irq_restore(flags);
+        if (likely(ret))
+                return ret;
 
         ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
         if (ret) {
                 atomic_set(&ret->refcount, 1);
-                ret->pid = tsk->pid;
+                ret->task = current;
+                ret->set_ioprio = NULL;
                 ret->last_waited = jiffies; /* doesn't matter... */
                 ret->nr_batch_requests = 0; /* because this is 0 */
                 ret->aic = NULL;
                 ret->cic = NULL;
-                spin_lock_init(&ret->lock);
-
-                local_irq_save(flags);
+                tsk->io_context = ret;
+        }
 
-                /*
-                 * very unlikely, someone raced with us in setting up the task
-                 * io context. free new context and just grab a reference.
-                 */
-                if (!tsk->io_context)
-                        tsk->io_context = ret;
-                else {
-                        kmem_cache_free(iocontext_cachep, ret);
-                        ret = tsk->io_context;
-                }
+        return ret;
+}
+EXPORT_SYMBOL(current_io_context);
 
-out:
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ */
+struct io_context *get_io_context(int gfp_flags)
+{
+        struct io_context *ret;
+        ret = current_io_context(gfp_flags);
+        if (likely(ret))
                 atomic_inc(&ret->refcount);
-                local_irq_restore(flags);
-        }
-
         return ret;
 }
 EXPORT_SYMBOL(get_io_context);