diff options
author | Tejun Heo <htejun@gmail.com> | 2005-10-28 08:29:39 +0200 |
---|---|---|
committer | Jens Axboe <axboe@nelson.home.kernel.dk> | 2005-10-28 08:48:12 +0200 |
commit | cb98fc8bb9c141009e2bda99c0db39d387e142cf (patch) | |
tree | 8957f8a79f39c3e6633a0dbb165ced8b530aca0c /drivers/block/ll_rw_blk.c | |
parent | [BLOCK] kill generic max_back_kb handling (diff) | |
download | linux-cb98fc8bb9c141009e2bda99c0db39d387e142cf.tar.xz linux-cb98fc8bb9c141009e2bda99c0db39d387e142cf.zip |
[BLOCK] Reimplement elevator switch
This patch reimplements elevator switch. This patch assumes generic
dispatch queue patchset is applied.
* Each request is tagged with REQ_ELVPRIV flag if it has its elevator
private data set.
* Requests which doesn't have REQ_ELVPRIV flag set never enter
iosched. They are always directly back inserted to dispatch queue.
Of course, elevator_put_req_fn is called only for requests which
have its REQ_ELVPRIV set.
* Request queue maintains the current number of requests which have
its elevator data set (elevator_set_req_fn called) in
q->rq->elvpriv.
* If a request queue has QUEUE_FLAG_BYPASS set, elevator private data
is not allocated for new requests.
To switch to another iosched, we set QUEUE_FLAG_BYPASS and wait until
elvpriv goes to zero; then, we attach the new iosched and clears
QUEUE_FLAG_BYPASS. New implementation is much simpler and main code
paths are less cluttered, IMHO.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
Diffstat (limited to 'drivers/block/ll_rw_blk.c')
-rw-r--r-- | drivers/block/ll_rw_blk.c | 142 |
1 files changed, 27 insertions, 115 deletions
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c index d2a66fd309c3..f7c9931cb380 100644 --- a/drivers/block/ll_rw_blk.c +++ b/drivers/block/ll_rw_blk.c @@ -263,8 +263,6 @@ void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn) blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH); blk_queue_activity_fn(q, NULL, NULL); - - INIT_LIST_HEAD(&q->drain_list); } EXPORT_SYMBOL(blk_queue_make_request); @@ -1050,6 +1048,7 @@ static char *rq_flags[] = { "REQ_STARTED", "REQ_DONTPREP", "REQ_QUEUED", + "REQ_ELVPRIV", "REQ_PC", "REQ_BLOCK_PC", "REQ_SENSE", @@ -1640,9 +1639,9 @@ static int blk_init_free_list(request_queue_t *q) rl->count[READ] = rl->count[WRITE] = 0; rl->starved[READ] = rl->starved[WRITE] = 0; + rl->elvpriv = 0; init_waitqueue_head(&rl->wait[READ]); init_waitqueue_head(&rl->wait[WRITE]); - init_waitqueue_head(&rl->drain); rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, request_cachep, q->node); @@ -1785,12 +1784,14 @@ EXPORT_SYMBOL(blk_get_queue); static inline void blk_free_request(request_queue_t *q, struct request *rq) { - elv_put_request(q, rq); + if (rq->flags & REQ_ELVPRIV) + elv_put_request(q, rq); mempool_free(rq, q->rq.rq_pool); } static inline struct request * -blk_alloc_request(request_queue_t *q, int rw, struct bio *bio, int gfp_mask) +blk_alloc_request(request_queue_t *q, int rw, struct bio *bio, + int priv, int gfp_mask) { struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask); @@ -1803,11 +1804,15 @@ blk_alloc_request(request_queue_t *q, int rw, struct bio *bio, int gfp_mask) */ rq->flags = rw; - if (!elv_set_request(q, rq, bio, gfp_mask)) - return rq; + if (priv) { + if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) { + mempool_free(rq, q->rq.rq_pool); + return NULL; + } + rq->flags |= REQ_ELVPRIV; + } - mempool_free(rq, q->rq.rq_pool); - return NULL; + return rq; } /* @@ -1863,22 +1868,18 @@ static void __freed_request(request_queue_t *q, int rw) * A request has just been released. Account for it, update the full and * congestion status, wake up any waiters. Called under q->queue_lock. */ -static void freed_request(request_queue_t *q, int rw) +static void freed_request(request_queue_t *q, int rw, int priv) { struct request_list *rl = &q->rq; rl->count[rw]--; + if (priv) + rl->elvpriv--; __freed_request(q, rw); if (unlikely(rl->starved[rw ^ 1])) __freed_request(q, rw ^ 1); - - if (!rl->count[READ] && !rl->count[WRITE]) { - smp_mb(); - if (unlikely(waitqueue_active(&rl->drain))) - wake_up(&rl->drain); - } } #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist) @@ -1893,9 +1894,7 @@ static struct request *get_request(request_queue_t *q, int rw, struct bio *bio, struct request *rq = NULL; struct request_list *rl = &q->rq; struct io_context *ioc = current_io_context(GFP_ATOMIC); - - if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) - goto out; + int priv; if (rl->count[rw]+1 >= q->nr_requests) { /* @@ -1940,9 +1939,14 @@ get_rq: rl->starved[rw] = 0; if (rl->count[rw] >= queue_congestion_on_threshold(q)) set_queue_congested(q, rw); + + priv = !test_bit(QUEUE_FLAG_BYPASS, &q->queue_flags); + if (priv) + rl->elvpriv++; + spin_unlock_irq(q->queue_lock); - rq = blk_alloc_request(q, rw, bio, gfp_mask); + rq = blk_alloc_request(q, rw, bio, priv, gfp_mask); if (!rq) { /* * Allocation failed presumably due to memory. Undo anything @@ -1952,7 +1956,7 @@ get_rq: * wait queue, but this is pretty rare. */ spin_lock_irq(q->queue_lock); - freed_request(q, rw); + freed_request(q, rw, priv); /* * in the very unlikely event that allocation failed and no @@ -2470,11 +2474,12 @@ static void __blk_put_request(request_queue_t *q, struct request *req) */ if (rl) { int rw = rq_data_dir(req); + int priv = req->flags & REQ_ELVPRIV; BUG_ON(!list_empty(&req->queuelist)); blk_free_request(q, req); - freed_request(q, rw); + freed_request(q, rw, priv); } } @@ -2802,97 +2807,6 @@ static inline void blk_partition_remap(struct bio *bio) } } -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); - - while (!list_empty(&q->drain_list)) { - rq = list_entry_rq(q->drain_list.next); - - list_del_init(&rq->queuelist); - elv_requeue_request(q, rq); - requeued++; - } - - if (requeued) - q->request_fn(q); - - spin_unlock_irq(q->queue_lock); - - wake_up(&rl->wait[0]); - wake_up(&rl->wait[1]); - wake_up(&rl->drain); -} - -static int wait_drain(request_queue_t *q, struct request_list *rl, int dispatch) -{ - int wait = rl->count[READ] + rl->count[WRITE]; - - if (dispatch) - wait += !list_empty(&q->queue_head); - - return wait; -} - -/* - * We rely on the fact that only requests allocated through blk_alloc_request() - * have io scheduler private data structures associated with them. Any other - * type of request (allocated on stack or through kmalloc()) should not go - * to the io scheduler core, but be attached to the queue head instead. - */ -void blk_wait_queue_drained(request_queue_t *q, int wait_dispatch) -{ - struct request_list *rl = &q->rq; - DEFINE_WAIT(wait); - - spin_lock_irq(q->queue_lock); - set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags); - - while (wait_drain(q, rl, wait_dispatch)) { - prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE); - - if (wait_drain(q, rl, wait_dispatch)) { - __generic_unplug_device(q); - spin_unlock_irq(q->queue_lock); - io_schedule(); - spin_lock_irq(q->queue_lock); - } - - finish_wait(&rl->drain, &wait); - } - - spin_unlock_irq(q->queue_lock); -} - -/* - * block waiting for the io scheduler being started again. - */ -static inline void block_wait_queue_running(request_queue_t *q) -{ - DEFINE_WAIT(wait); - - while (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) { - struct request_list *rl = &q->rq; - - prepare_to_wait_exclusive(&rl->drain, &wait, - TASK_UNINTERRUPTIBLE); - - /* - * re-check the condition. avoids using prepare_to_wait() - * in the fast path (queue is running) - */ - if (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) - io_schedule(); - - finish_wait(&rl->drain, &wait); - } -} - static void handle_bad_sector(struct bio *bio) { char b[BDEVNAME_SIZE]; @@ -2988,8 +2902,6 @@ end_io: if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) goto end_io; - block_wait_queue_running(q); - /* * If this device has partitions, remap block n * of partition p to block n+start(p) of the disk. |