diff options
Diffstat (limited to 'block/blk-tag.c')
| -rw-r--r-- | block/blk-tag.c | 406 |
1 files changed, 406 insertions, 0 deletions
diff --git a/block/blk-tag.c b/block/blk-tag.c new file mode 100644 index 00000000..ece65fc4 --- /dev/null +++ b/block/blk-tag.c @@ -0,0 +1,406 @@ +/* + * Functions related to tagged command queuing + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/bio.h> +#include <linux/blkdev.h> +#include <linux/slab.h> + +#include "blk.h" + +/** + * blk_queue_find_tag - find a request by its tag and queue + * @q: The request queue for the device + * @tag: The tag of the request + * + * Notes: + * Should be used when a device returns a tag and you want to match + * it with a request. + * + * no locks need be held. + **/ +struct request *blk_queue_find_tag(struct request_queue *q, int tag) +{ + return blk_map_queue_find_tag(q->queue_tags, tag); +} +EXPORT_SYMBOL(blk_queue_find_tag); + +/** + * __blk_free_tags - release a given set of tag maintenance info + * @bqt: the tag map to free + * + * Tries to free the specified @bqt. Returns true if it was + * actually freed and false if there are still references using it + */ +static int __blk_free_tags(struct blk_queue_tag *bqt) +{ + int retval; + + retval = atomic_dec_and_test(&bqt->refcnt); + if (retval) { + BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) < + bqt->max_depth); + + kfree(bqt->tag_index); + bqt->tag_index = NULL; + + kfree(bqt->tag_map); + bqt->tag_map = NULL; + + kfree(bqt); + } + + return retval; +} + +/** + * __blk_queue_free_tags - release tag maintenance info + * @q: the request queue for the device + * + * Notes: + * blk_cleanup_queue() will take care of calling this function, if tagging + * has been used. So there's no need to call this directly. + **/ +void __blk_queue_free_tags(struct request_queue *q) +{ + struct blk_queue_tag *bqt = q->queue_tags; + + if (!bqt) + return; + + __blk_free_tags(bqt); + + q->queue_tags = NULL; + queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q); +} + +/** + * blk_free_tags - release a given set of tag maintenance info + * @bqt: the tag map to free + * + * For externally managed @bqt frees the map. Callers of this + * function must guarantee to have released all the queues that + * might have been using this tag map. + */ +void blk_free_tags(struct blk_queue_tag *bqt) +{ + if (unlikely(!__blk_free_tags(bqt))) + BUG(); +} +EXPORT_SYMBOL(blk_free_tags); + +/** + * blk_queue_free_tags - release tag maintenance info + * @q: the request queue for the device + * + * Notes: + * This is used to disable tagged queuing to a device, yet leave + * queue in function. + **/ +void blk_queue_free_tags(struct request_queue *q) +{ + queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q); +} +EXPORT_SYMBOL(blk_queue_free_tags); + +static int +init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth) +{ + struct request **tag_index; + unsigned long *tag_map; + int nr_ulongs; + + if (q && depth > q->nr_requests * 2) { + depth = q->nr_requests * 2; + printk(KERN_ERR "%s: adjusted depth to %d\n", + __func__, depth); + } + + tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC); + if (!tag_index) + goto fail; + + nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG; + tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC); + if (!tag_map) + goto fail; + + tags->real_max_depth = depth; + tags->max_depth = depth; + tags->tag_index = tag_index; + tags->tag_map = tag_map; + + return 0; +fail: + kfree(tag_index); + return -ENOMEM; +} + +static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, + int depth) +{ + struct blk_queue_tag *tags; + + tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC); + if (!tags) + goto fail; + + if (init_tag_map(q, tags, depth)) + goto fail; + + atomic_set(&tags->refcnt, 1); + return tags; +fail: + kfree(tags); + return NULL; +} + +/** + * blk_init_tags - initialize the tag info for an external tag map + * @depth: the maximum queue depth supported + **/ +struct blk_queue_tag *blk_init_tags(int depth) +{ + return __blk_queue_init_tags(NULL, depth); +} +EXPORT_SYMBOL(blk_init_tags); + +/** + * blk_queue_init_tags - initialize the queue tag info + * @q: the request queue for the device + * @depth: the maximum queue depth supported + * @tags: the tag to use + * + * Queue lock must be held here if the function is called to resize an + * existing map. + **/ +int blk_queue_init_tags(struct request_queue *q, int depth, + struct blk_queue_tag *tags) +{ + int rc; + + BUG_ON(tags && q->queue_tags && tags != q->queue_tags); + + if (!tags && !q->queue_tags) { + tags = __blk_queue_init_tags(q, depth); + + if (!tags) + goto fail; + } else if (q->queue_tags) { + rc = blk_queue_resize_tags(q, depth); + if (rc) + return rc; + queue_flag_set(QUEUE_FLAG_QUEUED, q); + return 0; + } else + atomic_inc(&tags->refcnt); + + /* + * assign it, all done + */ + q->queue_tags = tags; + queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q); + INIT_LIST_HEAD(&q->tag_busy_list); + return 0; +fail: + kfree(tags); + return -ENOMEM; +} +EXPORT_SYMBOL(blk_queue_init_tags); + +/** + * blk_queue_resize_tags - change the queueing depth + * @q: the request queue for the device + * @new_depth: the new max command queueing depth + * + * Notes: + * Must be called with the queue lock held. + **/ +int blk_queue_resize_tags(struct request_queue *q, int new_depth) +{ + struct blk_queue_tag *bqt = q->queue_tags; + struct request **tag_index; + unsigned long *tag_map; + int max_depth, nr_ulongs; + + if (!bqt) + return -ENXIO; + + /* + * if we already have large enough real_max_depth. just + * adjust max_depth. *NOTE* as requests with tag value + * between new_depth and real_max_depth can be in-flight, tag + * map can not be shrunk blindly here. + */ + if (new_depth <= bqt->real_max_depth) { + bqt->max_depth = new_depth; + return 0; + } + + /* + * Currently cannot replace a shared tag map with a new + * one, so error out if this is the case + */ + if (atomic_read(&bqt->refcnt) != 1) + return -EBUSY; + + /* + * save the old state info, so we can copy it back + */ + tag_index = bqt->tag_index; + tag_map = bqt->tag_map; + max_depth = bqt->real_max_depth; + + if (init_tag_map(q, bqt, new_depth)) + return -ENOMEM; + + memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *)); + nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG; + memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long)); + + kfree(tag_index); + kfree(tag_map); + return 0; +} +EXPORT_SYMBOL(blk_queue_resize_tags); + +/** + * blk_queue_end_tag - end tag operations for a request + * @q: the request queue for the device + * @rq: the request that has completed + * + * Description: + * Typically called when end_that_request_first() returns %0, meaning + * all transfers have been done for a request. It's important to call + * this function before end_that_request_last(), as that will put the + * request back on the free list thus corrupting the internal tag list. + * + * Notes: + * queue lock must be held. + **/ +void blk_queue_end_tag(struct request_queue *q, struct request *rq) +{ + struct blk_queue_tag *bqt = q->queue_tags; + int tag = rq->tag; + + BUG_ON(tag == -1); + + if (unlikely(tag >= bqt->real_max_depth)) + /* + * This can happen after tag depth has been reduced. + * FIXME: how about a warning or info message here? + */ + return; + + list_del_init(&rq->queuelist); + rq->cmd_flags &= ~REQ_QUEUED; + rq->tag = -1; + + if (unlikely(bqt->tag_index[tag] == NULL)) + printk(KERN_ERR "%s: tag %d is missing\n", + __func__, tag); + + bqt->tag_index[tag] = NULL; + + if (unlikely(!test_bit(tag, bqt->tag_map))) { + printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", + __func__, tag); + return; + } + /* + * The tag_map bit acts as a lock for tag_index[bit], so we need + * unlock memory barrier semantics. + */ + clear_bit_unlock(tag, bqt->tag_map); +} +EXPORT_SYMBOL(blk_queue_end_tag); + +/** + * blk_queue_start_tag - find a free tag and assign it + * @q: the request queue for the device + * @rq: the block request that needs tagging + * + * Description: + * This can either be used as a stand-alone helper, or possibly be + * assigned as the queue &prep_rq_fn (in which case &struct request + * automagically gets a tag assigned). Note that this function + * assumes that any type of request can be queued! if this is not + * true for your device, you must check the request type before + * calling this function. The request will also be removed from + * the request queue, so it's the drivers responsibility to readd + * it if it should need to be restarted for some reason. + * + * Notes: + * queue lock must be held. + **/ +int blk_queue_start_tag(struct request_queue *q, struct request *rq) +{ + struct blk_queue_tag *bqt = q->queue_tags; + unsigned max_depth; + int tag; + + if (unlikely((rq->cmd_flags & REQ_QUEUED))) { + printk(KERN_ERR + "%s: request %p for device [%s] already tagged %d", + __func__, rq, + rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag); + BUG(); + } + + /* + * Protect against shared tag maps, as we may not have exclusive + * access to the tag map. + * + * We reserve a few tags just for sync IO, since we don't want + * to starve sync IO on behalf of flooding async IO. + */ + max_depth = bqt->max_depth; + if (!rq_is_sync(rq) && max_depth > 1) { + max_depth -= 2; + if (!max_depth) + max_depth = 1; + if (q->in_flight[BLK_RW_ASYNC] > max_depth) + return 1; + } + + do { + tag = find_first_zero_bit(bqt->tag_map, max_depth); + if (tag >= max_depth) + return 1; + + } while (test_and_set_bit_lock(tag, bqt->tag_map)); + /* + * We need lock ordering semantics given by test_and_set_bit_lock. + * See blk_queue_end_tag for details. + */ + + rq->cmd_flags |= REQ_QUEUED; + rq->tag = tag; + bqt->tag_index[tag] = rq; + blk_start_request(rq); + list_add(&rq->queuelist, &q->tag_busy_list); + return 0; +} +EXPORT_SYMBOL(blk_queue_start_tag); + +/** + * blk_queue_invalidate_tags - invalidate all pending tags + * @q: the request queue for the device + * + * Description: + * Hardware conditions may dictate a need to stop all pending requests. + * In this case, we will safely clear the block side of the tag queue and + * readd all requests to the request queue in the right order. + * + * Notes: + * queue lock must be held. + **/ +void blk_queue_invalidate_tags(struct request_queue *q) +{ + struct list_head *tmp, *n; + + list_for_each_safe(tmp, n, &q->tag_busy_list) + blk_requeue_request(q, list_entry_rq(tmp)); +} +EXPORT_SYMBOL(blk_queue_invalidate_tags); |