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