2 * Functions related to tagged command queuing
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
8 #include <linux/slab.h>
13 * blk_queue_find_tag - find a request by its tag and queue
14 * @q: The request queue for the device
15 * @tag: The tag of the request
18 * Should be used when a device returns a tag and you want to match
21 * no locks need be held.
23 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
25 return blk_map_queue_find_tag(q->queue_tags, tag);
27 EXPORT_SYMBOL(blk_queue_find_tag);
30 * blk_free_tags - release a given set of tag maintenance info
31 * @bqt: the tag map to free
33 * Drop the reference count on @bqt and frees it when the last reference
36 void blk_free_tags(struct blk_queue_tag *bqt)
38 if (atomic_dec_and_test(&bqt->refcnt)) {
39 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
42 kfree(bqt->tag_index);
43 bqt->tag_index = NULL;
51 EXPORT_SYMBOL(blk_free_tags);
54 * __blk_queue_free_tags - release tag maintenance info
55 * @q: the request queue for the device
58 * blk_cleanup_queue() will take care of calling this function, if tagging
59 * has been used. So there's no need to call this directly.
61 void __blk_queue_free_tags(struct request_queue *q)
63 struct blk_queue_tag *bqt = q->queue_tags;
71 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
75 * blk_queue_free_tags - release tag maintenance info
76 * @q: the request queue for the device
79 * This is used to disable tagged queuing to a device, yet leave
82 void blk_queue_free_tags(struct request_queue *q)
84 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
86 EXPORT_SYMBOL(blk_queue_free_tags);
89 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
91 struct request **tag_index;
92 unsigned long *tag_map;
95 if (q && depth > q->nr_requests * 2) {
96 depth = q->nr_requests * 2;
97 printk(KERN_ERR "%s: adjusted depth to %d\n",
101 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
105 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
106 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
110 tags->real_max_depth = depth;
111 tags->max_depth = depth;
112 tags->tag_index = tag_index;
113 tags->tag_map = tag_map;
121 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
124 struct blk_queue_tag *tags;
126 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
130 if (init_tag_map(q, tags, depth))
133 atomic_set(&tags->refcnt, 1);
141 * blk_init_tags - initialize the tag info for an external tag map
142 * @depth: the maximum queue depth supported
144 struct blk_queue_tag *blk_init_tags(int depth)
146 return __blk_queue_init_tags(NULL, depth);
148 EXPORT_SYMBOL(blk_init_tags);
151 * blk_queue_init_tags - initialize the queue tag info
152 * @q: the request queue for the device
153 * @depth: the maximum queue depth supported
154 * @tags: the tag to use
156 * Queue lock must be held here if the function is called to resize an
159 int blk_queue_init_tags(struct request_queue *q, int depth,
160 struct blk_queue_tag *tags)
164 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
166 if (!tags && !q->queue_tags) {
167 tags = __blk_queue_init_tags(q, depth);
171 } else if (q->queue_tags) {
172 rc = blk_queue_resize_tags(q, depth);
175 queue_flag_set(QUEUE_FLAG_QUEUED, q);
178 atomic_inc(&tags->refcnt);
181 * assign it, all done
183 q->queue_tags = tags;
184 queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
185 INIT_LIST_HEAD(&q->tag_busy_list);
191 EXPORT_SYMBOL(blk_queue_init_tags);
194 * blk_queue_resize_tags - change the queueing depth
195 * @q: the request queue for the device
196 * @new_depth: the new max command queueing depth
199 * Must be called with the queue lock held.
201 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
203 struct blk_queue_tag *bqt = q->queue_tags;
204 struct request **tag_index;
205 unsigned long *tag_map;
206 int max_depth, nr_ulongs;
212 * if we already have large enough real_max_depth. just
213 * adjust max_depth. *NOTE* as requests with tag value
214 * between new_depth and real_max_depth can be in-flight, tag
215 * map can not be shrunk blindly here.
217 if (new_depth <= bqt->real_max_depth) {
218 bqt->max_depth = new_depth;
223 * Currently cannot replace a shared tag map with a new
224 * one, so error out if this is the case
226 if (atomic_read(&bqt->refcnt) != 1)
230 * save the old state info, so we can copy it back
232 tag_index = bqt->tag_index;
233 tag_map = bqt->tag_map;
234 max_depth = bqt->real_max_depth;
236 if (init_tag_map(q, bqt, new_depth))
239 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
240 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
241 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
247 EXPORT_SYMBOL(blk_queue_resize_tags);
250 * blk_queue_end_tag - end tag operations for a request
251 * @q: the request queue for the device
252 * @rq: the request that has completed
255 * Typically called when end_that_request_first() returns %0, meaning
256 * all transfers have been done for a request. It's important to call
257 * this function before end_that_request_last(), as that will put the
258 * request back on the free list thus corrupting the internal tag list.
261 * queue lock must be held.
263 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
265 struct blk_queue_tag *bqt = q->queue_tags;
266 unsigned tag = rq->tag; /* negative tags invalid */
268 BUG_ON(tag >= bqt->real_max_depth);
270 list_del_init(&rq->queuelist);
271 rq->cmd_flags &= ~REQ_QUEUED;
274 if (unlikely(bqt->tag_index[tag] == NULL))
275 printk(KERN_ERR "%s: tag %d is missing\n",
278 bqt->tag_index[tag] = NULL;
280 if (unlikely(!test_bit(tag, bqt->tag_map))) {
281 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
286 * The tag_map bit acts as a lock for tag_index[bit], so we need
287 * unlock memory barrier semantics.
289 clear_bit_unlock(tag, bqt->tag_map);
291 EXPORT_SYMBOL(blk_queue_end_tag);
294 * blk_queue_start_tag - find a free tag and assign it
295 * @q: the request queue for the device
296 * @rq: the block request that needs tagging
299 * This can either be used as a stand-alone helper, or possibly be
300 * assigned as the queue &prep_rq_fn (in which case &struct request
301 * automagically gets a tag assigned). Note that this function
302 * assumes that any type of request can be queued! if this is not
303 * true for your device, you must check the request type before
304 * calling this function. The request will also be removed from
305 * the request queue, so it's the drivers responsibility to readd
306 * it if it should need to be restarted for some reason.
309 * queue lock must be held.
311 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
313 struct blk_queue_tag *bqt = q->queue_tags;
317 if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
319 "%s: request %p for device [%s] already tagged %d",
321 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
326 * Protect against shared tag maps, as we may not have exclusive
327 * access to the tag map.
329 * We reserve a few tags just for sync IO, since we don't want
330 * to starve sync IO on behalf of flooding async IO.
332 max_depth = bqt->max_depth;
333 if (!rq_is_sync(rq) && max_depth > 1) {
337 if (q->in_flight[BLK_RW_ASYNC] > max_depth)
342 tag = find_first_zero_bit(bqt->tag_map, max_depth);
343 if (tag >= max_depth)
346 } while (test_and_set_bit_lock(tag, bqt->tag_map));
348 * We need lock ordering semantics given by test_and_set_bit_lock.
349 * See blk_queue_end_tag for details.
352 rq->cmd_flags |= REQ_QUEUED;
354 bqt->tag_index[tag] = rq;
355 blk_start_request(rq);
356 list_add(&rq->queuelist, &q->tag_busy_list);
359 EXPORT_SYMBOL(blk_queue_start_tag);
362 * blk_queue_invalidate_tags - invalidate all pending tags
363 * @q: the request queue for the device
366 * Hardware conditions may dictate a need to stop all pending requests.
367 * In this case, we will safely clear the block side of the tag queue and
368 * readd all requests to the request queue in the right order.
371 * queue lock must be held.
373 void blk_queue_invalidate_tags(struct request_queue *q)
375 struct list_head *tmp, *n;
377 list_for_each_safe(tmp, n, &q->tag_busy_list)
378 blk_requeue_request(q, list_entry_rq(tmp));
380 EXPORT_SYMBOL(blk_queue_invalidate_tags);