[ARM] S3C: Add UART FIFO selection during arch decompression
[linux-2.6/openmoko-kernel.git] / block / blk-tag.c
blobc0d419e84ce7f8518e1246e3ec61b07f5c81efe8
1 /*
2 * Functions related to tagged command queuing
3 */
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/bio.h>
7 #include <linux/blkdev.h>
9 #include "blk.h"
11 /**
12 * blk_queue_find_tag - find a request by its tag and queue
13 * @q: The request queue for the device
14 * @tag: The tag of the request
16 * Notes:
17 * Should be used when a device returns a tag and you want to match
18 * it with a request.
20 * no locks need be held.
21 **/
22 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
24 return blk_map_queue_find_tag(q->queue_tags, tag);
26 EXPORT_SYMBOL(blk_queue_find_tag);
28 /**
29 * __blk_free_tags - release a given set of tag maintenance info
30 * @bqt: the tag map to free
32 * Tries to free the specified @bqt. Returns true if it was
33 * actually freed and false if there are still references using it
35 static int __blk_free_tags(struct blk_queue_tag *bqt)
37 int retval;
39 retval = atomic_dec_and_test(&bqt->refcnt);
40 if (retval) {
41 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
42 bqt->max_depth);
44 kfree(bqt->tag_index);
45 bqt->tag_index = NULL;
47 kfree(bqt->tag_map);
48 bqt->tag_map = NULL;
50 kfree(bqt);
53 return retval;
56 /**
57 * __blk_queue_free_tags - release tag maintenance info
58 * @q: the request queue for the device
60 * Notes:
61 * blk_cleanup_queue() will take care of calling this function, if tagging
62 * has been used. So there's no need to call this directly.
63 **/
64 void __blk_queue_free_tags(struct request_queue *q)
66 struct blk_queue_tag *bqt = q->queue_tags;
68 if (!bqt)
69 return;
71 __blk_free_tags(bqt);
73 q->queue_tags = NULL;
74 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
77 /**
78 * blk_free_tags - release a given set of tag maintenance info
79 * @bqt: the tag map to free
81 * For externally managed @bqt frees the map. Callers of this
82 * function must guarantee to have released all the queues that
83 * might have been using this tag map.
85 void blk_free_tags(struct blk_queue_tag *bqt)
87 if (unlikely(!__blk_free_tags(bqt)))
88 BUG();
90 EXPORT_SYMBOL(blk_free_tags);
92 /**
93 * blk_queue_free_tags - release tag maintenance info
94 * @q: the request queue for the device
96 * Notes:
97 * This is used to disable tagged queuing to a device, yet leave
98 * queue in function.
99 **/
100 void blk_queue_free_tags(struct request_queue *q)
102 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
104 EXPORT_SYMBOL(blk_queue_free_tags);
106 static int
107 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
109 struct request **tag_index;
110 unsigned long *tag_map;
111 int nr_ulongs;
113 if (q && depth > q->nr_requests * 2) {
114 depth = q->nr_requests * 2;
115 printk(KERN_ERR "%s: adjusted depth to %d\n",
116 __func__, depth);
119 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
120 if (!tag_index)
121 goto fail;
123 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
124 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
125 if (!tag_map)
126 goto fail;
128 tags->real_max_depth = depth;
129 tags->max_depth = depth;
130 tags->tag_index = tag_index;
131 tags->tag_map = tag_map;
133 return 0;
134 fail:
135 kfree(tag_index);
136 return -ENOMEM;
139 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
140 int depth)
142 struct blk_queue_tag *tags;
144 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
145 if (!tags)
146 goto fail;
148 if (init_tag_map(q, tags, depth))
149 goto fail;
151 atomic_set(&tags->refcnt, 1);
152 return tags;
153 fail:
154 kfree(tags);
155 return NULL;
159 * blk_init_tags - initialize the tag info for an external tag map
160 * @depth: the maximum queue depth supported
161 * @tags: the tag to use
163 struct blk_queue_tag *blk_init_tags(int depth)
165 return __blk_queue_init_tags(NULL, depth);
167 EXPORT_SYMBOL(blk_init_tags);
170 * blk_queue_init_tags - initialize the queue tag info
171 * @q: the request queue for the device
172 * @depth: the maximum queue depth supported
173 * @tags: the tag to use
175 * Queue lock must be held here if the function is called to resize an
176 * existing map.
178 int blk_queue_init_tags(struct request_queue *q, int depth,
179 struct blk_queue_tag *tags)
181 int rc;
183 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
185 if (!tags && !q->queue_tags) {
186 tags = __blk_queue_init_tags(q, depth);
188 if (!tags)
189 goto fail;
190 } else if (q->queue_tags) {
191 rc = blk_queue_resize_tags(q, depth);
192 if (rc)
193 return rc;
194 queue_flag_set(QUEUE_FLAG_QUEUED, q);
195 return 0;
196 } else
197 atomic_inc(&tags->refcnt);
200 * assign it, all done
202 q->queue_tags = tags;
203 queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
204 INIT_LIST_HEAD(&q->tag_busy_list);
205 return 0;
206 fail:
207 kfree(tags);
208 return -ENOMEM;
210 EXPORT_SYMBOL(blk_queue_init_tags);
213 * blk_queue_resize_tags - change the queueing depth
214 * @q: the request queue for the device
215 * @new_depth: the new max command queueing depth
217 * Notes:
218 * Must be called with the queue lock held.
220 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
222 struct blk_queue_tag *bqt = q->queue_tags;
223 struct request **tag_index;
224 unsigned long *tag_map;
225 int max_depth, nr_ulongs;
227 if (!bqt)
228 return -ENXIO;
231 * if we already have large enough real_max_depth. just
232 * adjust max_depth. *NOTE* as requests with tag value
233 * between new_depth and real_max_depth can be in-flight, tag
234 * map can not be shrunk blindly here.
236 if (new_depth <= bqt->real_max_depth) {
237 bqt->max_depth = new_depth;
238 return 0;
242 * Currently cannot replace a shared tag map with a new
243 * one, so error out if this is the case
245 if (atomic_read(&bqt->refcnt) != 1)
246 return -EBUSY;
249 * save the old state info, so we can copy it back
251 tag_index = bqt->tag_index;
252 tag_map = bqt->tag_map;
253 max_depth = bqt->real_max_depth;
255 if (init_tag_map(q, bqt, new_depth))
256 return -ENOMEM;
258 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
259 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
260 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
262 kfree(tag_index);
263 kfree(tag_map);
264 return 0;
266 EXPORT_SYMBOL(blk_queue_resize_tags);
269 * blk_queue_end_tag - end tag operations for a request
270 * @q: the request queue for the device
271 * @rq: the request that has completed
273 * Description:
274 * Typically called when end_that_request_first() returns %0, meaning
275 * all transfers have been done for a request. It's important to call
276 * this function before end_that_request_last(), as that will put the
277 * request back on the free list thus corrupting the internal tag list.
279 * Notes:
280 * queue lock must be held.
282 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
284 struct blk_queue_tag *bqt = q->queue_tags;
285 int tag = rq->tag;
287 BUG_ON(tag == -1);
289 if (unlikely(tag >= bqt->real_max_depth))
291 * This can happen after tag depth has been reduced.
292 * FIXME: how about a warning or info message here?
294 return;
296 list_del_init(&rq->queuelist);
297 rq->cmd_flags &= ~REQ_QUEUED;
298 rq->tag = -1;
300 if (unlikely(bqt->tag_index[tag] == NULL))
301 printk(KERN_ERR "%s: tag %d is missing\n",
302 __func__, tag);
304 bqt->tag_index[tag] = NULL;
306 if (unlikely(!test_bit(tag, bqt->tag_map))) {
307 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
308 __func__, tag);
309 return;
312 * The tag_map bit acts as a lock for tag_index[bit], so we need
313 * unlock memory barrier semantics.
315 clear_bit_unlock(tag, bqt->tag_map);
317 EXPORT_SYMBOL(blk_queue_end_tag);
320 * blk_queue_start_tag - find a free tag and assign it
321 * @q: the request queue for the device
322 * @rq: the block request that needs tagging
324 * Description:
325 * This can either be used as a stand-alone helper, or possibly be
326 * assigned as the queue &prep_rq_fn (in which case &struct request
327 * automagically gets a tag assigned). Note that this function
328 * assumes that any type of request can be queued! if this is not
329 * true for your device, you must check the request type before
330 * calling this function. The request will also be removed from
331 * the request queue, so it's the drivers responsibility to readd
332 * it if it should need to be restarted for some reason.
334 * Notes:
335 * queue lock must be held.
337 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
339 struct blk_queue_tag *bqt = q->queue_tags;
340 unsigned max_depth, offset;
341 int tag;
343 if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
344 printk(KERN_ERR
345 "%s: request %p for device [%s] already tagged %d",
346 __func__, rq,
347 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
348 BUG();
352 * Protect against shared tag maps, as we may not have exclusive
353 * access to the tag map.
355 * We reserve a few tags just for sync IO, since we don't want
356 * to starve sync IO on behalf of flooding async IO.
358 max_depth = bqt->max_depth;
359 if (rq_is_sync(rq))
360 offset = 0;
361 else
362 offset = max_depth >> 2;
364 do {
365 tag = find_next_zero_bit(bqt->tag_map, max_depth, offset);
366 if (tag >= max_depth)
367 return 1;
369 } while (test_and_set_bit_lock(tag, bqt->tag_map));
371 * We need lock ordering semantics given by test_and_set_bit_lock.
372 * See blk_queue_end_tag for details.
375 rq->cmd_flags |= REQ_QUEUED;
376 rq->tag = tag;
377 bqt->tag_index[tag] = rq;
378 blkdev_dequeue_request(rq);
379 list_add(&rq->queuelist, &q->tag_busy_list);
380 return 0;
382 EXPORT_SYMBOL(blk_queue_start_tag);
385 * blk_queue_invalidate_tags - invalidate all pending tags
386 * @q: the request queue for the device
388 * Description:
389 * Hardware conditions may dictate a need to stop all pending requests.
390 * In this case, we will safely clear the block side of the tag queue and
391 * readd all requests to the request queue in the right order.
393 * Notes:
394 * queue lock must be held.
396 void blk_queue_invalidate_tags(struct request_queue *q)
398 struct list_head *tmp, *n;
400 list_for_each_safe(tmp, n, &q->tag_busy_list)
401 blk_requeue_request(q, list_entry_rq(tmp));
403 EXPORT_SYMBOL(blk_queue_invalidate_tags);