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>
8 #include <linux/slab.h>
9
10 #include "blk.h"
11
12 /**
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
16 *
17 * Notes:
18 * Should be used when a device returns a tag and you want to match
19 * it with a request.
20 *
21 * no locks need be held.
22 **/
blk_queue_find_tag(struct request_queue * q,int tag)23 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
24 {
25 return blk_map_queue_find_tag(q->queue_tags, tag);
26 }
27 EXPORT_SYMBOL(blk_queue_find_tag);
28
29 /**
30 * blk_free_tags - release a given set of tag maintenance info
31 * @bqt: the tag map to free
32 *
33 * Drop the reference count on @bqt and frees it when the last reference
34 * is dropped.
35 */
blk_free_tags(struct blk_queue_tag * bqt)36 void blk_free_tags(struct blk_queue_tag *bqt)
37 {
38 if (atomic_dec_and_test(&bqt->refcnt)) {
39 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
40 bqt->max_depth);
41
42 kfree(bqt->tag_index);
43 bqt->tag_index = NULL;
44
45 kfree(bqt->tag_map);
46 bqt->tag_map = NULL;
47
48 kfree(bqt);
49 }
50 }
51 EXPORT_SYMBOL(blk_free_tags);
52
53 /**
54 * __blk_queue_free_tags - release tag maintenance info
55 * @q: the request queue for the device
56 *
57 * Notes:
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.
60 **/
__blk_queue_free_tags(struct request_queue * q)61 void __blk_queue_free_tags(struct request_queue *q)
62 {
63 struct blk_queue_tag *bqt = q->queue_tags;
64
65 if (!bqt)
66 return;
67
68 blk_free_tags(bqt);
69
70 q->queue_tags = NULL;
71 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
72 }
73
74 /**
75 * blk_queue_free_tags - release tag maintenance info
76 * @q: the request queue for the device
77 *
78 * Notes:
79 * This is used to disable tagged queuing to a device, yet leave
80 * queue in function.
81 **/
blk_queue_free_tags(struct request_queue * q)82 void blk_queue_free_tags(struct request_queue *q)
83 {
84 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
85 }
86 EXPORT_SYMBOL(blk_queue_free_tags);
87
88 static int
init_tag_map(struct request_queue * q,struct blk_queue_tag * tags,int depth)89 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
90 {
91 struct request **tag_index;
92 unsigned long *tag_map;
93 int nr_ulongs;
94
95 if (q && depth > q->nr_requests * 2) {
96 depth = q->nr_requests * 2;
97 printk(KERN_ERR "%s: adjusted depth to %d\n",
98 __func__, depth);
99 }
100
101 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
102 if (!tag_index)
103 goto fail;
104
105 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
106 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
107 if (!tag_map)
108 goto fail;
109
110 tags->real_max_depth = depth;
111 tags->max_depth = depth;
112 tags->tag_index = tag_index;
113 tags->tag_map = tag_map;
114
115 return 0;
116 fail:
117 kfree(tag_index);
118 return -ENOMEM;
119 }
120
__blk_queue_init_tags(struct request_queue * q,int depth)121 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
122 int depth)
123 {
124 struct blk_queue_tag *tags;
125
126 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
127 if (!tags)
128 goto fail;
129
130 if (init_tag_map(q, tags, depth))
131 goto fail;
132
133 atomic_set(&tags->refcnt, 1);
134 return tags;
135 fail:
136 kfree(tags);
137 return NULL;
138 }
139
140 /**
141 * blk_init_tags - initialize the tag info for an external tag map
142 * @depth: the maximum queue depth supported
143 **/
blk_init_tags(int depth)144 struct blk_queue_tag *blk_init_tags(int depth)
145 {
146 return __blk_queue_init_tags(NULL, depth);
147 }
148 EXPORT_SYMBOL(blk_init_tags);
149
150 /**
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
155 *
156 * Queue lock must be held here if the function is called to resize an
157 * existing map.
158 **/
blk_queue_init_tags(struct request_queue * q,int depth,struct blk_queue_tag * tags)159 int blk_queue_init_tags(struct request_queue *q, int depth,
160 struct blk_queue_tag *tags)
161 {
162 int rc;
163
164 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
165
166 if (!tags && !q->queue_tags) {
167 tags = __blk_queue_init_tags(q, depth);
168
169 if (!tags)
170 return -ENOMEM;
171
172 } else if (q->queue_tags) {
173 rc = blk_queue_resize_tags(q, depth);
174 if (rc)
175 return rc;
176 queue_flag_set(QUEUE_FLAG_QUEUED, q);
177 return 0;
178 } else
179 atomic_inc(&tags->refcnt);
180
181 /*
182 * assign it, all done
183 */
184 q->queue_tags = tags;
185 queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
186 INIT_LIST_HEAD(&q->tag_busy_list);
187 return 0;
188 }
189 EXPORT_SYMBOL(blk_queue_init_tags);
190
191 /**
192 * blk_queue_resize_tags - change the queueing depth
193 * @q: the request queue for the device
194 * @new_depth: the new max command queueing depth
195 *
196 * Notes:
197 * Must be called with the queue lock held.
198 **/
blk_queue_resize_tags(struct request_queue * q,int new_depth)199 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
200 {
201 struct blk_queue_tag *bqt = q->queue_tags;
202 struct request **tag_index;
203 unsigned long *tag_map;
204 int max_depth, nr_ulongs;
205
206 if (!bqt)
207 return -ENXIO;
208
209 /*
210 * if we already have large enough real_max_depth. just
211 * adjust max_depth. *NOTE* as requests with tag value
212 * between new_depth and real_max_depth can be in-flight, tag
213 * map can not be shrunk blindly here.
214 */
215 if (new_depth <= bqt->real_max_depth) {
216 bqt->max_depth = new_depth;
217 return 0;
218 }
219
220 /*
221 * Currently cannot replace a shared tag map with a new
222 * one, so error out if this is the case
223 */
224 if (atomic_read(&bqt->refcnt) != 1)
225 return -EBUSY;
226
227 /*
228 * save the old state info, so we can copy it back
229 */
230 tag_index = bqt->tag_index;
231 tag_map = bqt->tag_map;
232 max_depth = bqt->real_max_depth;
233
234 if (init_tag_map(q, bqt, new_depth))
235 return -ENOMEM;
236
237 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
238 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
239 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
240
241 kfree(tag_index);
242 kfree(tag_map);
243 return 0;
244 }
245 EXPORT_SYMBOL(blk_queue_resize_tags);
246
247 /**
248 * blk_queue_end_tag - end tag operations for a request
249 * @q: the request queue for the device
250 * @rq: the request that has completed
251 *
252 * Description:
253 * Typically called when end_that_request_first() returns %0, meaning
254 * all transfers have been done for a request. It's important to call
255 * this function before end_that_request_last(), as that will put the
256 * request back on the free list thus corrupting the internal tag list.
257 *
258 * Notes:
259 * queue lock must be held.
260 **/
blk_queue_end_tag(struct request_queue * q,struct request * rq)261 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
262 {
263 struct blk_queue_tag *bqt = q->queue_tags;
264 unsigned tag = rq->tag; /* negative tags invalid */
265
266 BUG_ON(tag >= bqt->real_max_depth);
267
268 list_del_init(&rq->queuelist);
269 rq->cmd_flags &= ~REQ_QUEUED;
270 rq->tag = -1;
271
272 if (unlikely(bqt->tag_index[tag] == NULL))
273 printk(KERN_ERR "%s: tag %d is missing\n",
274 __func__, tag);
275
276 bqt->tag_index[tag] = NULL;
277
278 if (unlikely(!test_bit(tag, bqt->tag_map))) {
279 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
280 __func__, tag);
281 return;
282 }
283 /*
284 * The tag_map bit acts as a lock for tag_index[bit], so we need
285 * unlock memory barrier semantics.
286 */
287 clear_bit_unlock(tag, bqt->tag_map);
288 }
289 EXPORT_SYMBOL(blk_queue_end_tag);
290
291 /**
292 * blk_queue_start_tag - find a free tag and assign it
293 * @q: the request queue for the device
294 * @rq: the block request that needs tagging
295 *
296 * Description:
297 * This can either be used as a stand-alone helper, or possibly be
298 * assigned as the queue &prep_rq_fn (in which case &struct request
299 * automagically gets a tag assigned). Note that this function
300 * assumes that any type of request can be queued! if this is not
301 * true for your device, you must check the request type before
302 * calling this function. The request will also be removed from
303 * the request queue, so it's the drivers responsibility to readd
304 * it if it should need to be restarted for some reason.
305 *
306 * Notes:
307 * queue lock must be held.
308 **/
blk_queue_start_tag(struct request_queue * q,struct request * rq)309 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
310 {
311 struct blk_queue_tag *bqt = q->queue_tags;
312 unsigned max_depth;
313 int tag;
314
315 if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
316 printk(KERN_ERR
317 "%s: request %p for device [%s] already tagged %d",
318 __func__, rq,
319 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
320 BUG();
321 }
322
323 /*
324 * Protect against shared tag maps, as we may not have exclusive
325 * access to the tag map.
326 *
327 * We reserve a few tags just for sync IO, since we don't want
328 * to starve sync IO on behalf of flooding async IO.
329 */
330 max_depth = bqt->max_depth;
331 if (!rq_is_sync(rq) && max_depth > 1) {
332 switch (max_depth) {
333 case 2:
334 max_depth = 1;
335 break;
336 case 3:
337 max_depth = 2;
338 break;
339 default:
340 max_depth -= 2;
341 }
342 if (q->in_flight[BLK_RW_ASYNC] > max_depth)
343 return 1;
344 }
345
346 do {
347 tag = find_first_zero_bit(bqt->tag_map, max_depth);
348 if (tag >= max_depth)
349 return 1;
350
351 } while (test_and_set_bit_lock(tag, bqt->tag_map));
352 /*
353 * We need lock ordering semantics given by test_and_set_bit_lock.
354 * See blk_queue_end_tag for details.
355 */
356
357 rq->cmd_flags |= REQ_QUEUED;
358 rq->tag = tag;
359 bqt->tag_index[tag] = rq;
360 blk_start_request(rq);
361 list_add(&rq->queuelist, &q->tag_busy_list);
362 return 0;
363 }
364 EXPORT_SYMBOL(blk_queue_start_tag);
365
366 /**
367 * blk_queue_invalidate_tags - invalidate all pending tags
368 * @q: the request queue for the device
369 *
370 * Description:
371 * Hardware conditions may dictate a need to stop all pending requests.
372 * In this case, we will safely clear the block side of the tag queue and
373 * readd all requests to the request queue in the right order.
374 *
375 * Notes:
376 * queue lock must be held.
377 **/
blk_queue_invalidate_tags(struct request_queue * q)378 void blk_queue_invalidate_tags(struct request_queue *q)
379 {
380 struct list_head *tmp, *n;
381
382 list_for_each_safe(tmp, n, &q->tag_busy_list)
383 blk_requeue_request(q, list_entry_rq(tmp));
384 }
385 EXPORT_SYMBOL(blk_queue_invalidate_tags);
386