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 * Tries to free the specified @bqt. Returns true if it was
34 * actually freed and false if there are still references using it
35 */
__blk_free_tags(struct blk_queue_tag * bqt)36 static int __blk_free_tags(struct blk_queue_tag *bqt)
37 {
38 int retval;
39
40 retval = atomic_dec_and_test(&bqt->refcnt);
41 if (retval) {
42 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
43 bqt->max_depth);
44
45 kfree(bqt->tag_index);
46 bqt->tag_index = NULL;
47
48 kfree(bqt->tag_map);
49 bqt->tag_map = NULL;
50
51 kfree(bqt);
52 }
53
54 return retval;
55 }
56
57 /**
58 * __blk_queue_free_tags - release tag maintenance info
59 * @q: the request queue for the device
60 *
61 * Notes:
62 * blk_cleanup_queue() will take care of calling this function, if tagging
63 * has been used. So there's no need to call this directly.
64 **/
__blk_queue_free_tags(struct request_queue * q)65 void __blk_queue_free_tags(struct request_queue *q)
66 {
67 struct blk_queue_tag *bqt = q->queue_tags;
68
69 if (!bqt)
70 return;
71
72 __blk_free_tags(bqt);
73
74 q->queue_tags = NULL;
75 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
76 }
77
78 /**
79 * blk_free_tags - release a given set of tag maintenance info
80 * @bqt: the tag map to free
81 *
82 * For externally managed @bqt frees the map. Callers of this
83 * function must guarantee to have released all the queues that
84 * might have been using this tag map.
85 */
blk_free_tags(struct blk_queue_tag * bqt)86 void blk_free_tags(struct blk_queue_tag *bqt)
87 {
88 if (unlikely(!__blk_free_tags(bqt)))
89 BUG();
90 }
91 EXPORT_SYMBOL(blk_free_tags);
92
93 /**
94 * blk_queue_free_tags - release tag maintenance info
95 * @q: the request queue for the device
96 *
97 * Notes:
98 * This is used to disable tagged queuing to a device, yet leave
99 * queue in function.
100 **/
blk_queue_free_tags(struct request_queue * q)101 void blk_queue_free_tags(struct request_queue *q)
102 {
103 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
104 }
105 EXPORT_SYMBOL(blk_queue_free_tags);
106
107 static int
init_tag_map(struct request_queue * q,struct blk_queue_tag * tags,int depth)108 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
109 {
110 struct request **tag_index;
111 unsigned long *tag_map;
112 int nr_ulongs;
113
114 if (q && depth > q->nr_requests * 2) {
115 depth = q->nr_requests * 2;
116 printk(KERN_ERR "%s: adjusted depth to %d\n",
117 __func__, depth);
118 }
119
120 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
121 if (!tag_index)
122 goto fail;
123
124 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
125 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
126 if (!tag_map)
127 goto fail;
128
129 tags->real_max_depth = depth;
130 tags->max_depth = depth;
131 tags->tag_index = tag_index;
132 tags->tag_map = tag_map;
133
134 return 0;
135 fail:
136 kfree(tag_index);
137 return -ENOMEM;
138 }
139
__blk_queue_init_tags(struct request_queue * q,int depth)140 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
141 int depth)
142 {
143 struct blk_queue_tag *tags;
144
145 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
146 if (!tags)
147 goto fail;
148
149 if (init_tag_map(q, tags, depth))
150 goto fail;
151
152 atomic_set(&tags->refcnt, 1);
153 return tags;
154 fail:
155 kfree(tags);
156 return NULL;
157 }
158
159 /**
160 * blk_init_tags - initialize the tag info for an external tag map
161 * @depth: the maximum queue depth supported
162 **/
blk_init_tags(int depth)163 struct blk_queue_tag *blk_init_tags(int depth)
164 {
165 return __blk_queue_init_tags(NULL, depth);
166 }
167 EXPORT_SYMBOL(blk_init_tags);
168
169 /**
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
174 *
175 * Queue lock must be held here if the function is called to resize an
176 * existing map.
177 **/
blk_queue_init_tags(struct request_queue * q,int depth,struct blk_queue_tag * tags)178 int blk_queue_init_tags(struct request_queue *q, int depth,
179 struct blk_queue_tag *tags)
180 {
181 int rc;
182
183 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
184
185 if (!tags && !q->queue_tags) {
186 tags = __blk_queue_init_tags(q, depth);
187
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);
198
199 /*
200 * assign it, all done
201 */
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;
209 }
210 EXPORT_SYMBOL(blk_queue_init_tags);
211
212 /**
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
216 *
217 * Notes:
218 * Must be called with the queue lock held.
219 **/
blk_queue_resize_tags(struct request_queue * q,int new_depth)220 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
221 {
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;
226
227 if (!bqt)
228 return -ENXIO;
229
230 /*
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.
235 */
236 if (new_depth <= bqt->real_max_depth) {
237 bqt->max_depth = new_depth;
238 return 0;
239 }
240
241 /*
242 * Currently cannot replace a shared tag map with a new
243 * one, so error out if this is the case
244 */
245 if (atomic_read(&bqt->refcnt) != 1)
246 return -EBUSY;
247
248 /*
249 * save the old state info, so we can copy it back
250 */
251 tag_index = bqt->tag_index;
252 tag_map = bqt->tag_map;
253 max_depth = bqt->real_max_depth;
254
255 if (init_tag_map(q, bqt, new_depth))
256 return -ENOMEM;
257
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));
261
262 kfree(tag_index);
263 kfree(tag_map);
264 return 0;
265 }
266 EXPORT_SYMBOL(blk_queue_resize_tags);
267
268 /**
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
272 *
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.
278 *
279 * Notes:
280 * queue lock must be held.
281 **/
blk_queue_end_tag(struct request_queue * q,struct request * rq)282 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
283 {
284 struct blk_queue_tag *bqt = q->queue_tags;
285 unsigned tag = rq->tag; /* negative tags invalid */
286
287 BUG_ON(tag >= bqt->real_max_depth);
288
289 list_del_init(&rq->queuelist);
290 rq->cmd_flags &= ~REQ_QUEUED;
291 rq->tag = -1;
292
293 if (unlikely(bqt->tag_index[tag] == NULL))
294 printk(KERN_ERR "%s: tag %d is missing\n",
295 __func__, tag);
296
297 bqt->tag_index[tag] = NULL;
298
299 if (unlikely(!test_bit(tag, bqt->tag_map))) {
300 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
301 __func__, tag);
302 return;
303 }
304 /*
305 * The tag_map bit acts as a lock for tag_index[bit], so we need
306 * unlock memory barrier semantics.
307 */
308 clear_bit_unlock(tag, bqt->tag_map);
309 }
310 EXPORT_SYMBOL(blk_queue_end_tag);
311
312 /**
313 * blk_queue_start_tag - find a free tag and assign it
314 * @q: the request queue for the device
315 * @rq: the block request that needs tagging
316 *
317 * Description:
318 * This can either be used as a stand-alone helper, or possibly be
319 * assigned as the queue &prep_rq_fn (in which case &struct request
320 * automagically gets a tag assigned). Note that this function
321 * assumes that any type of request can be queued! if this is not
322 * true for your device, you must check the request type before
323 * calling this function. The request will also be removed from
324 * the request queue, so it's the drivers responsibility to readd
325 * it if it should need to be restarted for some reason.
326 *
327 * Notes:
328 * queue lock must be held.
329 **/
blk_queue_start_tag(struct request_queue * q,struct request * rq)330 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
331 {
332 struct blk_queue_tag *bqt = q->queue_tags;
333 unsigned max_depth;
334 int tag;
335
336 if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
337 printk(KERN_ERR
338 "%s: request %p for device [%s] already tagged %d",
339 __func__, rq,
340 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
341 BUG();
342 }
343
344 /*
345 * Protect against shared tag maps, as we may not have exclusive
346 * access to the tag map.
347 *
348 * We reserve a few tags just for sync IO, since we don't want
349 * to starve sync IO on behalf of flooding async IO.
350 */
351 max_depth = bqt->max_depth;
352 if (!rq_is_sync(rq) && max_depth > 1) {
353 max_depth -= 2;
354 if (!max_depth)
355 max_depth = 1;
356 if (q->in_flight[BLK_RW_ASYNC] > max_depth)
357 return 1;
358 }
359
360 do {
361 tag = find_first_zero_bit(bqt->tag_map, max_depth);
362 if (tag >= max_depth)
363 return 1;
364
365 } while (test_and_set_bit_lock(tag, bqt->tag_map));
366 /*
367 * We need lock ordering semantics given by test_and_set_bit_lock.
368 * See blk_queue_end_tag for details.
369 */
370
371 rq->cmd_flags |= REQ_QUEUED;
372 rq->tag = tag;
373 bqt->tag_index[tag] = rq;
374 blk_start_request(rq);
375 list_add(&rq->queuelist, &q->tag_busy_list);
376 return 0;
377 }
378 EXPORT_SYMBOL(blk_queue_start_tag);
379
380 /**
381 * blk_queue_invalidate_tags - invalidate all pending tags
382 * @q: the request queue for the device
383 *
384 * Description:
385 * Hardware conditions may dictate a need to stop all pending requests.
386 * In this case, we will safely clear the block side of the tag queue and
387 * readd all requests to the request queue in the right order.
388 *
389 * Notes:
390 * queue lock must be held.
391 **/
blk_queue_invalidate_tags(struct request_queue * q)392 void blk_queue_invalidate_tags(struct request_queue *q)
393 {
394 struct list_head *tmp, *n;
395
396 list_for_each_safe(tmp, n, &q->tag_busy_list)
397 blk_requeue_request(q, list_entry_rq(tmp));
398 }
399 EXPORT_SYMBOL(blk_queue_invalidate_tags);
400