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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 | **/ | |
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 | */ | |
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 | **/ | |
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 | **/ | |
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 | |
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 | ||
121 | static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, | |
122 | int depth, int alloc_policy) | |
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 | tags->alloc_policy = alloc_policy; | |
135 | tags->next_tag = 0; | |
136 | return tags; | |
137 | fail: | |
138 | kfree(tags); | |
139 | return NULL; | |
140 | } | |
141 | ||
142 | /** | |
143 | * blk_init_tags - initialize the tag info for an external tag map | |
144 | * @depth: the maximum queue depth supported | |
145 | * @alloc_policy: tag allocation policy | |
146 | **/ | |
147 | struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy) | |
148 | { | |
149 | return __blk_queue_init_tags(NULL, depth, alloc_policy); | |
150 | } | |
151 | EXPORT_SYMBOL(blk_init_tags); | |
152 | ||
153 | /** | |
154 | * blk_queue_init_tags - initialize the queue tag info | |
155 | * @q: the request queue for the device | |
156 | * @depth: the maximum queue depth supported | |
157 | * @tags: the tag to use | |
158 | * @alloc_policy: tag allocation policy | |
159 | * | |
160 | * Queue lock must be held here if the function is called to resize an | |
161 | * existing map. | |
162 | **/ | |
163 | int blk_queue_init_tags(struct request_queue *q, int depth, | |
164 | struct blk_queue_tag *tags, int alloc_policy) | |
165 | { | |
166 | int rc; | |
167 | ||
168 | BUG_ON(tags && q->queue_tags && tags != q->queue_tags); | |
169 | ||
170 | if (!tags && !q->queue_tags) { | |
171 | tags = __blk_queue_init_tags(q, depth, alloc_policy); | |
172 | ||
173 | if (!tags) | |
174 | return -ENOMEM; | |
175 | ||
176 | } else if (q->queue_tags) { | |
177 | rc = blk_queue_resize_tags(q, depth); | |
178 | if (rc) | |
179 | return rc; | |
180 | queue_flag_set(QUEUE_FLAG_QUEUED, q); | |
181 | return 0; | |
182 | } else | |
183 | atomic_inc(&tags->refcnt); | |
184 | ||
185 | /* | |
186 | * assign it, all done | |
187 | */ | |
188 | q->queue_tags = tags; | |
189 | queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q); | |
190 | INIT_LIST_HEAD(&q->tag_busy_list); | |
191 | return 0; | |
192 | } | |
193 | EXPORT_SYMBOL(blk_queue_init_tags); | |
194 | ||
195 | /** | |
196 | * blk_queue_resize_tags - change the queueing depth | |
197 | * @q: the request queue for the device | |
198 | * @new_depth: the new max command queueing depth | |
199 | * | |
200 | * Notes: | |
201 | * Must be called with the queue lock held. | |
202 | **/ | |
203 | int blk_queue_resize_tags(struct request_queue *q, int new_depth) | |
204 | { | |
205 | struct blk_queue_tag *bqt = q->queue_tags; | |
206 | struct request **tag_index; | |
207 | unsigned long *tag_map; | |
208 | int max_depth, nr_ulongs; | |
209 | ||
210 | if (!bqt) | |
211 | return -ENXIO; | |
212 | ||
213 | /* | |
214 | * if we already have large enough real_max_depth. just | |
215 | * adjust max_depth. *NOTE* as requests with tag value | |
216 | * between new_depth and real_max_depth can be in-flight, tag | |
217 | * map can not be shrunk blindly here. | |
218 | */ | |
219 | if (new_depth <= bqt->real_max_depth) { | |
220 | bqt->max_depth = new_depth; | |
221 | return 0; | |
222 | } | |
223 | ||
224 | /* | |
225 | * Currently cannot replace a shared tag map with a new | |
226 | * one, so error out if this is the case | |
227 | */ | |
228 | if (atomic_read(&bqt->refcnt) != 1) | |
229 | return -EBUSY; | |
230 | ||
231 | /* | |
232 | * save the old state info, so we can copy it back | |
233 | */ | |
234 | tag_index = bqt->tag_index; | |
235 | tag_map = bqt->tag_map; | |
236 | max_depth = bqt->real_max_depth; | |
237 | ||
238 | if (init_tag_map(q, bqt, new_depth)) | |
239 | return -ENOMEM; | |
240 | ||
241 | memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *)); | |
242 | nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG; | |
243 | memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long)); | |
244 | ||
245 | kfree(tag_index); | |
246 | kfree(tag_map); | |
247 | return 0; | |
248 | } | |
249 | EXPORT_SYMBOL(blk_queue_resize_tags); | |
250 | ||
251 | /** | |
252 | * blk_queue_end_tag - end tag operations for a request | |
253 | * @q: the request queue for the device | |
254 | * @rq: the request that has completed | |
255 | * | |
256 | * Description: | |
257 | * Typically called when end_that_request_first() returns %0, meaning | |
258 | * all transfers have been done for a request. It's important to call | |
259 | * this function before end_that_request_last(), as that will put the | |
260 | * request back on the free list thus corrupting the internal tag list. | |
261 | * | |
262 | * Notes: | |
263 | * queue lock must be held. | |
264 | **/ | |
265 | void blk_queue_end_tag(struct request_queue *q, struct request *rq) | |
266 | { | |
267 | struct blk_queue_tag *bqt = q->queue_tags; | |
268 | unsigned tag = rq->tag; /* negative tags invalid */ | |
269 | ||
270 | BUG_ON(tag >= bqt->real_max_depth); | |
271 | ||
272 | list_del_init(&rq->queuelist); | |
273 | rq->rq_flags &= ~RQF_QUEUED; | |
274 | rq->tag = -1; | |
275 | ||
276 | if (unlikely(bqt->tag_index[tag] == NULL)) | |
277 | printk(KERN_ERR "%s: tag %d is missing\n", | |
278 | __func__, tag); | |
279 | ||
280 | bqt->tag_index[tag] = NULL; | |
281 | ||
282 | if (unlikely(!test_bit(tag, bqt->tag_map))) { | |
283 | printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", | |
284 | __func__, tag); | |
285 | return; | |
286 | } | |
287 | /* | |
288 | * The tag_map bit acts as a lock for tag_index[bit], so we need | |
289 | * unlock memory barrier semantics. | |
290 | */ | |
291 | clear_bit_unlock(tag, bqt->tag_map); | |
292 | } | |
293 | EXPORT_SYMBOL(blk_queue_end_tag); | |
294 | ||
295 | /** | |
296 | * blk_queue_start_tag - find a free tag and assign it | |
297 | * @q: the request queue for the device | |
298 | * @rq: the block request that needs tagging | |
299 | * | |
300 | * Description: | |
301 | * This can either be used as a stand-alone helper, or possibly be | |
302 | * assigned as the queue &prep_rq_fn (in which case &struct request | |
303 | * automagically gets a tag assigned). Note that this function | |
304 | * assumes that any type of request can be queued! if this is not | |
305 | * true for your device, you must check the request type before | |
306 | * calling this function. The request will also be removed from | |
307 | * the request queue, so it's the drivers responsibility to readd | |
308 | * it if it should need to be restarted for some reason. | |
309 | * | |
310 | * Notes: | |
311 | * queue lock must be held. | |
312 | **/ | |
313 | int blk_queue_start_tag(struct request_queue *q, struct request *rq) | |
314 | { | |
315 | struct blk_queue_tag *bqt = q->queue_tags; | |
316 | unsigned max_depth; | |
317 | int tag; | |
318 | ||
319 | if (unlikely((rq->rq_flags & RQF_QUEUED))) { | |
320 | printk(KERN_ERR | |
321 | "%s: request %p for device [%s] already tagged %d", | |
322 | __func__, rq, | |
323 | rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag); | |
324 | BUG(); | |
325 | } | |
326 | ||
327 | /* | |
328 | * Protect against shared tag maps, as we may not have exclusive | |
329 | * access to the tag map. | |
330 | * | |
331 | * We reserve a few tags just for sync IO, since we don't want | |
332 | * to starve sync IO on behalf of flooding async IO. | |
333 | */ | |
334 | max_depth = bqt->max_depth; | |
335 | if (!rq_is_sync(rq) && max_depth > 1) { | |
336 | switch (max_depth) { | |
337 | case 2: | |
338 | max_depth = 1; | |
339 | break; | |
340 | case 3: | |
341 | max_depth = 2; | |
342 | break; | |
343 | default: | |
344 | max_depth -= 2; | |
345 | } | |
346 | if (q->in_flight[BLK_RW_ASYNC] > max_depth) | |
347 | return 1; | |
348 | } | |
349 | ||
350 | do { | |
351 | if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) { | |
352 | tag = find_first_zero_bit(bqt->tag_map, max_depth); | |
353 | if (tag >= max_depth) | |
354 | return 1; | |
355 | } else { | |
356 | int start = bqt->next_tag; | |
357 | int size = min_t(int, bqt->max_depth, max_depth + start); | |
358 | tag = find_next_zero_bit(bqt->tag_map, size, start); | |
359 | if (tag >= size && start + size > bqt->max_depth) { | |
360 | size = start + size - bqt->max_depth; | |
361 | tag = find_first_zero_bit(bqt->tag_map, size); | |
362 | } | |
363 | if (tag >= size) | |
364 | return 1; | |
365 | } | |
366 | ||
367 | } while (test_and_set_bit_lock(tag, bqt->tag_map)); | |
368 | /* | |
369 | * We need lock ordering semantics given by test_and_set_bit_lock. | |
370 | * See blk_queue_end_tag for details. | |
371 | */ | |
372 | ||
373 | bqt->next_tag = (tag + 1) % bqt->max_depth; | |
374 | rq->rq_flags |= RQF_QUEUED; | |
375 | rq->tag = tag; | |
376 | bqt->tag_index[tag] = rq; | |
377 | blk_start_request(rq); | |
378 | list_add(&rq->queuelist, &q->tag_busy_list); | |
379 | return 0; | |
380 | } | |
381 | EXPORT_SYMBOL(blk_queue_start_tag); | |
382 | ||
383 | /** | |
384 | * blk_queue_invalidate_tags - invalidate all pending tags | |
385 | * @q: the request queue for the device | |
386 | * | |
387 | * Description: | |
388 | * Hardware conditions may dictate a need to stop all pending requests. | |
389 | * In this case, we will safely clear the block side of the tag queue and | |
390 | * readd all requests to the request queue in the right order. | |
391 | * | |
392 | * Notes: | |
393 | * queue lock must be held. | |
394 | **/ | |
395 | void blk_queue_invalidate_tags(struct request_queue *q) | |
396 | { | |
397 | struct list_head *tmp, *n; | |
398 | ||
399 | list_for_each_safe(tmp, n, &q->tag_busy_list) | |
400 | blk_requeue_request(q, list_entry_rq(tmp)); | |
401 | } | |
402 | EXPORT_SYMBOL(blk_queue_invalidate_tags); |