blob: f0344e6939d537ecaac05c21a0542c46d37d2808
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->cmd_flags &= ~REQ_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->cmd_flags & REQ_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->cmd_flags |= REQ_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); |
403 |