1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Functions related to tagged command queuing
4 */
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/bio.h>
8 #include <linux/blkdev.h>
9 #include <linux/slab.h>
10
11 #include "blk.h"
12
13 /**
14 * blk_queue_find_tag - find a request by its tag and queue
15 * @q: The request queue for the device
16 * @tag: The tag of the request
17 *
18 * Notes:
19 * Should be used when a device returns a tag and you want to match
20 * it with a request.
21 *
22 * no locks need be held.
23 **/
blk_queue_find_tag(struct request_queue * q,int tag)24 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
25 {
26 return blk_map_queue_find_tag(q->queue_tags, tag);
27 }
28 EXPORT_SYMBOL(blk_queue_find_tag);
29
30 /**
31 * blk_free_tags - release a given set of tag maintenance info
32 * @bqt: the tag map to free
33 *
34 * Drop the reference count on @bqt and frees it when the last reference
35 * is dropped.
36 */
blk_free_tags(struct blk_queue_tag * bqt)37 void blk_free_tags(struct blk_queue_tag *bqt)
38 {
39 if (atomic_dec_and_test(&bqt->refcnt)) {
40 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
41 bqt->max_depth);
42
43 kfree(bqt->tag_index);
44 bqt->tag_index = NULL;
45
46 kfree(bqt->tag_map);
47 bqt->tag_map = NULL;
48
49 kfree(bqt);
50 }
51 }
52 EXPORT_SYMBOL(blk_free_tags);
53
54 /**
55 * __blk_queue_free_tags - release tag maintenance info
56 * @q: the request queue for the device
57 *
58 * Notes:
59 * blk_cleanup_queue() will take care of calling this function, if tagging
60 * has been used. So there's no need to call this directly.
61 **/
__blk_queue_free_tags(struct request_queue * q)62 void __blk_queue_free_tags(struct request_queue *q)
63 {
64 struct blk_queue_tag *bqt = q->queue_tags;
65
66 if (!bqt)
67 return;
68
69 blk_free_tags(bqt);
70
71 q->queue_tags = NULL;
72 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
73 }
74
75 /**
76 * blk_queue_free_tags - release tag maintenance info
77 * @q: the request queue for the device
78 *
79 * Notes:
80 * This is used to disable tagged queuing to a device, yet leave
81 * queue in function.
82 **/
blk_queue_free_tags(struct request_queue * q)83 void blk_queue_free_tags(struct request_queue *q)
84 {
85 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
86 }
87 EXPORT_SYMBOL(blk_queue_free_tags);
88
89 static int
init_tag_map(struct request_queue * q,struct blk_queue_tag * tags,int depth)90 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
91 {
92 struct request **tag_index;
93 unsigned long *tag_map;
94 int nr_ulongs;
95
96 if (q && depth > q->nr_requests * 2) {
97 depth = q->nr_requests * 2;
98 printk(KERN_ERR "%s: adjusted depth to %d\n",
99 __func__, depth);
100 }
101
102 tag_index = kcalloc(depth, sizeof(struct request *), GFP_ATOMIC);
103 if (!tag_index)
104 goto fail;
105
106 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
107 tag_map = kcalloc(nr_ulongs, sizeof(unsigned long), GFP_ATOMIC);
108 if (!tag_map)
109 goto fail;
110
111 tags->real_max_depth = depth;
112 tags->max_depth = depth;
113 tags->tag_index = tag_index;
114 tags->tag_map = tag_map;
115
116 return 0;
117 fail:
118 kfree(tag_index);
119 return -ENOMEM;
120 }
121
__blk_queue_init_tags(struct request_queue * q,int depth,int alloc_policy)122 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
123 int depth, int alloc_policy)
124 {
125 struct blk_queue_tag *tags;
126
127 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
128 if (!tags)
129 goto fail;
130
131 if (init_tag_map(q, tags, depth))
132 goto fail;
133
134 atomic_set(&tags->refcnt, 1);
135 tags->alloc_policy = alloc_policy;
136 tags->next_tag = 0;
137 return tags;
138 fail:
139 kfree(tags);
140 return NULL;
141 }
142
143 /**
144 * blk_init_tags - initialize the tag info for an external tag map
145 * @depth: the maximum queue depth supported
146 * @alloc_policy: tag allocation policy
147 **/
blk_init_tags(int depth,int alloc_policy)148 struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy)
149 {
150 return __blk_queue_init_tags(NULL, depth, alloc_policy);
151 }
152 EXPORT_SYMBOL(blk_init_tags);
153
154 /**
155 * blk_queue_init_tags - initialize the queue tag info
156 * @q: the request queue for the device
157 * @depth: the maximum queue depth supported
158 * @tags: the tag to use
159 * @alloc_policy: tag allocation policy
160 *
161 * Queue lock must be held here if the function is called to resize an
162 * existing map.
163 **/
blk_queue_init_tags(struct request_queue * q,int depth,struct blk_queue_tag * tags,int alloc_policy)164 int blk_queue_init_tags(struct request_queue *q, int depth,
165 struct blk_queue_tag *tags, int alloc_policy)
166 {
167 int rc;
168
169 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
170
171 if (!tags && !q->queue_tags) {
172 tags = __blk_queue_init_tags(q, depth, alloc_policy);
173
174 if (!tags)
175 return -ENOMEM;
176
177 } else if (q->queue_tags) {
178 rc = blk_queue_resize_tags(q, depth);
179 if (rc)
180 return rc;
181 queue_flag_set(QUEUE_FLAG_QUEUED, q);
182 return 0;
183 } else
184 atomic_inc(&tags->refcnt);
185
186 /*
187 * assign it, all done
188 */
189 q->queue_tags = tags;
190 queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
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 **/
blk_queue_resize_tags(struct request_queue * q,int new_depth)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 **/
blk_queue_end_tag(struct request_queue * q,struct request * rq)262 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
263 {
264 struct blk_queue_tag *bqt = q->queue_tags;
265 unsigned tag = rq->tag; /* negative tags invalid */
266
267 lockdep_assert_held(q->queue_lock);
268
269 BUG_ON(tag >= bqt->real_max_depth);
270
271 list_del_init(&rq->queuelist);
272 rq->rq_flags &= ~RQF_QUEUED;
273 rq->tag = -1;
274 rq->internal_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
294 /**
295 * blk_queue_start_tag - find a free tag and assign it
296 * @q: the request queue for the device
297 * @rq: the block request that needs tagging
298 *
299 * Description:
300 * This can either be used as a stand-alone helper, or possibly be
301 * assigned as the queue &prep_rq_fn (in which case &struct request
302 * automagically gets a tag assigned). Note that this function
303 * assumes that any type of request can be queued! if this is not
304 * true for your device, you must check the request type before
305 * calling this function. The request will also be removed from
306 * the request queue, so it's the drivers responsibility to readd
307 * it if it should need to be restarted for some reason.
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 lockdep_assert_held(q->queue_lock);
316
317 if (unlikely((rq->rq_flags & RQF_QUEUED))) {
318 printk(KERN_ERR
319 "%s: request %p for device [%s] already tagged %d",
320 __func__, rq,
321 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
322 BUG();
323 }
324
325 /*
326 * Protect against shared tag maps, as we may not have exclusive
327 * access to the tag map.
328 *
329 * We reserve a few tags just for sync IO, since we don't want
330 * to starve sync IO on behalf of flooding async IO.
331 */
332 max_depth = bqt->max_depth;
333 if (!rq_is_sync(rq) && max_depth > 1) {
334 switch (max_depth) {
335 case 2:
336 max_depth = 1;
337 break;
338 case 3:
339 max_depth = 2;
340 break;
341 default:
342 max_depth -= 2;
343 }
344 if (q->in_flight[BLK_RW_ASYNC] > max_depth)
345 return 1;
346 }
347
348 do {
349 if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) {
350 tag = find_first_zero_bit(bqt->tag_map, max_depth);
351 if (tag >= max_depth)
352 return 1;
353 } else {
354 int start = bqt->next_tag;
355 int size = min_t(int, bqt->max_depth, max_depth + start);
356 tag = find_next_zero_bit(bqt->tag_map, size, start);
357 if (tag >= size && start + size > bqt->max_depth) {
358 size = start + size - bqt->max_depth;
359 tag = find_first_zero_bit(bqt->tag_map, size);
360 }
361 if (tag >= size)
362 return 1;
363 }
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 bqt->next_tag = (tag + 1) % bqt->max_depth;
372 rq->rq_flags |= RQF_QUEUED;
373 rq->tag = tag;
374 bqt->tag_index[tag] = rq;
375 blk_start_request(rq);
376 return 0;
377 }
378 EXPORT_SYMBOL(blk_queue_start_tag);
379
