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Linux/block/blk-tag.c

  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);
403 

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