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TOMOYO Linux Cross Reference
Linux/block/blk-tag.c

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

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