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
   9 #include "blk.h"
  10
  11 /**
  12  * blk_queue_find_tag - find a request by its tag and queue
  13  * @q:   The request queue for the device
  14  * @tag: The tag of the request
  15  *
  16  * Notes:
  17  *    Should be used when a device returns a tag and you want to match
  18  *    it with a request.
  19  *
  20  *    no locks need be held.
  21  **/
  22 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
  23 {
  24         return blk_map_queue_find_tag(q->queue_tags, tag);
  25 }
  26 EXPORT_SYMBOL(blk_queue_find_tag);
  27
  28 /**
  29  * __blk_free_tags - release a given set of tag maintenance info
  30  * @bqt:        the tag map to free
  31  *
  32  * Tries to free the specified @bqt@.  Returns true if it was
  33  * actually freed and false if there are still references using it
  34  */
  35 static int __blk_free_tags(struct blk_queue_tag *bqt)
  36 {
  37         int retval;
  38
  39         retval = atomic_dec_and_test(&bqt->refcnt);
  40         if (retval) {
  41                 BUG_ON(bqt->busy);
  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         return retval;
  53 }
  54
  55 /**
  56  * __blk_queue_free_tags - release tag maintenance info
  57  * @q:  the request queue for the device
  58  *
  59  *  Notes:
  60  *    blk_cleanup_queue() will take care of calling this function, if tagging
  61  *    has been used. So there's no need to call this directly.
  62  **/
  63 void __blk_queue_free_tags(struct request_queue *q)
  64 {
  65         struct blk_queue_tag *bqt = q->queue_tags;
  66
  67         if (!bqt)
  68                 return;
  69
  70         __blk_free_tags(bqt);
  71
  72         q->queue_tags = NULL;
  73         q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
  74 }
  75
  76 /**
  77  * blk_free_tags - release a given set of tag maintenance info
  78  * @bqt:        the tag map to free
  79  *
  80  * For externally managed @bqt@ frees the map.  Callers of this
  81  * function must guarantee to have released all the queues that
  82  * might have been using this tag map.
  83  */
  84 void blk_free_tags(struct blk_queue_tag *bqt)
  85 {
  86         if (unlikely(!__blk_free_tags(bqt)))
  87                 BUG();
  88 }
  89 EXPORT_SYMBOL(blk_free_tags);
  90
  91 /**
  92  * blk_queue_free_tags - release tag maintenance info
  93  * @q:  the request queue for the device
  94  *
  95  *  Notes:
  96  *      This is used to disabled tagged queuing to a device, yet leave
  97  *      queue in function.
  98  **/
  99 void blk_queue_free_tags(struct request_queue *q)
 100 {
 101         clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
 102 }
 103 EXPORT_SYMBOL(blk_queue_free_tags);
 104
 105 static int
 106 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
 107 {
 108         struct request **tag_index;
 109         unsigned long *tag_map;
 110         int nr_ulongs;
 111
 112         if (q && depth > q->nr_requests * 2) {
 113                 depth = q->nr_requests * 2;
 114                 printk(KERN_ERR "%s: adjusted depth to %d\n",
 115                                 __FUNCTION__, depth);
 116         }
 117
 118         tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
 119         if (!tag_index)
 120                 goto fail;
 121
 122         nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
 123         tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
 124         if (!tag_map)
 125                 goto fail;
 126
 127         tags->real_max_depth = depth;
 128         tags->max_depth = depth;
 129         tags->tag_index = tag_index;
 130         tags->tag_map = tag_map;
 131
 132         return 0;
 133 fail:
 134         kfree(tag_index);
 135         return -ENOMEM;
 136 }
 137
 138 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
 139                                                    int depth)
 140 {
 141         struct blk_queue_tag *tags;
 142
 143         tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
 144         if (!tags)
 145                 goto fail;
 146
 147         if (init_tag_map(q, tags, depth))
 148                 goto fail;
 149
 150         tags->busy = 0;
 151         atomic_set(&tags->refcnt, 1);
 152         return tags;
 153 fail:
 154         kfree(tags);
 155         return NULL;
 156 }
 157
 158 /**
 159  * blk_init_tags - initialize the tag info for an external tag map
 160  * @depth:      the maximum queue depth supported
 161  * @tags: the tag to use
 162  **/
 163 struct blk_queue_tag *blk_init_tags(int depth)
 164 {
 165         return __blk_queue_init_tags(NULL, depth);
 166 }
 167 EXPORT_SYMBOL(blk_init_tags);
 168
 169 /**
 170  * blk_queue_init_tags - initialize the queue tag info
 171  * @q:  the request queue for the device
 172  * @depth:  the maximum queue depth supported
 173  * @tags: the tag to use
 174  **/
 175 int blk_queue_init_tags(struct request_queue *q, int depth,
 176                         struct blk_queue_tag *tags)
 177 {
 178         int rc;
 179
 180         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
 181
 182         if (!tags && !q->queue_tags) {
 183                 tags = __blk_queue_init_tags(q, depth);
 184
 185                 if (!tags)
 186                         goto fail;
 187         } else if (q->queue_tags) {
 188                 rc = blk_queue_resize_tags(q, depth);
 189                 if (rc)
 190                         return rc;
 191                 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
 192                 return 0;
 193         } else
 194                 atomic_inc(&tags->refcnt);
 195
 196         /*
 197          * assign it, all done
 198          */
 199         q->queue_tags = tags;
 200         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
 201         INIT_LIST_HEAD(&q->tag_busy_list);
 202         return 0;
 203 fail:
 204         kfree(tags);
 205         return -ENOMEM;
 206 }
 207 EXPORT_SYMBOL(blk_queue_init_tags);
 208
 209 /**
 210  * blk_queue_resize_tags - change the queueing depth
 211  * @q:  the request queue for the device
 212  * @new_depth: the new max command queueing depth
 213  *
 214  *  Notes:
 215  *    Must be called with the queue lock held.
 216  **/
 217 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
 218 {
 219         struct blk_queue_tag *bqt = q->queue_tags;
 220         struct request **tag_index;
 221         unsigned long *tag_map;
 222         int max_depth, nr_ulongs;
 223
 224         if (!bqt)
 225                 return -ENXIO;
 226
 227         /*
 228          * if we already have large enough real_max_depth.  just
 229          * adjust max_depth.  *NOTE* as requests with tag value
 230          * between new_depth and real_max_depth can be in-flight, tag
 231          * map can not be shrunk blindly here.
 232          */
 233         if (new_depth <= bqt->real_max_depth) {
 234                 bqt->max_depth = new_depth;
 235                 return 0;
 236         }
 237
 238         /*
 239          * Currently cannot replace a shared tag map with a new
 240          * one, so error out if this is the case
 241          */
 242         if (atomic_read(&bqt->refcnt) != 1)
 243                 return -EBUSY;
 244
 245         /*
 246          * save the old state info, so we can copy it back
 247          */
 248         tag_index = bqt->tag_index;
 249         tag_map = bqt->tag_map;
 250         max_depth = bqt->real_max_depth;
 251
 252         if (init_tag_map(q, bqt, new_depth))
 253                 return -ENOMEM;
 254
 255         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 256         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 257         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
 258
 259         kfree(tag_index);
 260         kfree(tag_map);
 261         return 0;
 262 }
 263 EXPORT_SYMBOL(blk_queue_resize_tags);
 264
 265 /**
 266  * blk_queue_end_tag - end tag operations for a request
 267  * @q:  the request queue for the device
 268  * @rq: the request that has completed
 269  *
 270  *  Description:
 271  *    Typically called when end_that_request_first() returns 0, meaning
 272  *    all transfers have been done for a request. It's important to call
 273  *    this function before end_that_request_last(), as that will put the
 274  *    request back on the free list thus corrupting the internal tag list.
 275  *
 276  *  Notes:
 277  *   queue lock must be held.
 278  **/
 279 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 280 {
 281         struct blk_queue_tag *bqt = q->queue_tags;
 282         int tag = rq->tag;
 283
 284         BUG_ON(tag == -1);
 285
 286         if (unlikely(tag >= bqt->real_max_depth))
 287                 /*
 288                  * This can happen after tag depth has been reduced.
 289                  * FIXME: how about a warning or info message here?
 290                  */
 291                 return;
 292
 293         list_del_init(&rq->queuelist);
 294         rq->cmd_flags &= ~REQ_QUEUED;
 295         rq->tag = -1;
 296
 297         if (unlikely(bqt->tag_index[tag] == NULL))
 298                 printk(KERN_ERR "%s: tag %d is missing\n",
 299                        __FUNCTION__, tag);
 300
 301         bqt->tag_index[tag] = NULL;
 302
 303         if (unlikely(!test_bit(tag, bqt->tag_map))) {
 304                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 305                        __FUNCTION__, tag);
 306                 return;
 307         }
 308         /*
 309          * The tag_map bit acts as a lock for tag_index[bit], so we need
 310          * unlock memory barrier semantics.
 311          */
 312         clear_bit_unlock(tag, bqt->tag_map);
 313         bqt->busy--;
 314 }
 315 EXPORT_SYMBOL(blk_queue_end_tag);
 316
 317 /**
 318  * blk_queue_start_tag - find a free tag and assign it
 319  * @q:  the request queue for the device
 320  * @rq:  the block request that needs tagging
 321  *
 322  *  Description:
 323  *    This can either be used as a stand-alone helper, or possibly be
 324  *    assigned as the queue &prep_rq_fn (in which case &struct request
 325  *    automagically gets a tag assigned). Note that this function
 326  *    assumes that any type of request can be queued! if this is not
 327  *    true for your device, you must check the request type before
 328  *    calling this function.  The request will also be removed from
 329  *    the request queue, so it's the drivers responsibility to readd
 330  *    it if it should need to be restarted for some reason.
 331  *
 332  *  Notes:
 333  *   queue lock must be held.
 334  **/
 335 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 336 {
 337         struct blk_queue_tag *bqt = q->queue_tags;
 338         int tag;
 339
 340         if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 341                 printk(KERN_ERR
 342                        "%s: request %p for device [%s] already tagged %d",
 343                        __FUNCTION__, rq,
 344                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 345                 BUG();
 346         }
 347
 348         /*
 349          * Protect against shared tag maps, as we may not have exclusive
 350          * access to the tag map.
 351          */
 352         do {
 353                 tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
 354                 if (tag >= bqt->max_depth)
 355                         return 1;
 356
 357         } while (test_and_set_bit_lock(tag, bqt->tag_map));
 358         /*
 359          * We need lock ordering semantics given by test_and_set_bit_lock.
 360          * See blk_queue_end_tag for details.
 361          */
 362
 363         rq->cmd_flags |= REQ_QUEUED;
 364         rq->tag = tag;
 365         bqt->tag_index[tag] = rq;
 366         blkdev_dequeue_request(rq);
 367         list_add(&rq->queuelist, &q->tag_busy_list);
 368         bqt->busy++;
 369         return 0;
 370 }
 371 EXPORT_SYMBOL(blk_queue_start_tag);
 372
 373 /**
 374  * blk_queue_invalidate_tags - invalidate all pending tags
 375  * @q:  the request queue for the device
 376  *
 377  *  Description:
 378  *   Hardware conditions may dictate a need to stop all pending requests.
 379  *   In this case, we will safely clear the block side of the tag queue and
 380  *   readd all requests to the request queue in the right order.
 381  *
 382  *  Notes:
 383  *   queue lock must be held.
 384  **/
 385 void blk_queue_invalidate_tags(struct request_queue *q)
 386 {
 387         struct list_head *tmp, *n;
 388
 389         list_for_each_safe(tmp, n, &q->tag_busy_list)
 390                 blk_requeue_request(q, list_entry_rq(tmp));
 391 }
 392 EXPORT_SYMBOL(blk_queue_invalidate_tags);