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 /**
  10  * blk_queue_find_tag - find a request by its tag and queue
  11  * @q:   The request queue for the device
  12  * @tag: The tag of the request
  13  *
  14  * Notes:
  15  *    Should be used when a device returns a tag and you want to match
  16  *    it with a request.
  17  *
  18  *    no locks need be held.
  19  **/
  20 struct request *blk_queue_find_tag(struct request_queue *q, int tag)
  21 {
  22         return blk_map_queue_find_tag(q->queue_tags, tag);
  23 }
  24 EXPORT_SYMBOL(blk_queue_find_tag);
  25
  26 /**
  27  * __blk_free_tags - release a given set of tag maintenance info
  28  * @bqt:        the tag map to free
  29  *
  30  * Tries to free the specified @bqt@.  Returns true if it was
  31  * actually freed and false if there are still references using it
  32  */
  33 static int __blk_free_tags(struct blk_queue_tag *bqt)
  34 {
  35         int retval;
  36
  37         retval = atomic_dec_and_test(&bqt->refcnt);
  38         if (retval) {
  39                 BUG_ON(bqt->busy);
  40
  41                 kfree(bqt->tag_index);
  42                 bqt->tag_index = NULL;
  43
  44                 kfree(bqt->tag_map);
  45                 bqt->tag_map = NULL;
  46
  47                 kfree(bqt);
  48         }
  49
  50         return retval;
  51 }
  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         q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
  72 }
  73
  74 /**
  75  * blk_free_tags - release a given set of tag maintenance info
  76  * @bqt:        the tag map to free
  77  *
  78  * For externally managed @bqt@ frees the map.  Callers of this
  79  * function must guarantee to have released all the queues that
  80  * might have been using this tag map.
  81  */
  82 void blk_free_tags(struct blk_queue_tag *bqt)
  83 {
  84         if (unlikely(!__blk_free_tags(bqt)))
  85                 BUG();
  86 }
  87 EXPORT_SYMBOL(blk_free_tags);
  88
  89 /**
  90  * blk_queue_free_tags - release tag maintenance info
  91  * @q:  the request queue for the device
  92  *
  93  *  Notes:
  94  *      This is used to disabled tagged queuing to a device, yet leave
  95  *      queue in function.
  96  **/
  97 void blk_queue_free_tags(struct request_queue *q)
  98 {
  99         clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
 100 }
 101 EXPORT_SYMBOL(blk_queue_free_tags);
 102
 103 static int
 104 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
 105 {
 106         struct request **tag_index;
 107         unsigned long *tag_map;
 108         int nr_ulongs;
 109
 110         if (q && depth > q->nr_requests * 2) {
 111                 depth = q->nr_requests * 2;
 112                 printk(KERN_ERR "%s: adjusted depth to %d\n",
 113                                 __FUNCTION__, depth);
 114         }
 115
 116         tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
 117         if (!tag_index)
 118                 goto fail;
 119
 120         nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
 121         tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
 122         if (!tag_map)
 123                 goto fail;
 124
 125         tags->real_max_depth = depth;
 126         tags->max_depth = depth;
 127         tags->tag_index = tag_index;
 128         tags->tag_map = tag_map;
 129
 130         return 0;
 131 fail:
 132         kfree(tag_index);
 133         return -ENOMEM;
 134 }
 135
 136 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
 137                                                    int depth)
 138 {
 139         struct blk_queue_tag *tags;
 140
 141         tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
 142         if (!tags)
 143                 goto fail;
 144
 145         if (init_tag_map(q, tags, depth))
 146                 goto fail;
 147
 148         tags->busy = 0;
 149         atomic_set(&tags->refcnt, 1);
 150         return tags;
 151 fail:
 152         kfree(tags);
 153         return NULL;
 154 }
 155
 156 /**
 157  * blk_init_tags - initialize the tag info for an external tag map
 158  * @depth:      the maximum queue depth supported
 159  * @tags: the tag to use
 160  **/
 161 struct blk_queue_tag *blk_init_tags(int depth)
 162 {
 163         return __blk_queue_init_tags(NULL, depth);
 164 }
 165 EXPORT_SYMBOL(blk_init_tags);
 166
 167 /**
 168  * blk_queue_init_tags - initialize the queue tag info
 169  * @q:  the request queue for the device
 170  * @depth:  the maximum queue depth supported
 171  * @tags: the tag to use
 172  **/
 173 int blk_queue_init_tags(struct request_queue *q, int depth,
 174                         struct blk_queue_tag *tags)
 175 {
 176         int rc;
 177
 178         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
 179
 180         if (!tags && !q->queue_tags) {
 181                 tags = __blk_queue_init_tags(q, depth);
 182
 183                 if (!tags)
 184                         goto fail;
 185         } else if (q->queue_tags) {
 186                 rc = blk_queue_resize_tags(q, depth);
 187                 if (rc)
 188                         return rc;
 189                 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
 190                 return 0;
 191         } else
 192                 atomic_inc(&tags->refcnt);
 193
 194         /*
 195          * assign it, all done
 196          */
 197         q->queue_tags = tags;
 198         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
 199         INIT_LIST_HEAD(&q->tag_busy_list);
 200         return 0;
 201 fail:
 202         kfree(tags);
 203         return -ENOMEM;
 204 }
 205 EXPORT_SYMBOL(blk_queue_init_tags);
 206
 207 /**
 208  * blk_queue_resize_tags - change the queueing depth
 209  * @q:  the request queue for the device
 210  * @new_depth: the new max command queueing depth
 211  *
 212  *  Notes:
 213  *    Must be called with the queue lock held.
 214  **/
 215 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
 216 {
 217         struct blk_queue_tag *bqt = q->queue_tags;
 218         struct request **tag_index;
 219         unsigned long *tag_map;
 220         int max_depth, nr_ulongs;
 221
 222         if (!bqt)
 223                 return -ENXIO;
 224
 225         /*
 226          * if we already have large enough real_max_depth.  just
 227          * adjust max_depth.  *NOTE* as requests with tag value
 228          * between new_depth and real_max_depth can be in-flight, tag
 229          * map can not be shrunk blindly here.
 230          */
 231         if (new_depth <= bqt->real_max_depth) {
 232                 bqt->max_depth = new_depth;
 233                 return 0;
 234         }
 235
 236         /*
 237          * Currently cannot replace a shared tag map with a new
 238          * one, so error out if this is the case
 239          */
 240         if (atomic_read(&bqt->refcnt) != 1)
 241                 return -EBUSY;
 242
 243         /*
 244          * save the old state info, so we can copy it back
 245          */
 246         tag_index = bqt->tag_index;
 247         tag_map = bqt->tag_map;
 248         max_depth = bqt->real_max_depth;
 249
 250         if (init_tag_map(q, bqt, new_depth))
 251                 return -ENOMEM;
 252
 253         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 254         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 255         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
 256
 257         kfree(tag_index);
 258         kfree(tag_map);
 259         return 0;
 260 }
 261 EXPORT_SYMBOL(blk_queue_resize_tags);
 262
 263 /**
 264  * blk_queue_end_tag - end tag operations for a request
 265  * @q:  the request queue for the device
 266  * @rq: the request that has completed
 267  *
 268  *  Description:
 269  *    Typically called when end_that_request_first() returns 0, meaning
 270  *    all transfers have been done for a request. It's important to call
 271  *    this function before end_that_request_last(), as that will put the
 272  *    request back on the free list thus corrupting the internal tag list.
 273  *
 274  *  Notes:
 275  *   queue lock must be held.
 276  **/
 277 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 278 {
 279         struct blk_queue_tag *bqt = q->queue_tags;
 280         int tag = rq->tag;
 281
 282         BUG_ON(tag == -1);
 283
 284         if (unlikely(tag >= bqt->real_max_depth))
 285                 /*
 286                  * This can happen after tag depth has been reduced.
 287                  * FIXME: how about a warning or info message here?
 288                  */
 289                 return;
 290
 291         list_del_init(&rq->queuelist);
 292         rq->cmd_flags &= ~REQ_QUEUED;
 293         rq->tag = -1;
 294
 295         if (unlikely(bqt->tag_index[tag] == NULL))
 296                 printk(KERN_ERR "%s: tag %d is missing\n",
 297                        __FUNCTION__, tag);
 298
 299         bqt->tag_index[tag] = NULL;
 300
 301         if (unlikely(!test_bit(tag, bqt->tag_map))) {
 302                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 303                        __FUNCTION__, tag);
 304                 return;
 305         }
 306         /*
 307          * The tag_map bit acts as a lock for tag_index[bit], so we need
 308          * unlock memory barrier semantics.
 309          */
 310         clear_bit_unlock(tag, bqt->tag_map);
 311         bqt->busy--;
 312 }
 313 EXPORT_SYMBOL(blk_queue_end_tag);
 314
 315 /**
 316  * blk_queue_start_tag - find a free tag and assign it
 317  * @q:  the request queue for the device
 318  * @rq:  the block request that needs tagging
 319  *
 320  *  Description:
 321  *    This can either be used as a stand-alone helper, or possibly be
 322  *    assigned as the queue &prep_rq_fn (in which case &struct request
 323  *    automagically gets a tag assigned). Note that this function
 324  *    assumes that any type of request can be queued! if this is not
 325  *    true for your device, you must check the request type before
 326  *    calling this function.  The request will also be removed from
 327  *    the request queue, so it's the drivers responsibility to readd
 328  *    it if it should need to be restarted for some reason.
 329  *
 330  *  Notes:
 331  *   queue lock must be held.
 332  **/
 333 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 334 {
 335         struct blk_queue_tag *bqt = q->queue_tags;
 336         int tag;
 337
 338         if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 339                 printk(KERN_ERR
 340                        "%s: request %p for device [%s] already tagged %d",
 341                        __FUNCTION__, rq,
 342                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 343                 BUG();
 344         }
 345
 346         /*
 347          * Protect against shared tag maps, as we may not have exclusive
 348          * access to the tag map.
 349          */
 350         do {
 351                 tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
 352                 if (tag >= bqt->max_depth)
 353                         return 1;
 354
 355         } while (test_and_set_bit_lock(tag, bqt->tag_map));
 356         /*
 357          * We need lock ordering semantics given by test_and_set_bit_lock.
 358          * See blk_queue_end_tag for details.
 359          */
 360
 361         rq->cmd_flags |= REQ_QUEUED;
 362         rq->tag = tag;
 363         bqt->tag_index[tag] = rq;
 364         blkdev_dequeue_request(rq);
 365         list_add(&rq->queuelist, &q->tag_busy_list);
 366         bqt->busy++;
 367         return 0;
 368 }
 369 EXPORT_SYMBOL(blk_queue_start_tag);
 370
 371 /**
 372  * blk_queue_invalidate_tags - invalidate all pending tags
 373  * @q:  the request queue for the device
 374  *
 375  *  Description:
 376  *   Hardware conditions may dictate a need to stop all pending requests.
 377  *   In this case, we will safely clear the block side of the tag queue and
 378  *   readd all requests to the request queue in the right order.
 379  *
 380  *  Notes:
 381  *   queue lock must be held.
 382  **/
 383 void blk_queue_invalidate_tags(struct request_queue *q)
 384 {
 385         struct list_head *tmp, *n;
 386
 387         list_for_each_safe(tmp, n, &q->tag_busy_list)
 388                 blk_requeue_request(q, list_entry_rq(tmp));
 389 }
 390 EXPORT_SYMBOL(blk_queue_invalidate_tags);