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(find_first_bit(bqt->tag_map, bqt->max_depth) <
  42                                                         bqt->max_depth);
  43
  44                 kfree(bqt->tag_index);
  45                 bqt->tag_index = NULL;
  46
  47                 kfree(bqt->tag_map);
  48                 bqt->tag_map = NULL;
  49
  50                 kfree(bqt);
  51         }
  52
  53         return retval;
  54 }
  55
  56 /**
  57  * __blk_queue_free_tags - release tag maintenance info
  58  * @q:  the request queue for the device
  59  *
  60  *  Notes:
  61  *    blk_cleanup_queue() will take care of calling this function, if tagging
  62  *    has been used. So there's no need to call this directly.
  63  **/
  64 void __blk_queue_free_tags(struct request_queue *q)
  65 {
  66         struct blk_queue_tag *bqt = q->queue_tags;
  67
  68         if (!bqt)
  69                 return;
  70
  71         __blk_free_tags(bqt);
  72
  73         q->queue_tags = NULL;
  74         queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
  75 }
  76
  77 /**
  78  * blk_free_tags - release a given set of tag maintenance info
  79  * @bqt:        the tag map to free
  80  *
  81  * For externally managed @bqt frees the map.  Callers of this
  82  * function must guarantee to have released all the queues that
  83  * might have been using this tag map.
  84  */
  85 void blk_free_tags(struct blk_queue_tag *bqt)
  86 {
  87         if (unlikely(!__blk_free_tags(bqt)))
  88                 BUG();
  89 }
  90 EXPORT_SYMBOL(blk_free_tags);
  91
  92 /**
  93  * blk_queue_free_tags - release tag maintenance info
  94  * @q:  the request queue for the device
  95  *
  96  *  Notes:
  97  *      This is used to disable tagged queuing to a device, yet leave
  98  *      queue in function.
  99  **/
 100 void blk_queue_free_tags(struct request_queue *q)
 101 {
 102         queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
 103 }
 104 EXPORT_SYMBOL(blk_queue_free_tags);
 105
 106 static int
 107 init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
 108 {
 109         struct request **tag_index;
 110         unsigned long *tag_map;
 111         int nr_ulongs;
 112
 113         if (q && depth > q->nr_requests * 2) {
 114                 depth = q->nr_requests * 2;
 115                 printk(KERN_ERR "%s: adjusted depth to %d\n",
 116                        __func__, depth);
 117         }
 118
 119         tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
 120         if (!tag_index)
 121                 goto fail;
 122
 123         nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
 124         tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
 125         if (!tag_map)
 126                 goto fail;
 127
 128         tags->real_max_depth = depth;
 129         tags->max_depth = depth;
 130         tags->tag_index = tag_index;
 131         tags->tag_map = tag_map;
 132
 133         return 0;
 134 fail:
 135         kfree(tag_index);
 136         return -ENOMEM;
 137 }
 138
 139 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
 140                                                    int depth)
 141 {
 142         struct blk_queue_tag *tags;
 143
 144         tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
 145         if (!tags)
 146                 goto fail;
 147
 148         if (init_tag_map(q, tags, depth))
 149                 goto fail;
 150
 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  **/
 162 struct blk_queue_tag *blk_init_tags(int depth)
 163 {
 164         return __blk_queue_init_tags(NULL, depth);
 165 }
 166 EXPORT_SYMBOL(blk_init_tags);
 167
 168 /**
 169  * blk_queue_init_tags - initialize the queue tag info
 170  * @q:  the request queue for the device
 171  * @depth:  the maximum queue depth supported
 172  * @tags: the tag to use
 173  *
 174  * Queue lock must be held here if the function is called to resize an
 175  * existing map.
 176  **/
 177 int blk_queue_init_tags(struct request_queue *q, int depth,
 178                         struct blk_queue_tag *tags)
 179 {
 180         int rc;
 181
 182         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
 183
 184         if (!tags && !q->queue_tags) {
 185                 tags = __blk_queue_init_tags(q, depth);
 186
 187                 if (!tags)
 188                         goto fail;
 189         } else if (q->queue_tags) {
 190                 rc = blk_queue_resize_tags(q, depth);
 191                 if (rc)
 192                         return rc;
 193                 queue_flag_set(QUEUE_FLAG_QUEUED, q);
 194                 return 0;
 195         } else
 196                 atomic_inc(&tags->refcnt);
 197
 198         /*
 199          * assign it, all done
 200          */
 201         q->queue_tags = tags;
 202         queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
 203         INIT_LIST_HEAD(&q->tag_busy_list);
 204         return 0;
 205 fail:
 206         kfree(tags);
 207         return -ENOMEM;
 208 }
 209 EXPORT_SYMBOL(blk_queue_init_tags);
 210
 211 /**
 212  * blk_queue_resize_tags - change the queueing depth
 213  * @q:  the request queue for the device
 214  * @new_depth: the new max command queueing depth
 215  *
 216  *  Notes:
 217  *    Must be called with the queue lock held.
 218  **/
 219 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
 220 {
 221         struct blk_queue_tag *bqt = q->queue_tags;
 222         struct request **tag_index;
 223         unsigned long *tag_map;
 224         int max_depth, nr_ulongs;
 225
 226         if (!bqt)
 227                 return -ENXIO;
 228
 229         /*
 230          * if we already have large enough real_max_depth.  just
 231          * adjust max_depth.  *NOTE* as requests with tag value
 232          * between new_depth and real_max_depth can be in-flight, tag
 233          * map can not be shrunk blindly here.
 234          */
 235         if (new_depth <= bqt->real_max_depth) {
 236                 bqt->max_depth = new_depth;
 237                 return 0;
 238         }
 239
 240         /*
 241          * Currently cannot replace a shared tag map with a new
 242          * one, so error out if this is the case
 243          */
 244         if (atomic_read(&bqt->refcnt) != 1)
 245                 return -EBUSY;
 246
 247         /*
 248          * save the old state info, so we can copy it back
 249          */
 250         tag_index = bqt->tag_index;
 251         tag_map = bqt->tag_map;
 252         max_depth = bqt->real_max_depth;
 253
 254         if (init_tag_map(q, bqt, new_depth))
 255                 return -ENOMEM;
 256
 257         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 258         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 259         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
 260
 261         kfree(tag_index);
 262         kfree(tag_map);
 263         return 0;
 264 }
 265 EXPORT_SYMBOL(blk_queue_resize_tags);
 266
 267 /**
 268  * blk_queue_end_tag - end tag operations for a request
 269  * @q:  the request queue for the device
 270  * @rq: the request that has completed
 271  *
 272  *  Description:
 273  *    Typically called when end_that_request_first() returns %0, meaning
 274  *    all transfers have been done for a request. It's important to call
 275  *    this function before end_that_request_last(), as that will put the
 276  *    request back on the free list thus corrupting the internal tag list.
 277  *
 278  *  Notes:
 279  *   queue lock must be held.
 280  **/
 281 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 282 {
 283         struct blk_queue_tag *bqt = q->queue_tags;
 284         int tag = rq->tag;
 285
 286         BUG_ON(tag == -1);
 287
 288         if (unlikely(tag >= bqt->real_max_depth))
 289                 /*
 290                  * This can happen after tag depth has been reduced.
 291                  * FIXME: how about a warning or info message here?
 292                  */
 293                 return;
 294
 295         list_del_init(&rq->queuelist);
 296         rq->cmd_flags &= ~REQ_QUEUED;
 297         rq->tag = -1;
 298
 299         if (unlikely(bqt->tag_index[tag] == NULL))
 300                 printk(KERN_ERR "%s: tag %d is missing\n",
 301                        __func__, tag);
 302
 303         bqt->tag_index[tag] = NULL;
 304
 305         if (unlikely(!test_bit(tag, bqt->tag_map))) {
 306                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 307                        __func__, tag);
 308                 return;
 309         }
 310         /*
 311          * The tag_map bit acts as a lock for tag_index[bit], so we need
 312          * unlock memory barrier semantics.
 313          */
 314         clear_bit_unlock(tag, bqt->tag_map);
 315 }
 316 EXPORT_SYMBOL(blk_queue_end_tag);
 317
 318 /**
 319  * blk_queue_start_tag - find a free tag and assign it
 320  * @q:  the request queue for the device
 321  * @rq:  the block request that needs tagging
 322  *
 323  *  Description:
 324  *    This can either be used as a stand-alone helper, or possibly be
 325  *    assigned as the queue &prep_rq_fn (in which case &struct request
 326  *    automagically gets a tag assigned). Note that this function
 327  *    assumes that any type of request can be queued! if this is not
 328  *    true for your device, you must check the request type before
 329  *    calling this function.  The request will also be removed from
 330  *    the request queue, so it's the drivers responsibility to readd
 331  *    it if it should need to be restarted for some reason.
 332  *
 333  *  Notes:
 334  *   queue lock must be held.
 335  **/
 336 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 337 {
 338         struct blk_queue_tag *bqt = q->queue_tags;
 339         unsigned max_depth;
 340         int tag;
 341
 342         if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 343                 printk(KERN_ERR
 344                        "%s: request %p for device [%s] already tagged %d",
 345                        __func__, rq,
 346                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 347                 BUG();
 348         }
 349
 350         /*
 351          * Protect against shared tag maps, as we may not have exclusive
 352          * access to the tag map.
 353          *
 354          * We reserve a few tags just for sync IO, since we don't want
 355          * to starve sync IO on behalf of flooding async IO.
 356          */
 357         max_depth = bqt->max_depth;
 358         if (!rq_is_sync(rq) && max_depth > 1) {
 359                 max_depth -= 2;
 360                 if (!max_depth)
 361                         max_depth = 1;
 362                 if (q->in_flight[0] > max_depth)
 363                         return 1;
 364         }
 365
 366         do {
 367                 tag = find_first_zero_bit(bqt->tag_map, max_depth);
 368                 if (tag >= max_depth)
 369                         return 1;
 370
 371         } while (test_and_set_bit_lock(tag, bqt->tag_map));
 372         /*
 373          * We need lock ordering semantics given by test_and_set_bit_lock.
 374          * See blk_queue_end_tag for details.
 375          */
 376
 377         rq->cmd_flags |= REQ_QUEUED;
 378         rq->tag = tag;
 379         bqt->tag_index[tag] = rq;
 380         blk_start_request(rq);
 381         list_add(&rq->queuelist, &q->tag_busy_list);
 382         return 0;
 383 }
 384 EXPORT_SYMBOL(blk_queue_start_tag);
 385
 386 /**
 387  * blk_queue_invalidate_tags - invalidate all pending tags
 388  * @q:  the request queue for the device
 389  *
 390  *  Description:
 391  *   Hardware conditions may dictate a need to stop all pending requests.
 392  *   In this case, we will safely clear the block side of the tag queue and
 393  *   readd all requests to the request queue in the right order.
 394  *
 395  *  Notes:
 396  *   queue lock must be held.
 397  **/
 398 void blk_queue_invalidate_tags(struct request_queue *q)
 399 {
 400         struct list_head *tmp, *n;
 401
 402         list_for_each_safe(tmp, n, &q->tag_busy_list)
 403                 blk_requeue_request(q, list_entry_rq(tmp));
 404 }
 405 EXPORT_SYMBOL(blk_queue_invalidate_tags);