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)
 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                         goto fail;
 171         } else if (q->queue_tags) {
 172                 rc = blk_queue_resize_tags(q, depth);
 173                 if (rc)
 174                         return rc;
 175                 queue_flag_set(QUEUE_FLAG_QUEUED, q);
 176                 return 0;
 177         } else
 178                 atomic_inc(&tags->refcnt);
 179
 180         /*
 181          * assign it, all done
 182          */
 183         q->queue_tags = tags;
 184         queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
 185         INIT_LIST_HEAD(&q->tag_busy_list);
 186         return 0;
 187 fail:
 188         kfree(tags);
 189         return -ENOMEM;
 190 }
 191 EXPORT_SYMBOL(blk_queue_init_tags);
 192
 193 /**
 194  * blk_queue_resize_tags - change the queueing depth
 195  * @q:  the request queue for the device
 196  * @new_depth: the new max command queueing depth
 197  *
 198  *  Notes:
 199  *    Must be called with the queue lock held.
 200  **/
 201 int blk_queue_resize_tags(struct request_queue *q, int new_depth)
 202 {
 203         struct blk_queue_tag *bqt = q->queue_tags;
 204         struct request **tag_index;
 205         unsigned long *tag_map;
 206         int max_depth, nr_ulongs;
 207
 208         if (!bqt)
 209                 return -ENXIO;
 210
 211         /*
 212          * if we already have large enough real_max_depth.  just
 213          * adjust max_depth.  *NOTE* as requests with tag value
 214          * between new_depth and real_max_depth can be in-flight, tag
 215          * map can not be shrunk blindly here.
 216          */
 217         if (new_depth <= bqt->real_max_depth) {
 218                 bqt->max_depth = new_depth;
 219                 return 0;
 220         }
 221
 222         /*
 223          * Currently cannot replace a shared tag map with a new
 224          * one, so error out if this is the case
 225          */
 226         if (atomic_read(&bqt->refcnt) != 1)
 227                 return -EBUSY;
 228
 229         /*
 230          * save the old state info, so we can copy it back
 231          */
 232         tag_index = bqt->tag_index;
 233         tag_map = bqt->tag_map;
 234         max_depth = bqt->real_max_depth;
 235
 236         if (init_tag_map(q, bqt, new_depth))
 237                 return -ENOMEM;
 238
 239         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 240         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 241         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
 242
 243         kfree(tag_index);
 244         kfree(tag_map);
 245         return 0;
 246 }
 247 EXPORT_SYMBOL(blk_queue_resize_tags);
 248
 249 /**
 250  * blk_queue_end_tag - end tag operations for a request
 251  * @q:  the request queue for the device
 252  * @rq: the request that has completed
 253  *
 254  *  Description:
 255  *    Typically called when end_that_request_first() returns %0, meaning
 256  *    all transfers have been done for a request. It's important to call
 257  *    this function before end_that_request_last(), as that will put the
 258  *    request back on the free list thus corrupting the internal tag list.
 259  *
 260  *  Notes:
 261  *   queue lock must be held.
 262  **/
 263 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 264 {
 265         struct blk_queue_tag *bqt = q->queue_tags;
 266         unsigned tag = rq->tag; /* negative tags invalid */
 267
 268         BUG_ON(tag >= bqt->real_max_depth);
 269
 270         list_del_init(&rq->queuelist);
 271         rq->cmd_flags &= ~REQ_QUEUED;
 272         rq->tag = -1;
 273
 274         if (unlikely(bqt->tag_index[tag] == NULL))
 275                 printk(KERN_ERR "%s: tag %d is missing\n",
 276                        __func__, tag);
 277
 278         bqt->tag_index[tag] = NULL;
 279
 280         if (unlikely(!test_bit(tag, bqt->tag_map))) {
 281                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 282                        __func__, tag);
 283                 return;
 284         }
 285         /*
 286          * The tag_map bit acts as a lock for tag_index[bit], so we need
 287          * unlock memory barrier semantics.
 288          */
 289         clear_bit_unlock(tag, bqt->tag_map);
 290 }
 291 EXPORT_SYMBOL(blk_queue_end_tag);
 292
 293 /**
 294  * blk_queue_start_tag - find a free tag and assign it
 295  * @q:  the request queue for the device
 296  * @rq:  the block request that needs tagging
 297  *
 298  *  Description:
 299  *    This can either be used as a stand-alone helper, or possibly be
 300  *    assigned as the queue &prep_rq_fn (in which case &struct request
 301  *    automagically gets a tag assigned). Note that this function
 302  *    assumes that any type of request can be queued! if this is not
 303  *    true for your device, you must check the request type before
 304  *    calling this function.  The request will also be removed from
 305  *    the request queue, so it's the drivers responsibility to readd
 306  *    it if it should need to be restarted for some reason.
 307  *
 308  *  Notes:
 309  *   queue lock must be held.
 310  **/
 311 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 312 {
 313         struct blk_queue_tag *bqt = q->queue_tags;
 314         unsigned max_depth;
 315         int tag;
 316
 317         if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 318                 printk(KERN_ERR
 319                        "%s: request %p for device [%s] already tagged %d",
 320                        __func__, rq,
 321                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 322                 BUG();
 323         }
 324
 325         /*
 326          * Protect against shared tag maps, as we may not have exclusive
 327          * access to the tag map.
 328          *
 329          * We reserve a few tags just for sync IO, since we don't want
 330          * to starve sync IO on behalf of flooding async IO.
 331          */
 332         max_depth = bqt->max_depth;
 333         if (!rq_is_sync(rq) && max_depth > 1) {
 334                 max_depth -= 2;
 335                 if (!max_depth)
 336                         max_depth = 1;
 337                 if (q->in_flight[BLK_RW_ASYNC] > max_depth)
 338                         return 1;
 339         }
 340
 341         do {
 342                 tag = find_first_zero_bit(bqt->tag_map, max_depth);
 343                 if (tag >= max_depth)
 344                         return 1;
 345
 346         } while (test_and_set_bit_lock(tag, bqt->tag_map));
 347         /*
 348          * We need lock ordering semantics given by test_and_set_bit_lock.
 349          * See blk_queue_end_tag for details.
 350          */
 351
 352         rq->cmd_flags |= REQ_QUEUED;
 353         rq->tag = tag;
 354         bqt->tag_index[tag] = rq;
 355         blk_start_request(rq);
 356         list_add(&rq->queuelist, &q->tag_busy_list);
 357         return 0;
 358 }
 359 EXPORT_SYMBOL(blk_queue_start_tag);
 360
 361 /**
 362  * blk_queue_invalidate_tags - invalidate all pending tags
 363  * @q:  the request queue for the device
 364  *
 365  *  Description:
 366  *   Hardware conditions may dictate a need to stop all pending requests.
 367  *   In this case, we will safely clear the block side of the tag queue and
 368  *   readd all requests to the request queue in the right order.
 369  *
 370  *  Notes:
 371  *   queue lock must be held.
 372  **/
 373 void blk_queue_invalidate_tags(struct request_queue *q)
 374 {
 375         struct list_head *tmp, *n;
 376
 377         list_for_each_safe(tmp, n, &q->tag_busy_list)
 378                 blk_requeue_request(q, list_entry_rq(tmp));
 379 }
 380 EXPORT_SYMBOL(blk_queue_invalidate_tags);