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 **/
  23struct request *blk_queue_find_tag(struct request_queue *q, int tag)
  24{
  25        return blk_map_queue_find_tag(q->queue_tags, tag);
  26}
  27EXPORT_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 * Tries to free the specified @bqt.  Returns true if it was
  34 * actually freed and false if there are still references using it
  35 */
  36static int __blk_free_tags(struct blk_queue_tag *bqt)
  37{
  38        int retval;
  39
  40        retval = atomic_dec_and_test(&bqt->refcnt);
  41        if (retval) {
  42                BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
  43                                                        bqt->max_depth);
  44
  45                kfree(bqt->tag_index);
  46                bqt->tag_index = NULL;
  47
  48                kfree(bqt->tag_map);
  49                bqt->tag_map = NULL;
  50
  51                kfree(bqt);
  52        }
  53
  54        return retval;
  55}
  56
  57/**
  58 * __blk_queue_free_tags - release tag maintenance info
  59 * @q:  the request queue for the device
  60 *
  61 *  Notes:
  62 *    blk_cleanup_queue() will take care of calling this function, if tagging
  63 *    has been used. So there's no need to call this directly.
  64 **/
  65void __blk_queue_free_tags(struct request_queue *q)
  66{
  67        struct blk_queue_tag *bqt = q->queue_tags;
  68
  69        if (!bqt)
  70                return;
  71
  72        __blk_free_tags(bqt);
  73
  74        q->queue_tags = NULL;
  75        queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
  76}
  77
  78/**
  79 * blk_free_tags - release a given set of tag maintenance info
  80 * @bqt:        the tag map to free
  81 *
  82 * For externally managed @bqt frees the map.  Callers of this
  83 * function must guarantee to have released all the queues that
  84 * might have been using this tag map.
  85 */
  86void blk_free_tags(struct blk_queue_tag *bqt)
  87{
  88        if (unlikely(!__blk_free_tags(bqt)))
  89                BUG();
  90}
  91EXPORT_SYMBOL(blk_free_tags);
  92
  93/**
  94 * blk_queue_free_tags - release tag maintenance info
  95 * @q:  the request queue for the device
  96 *
  97 *  Notes:
  98 *      This is used to disable tagged queuing to a device, yet leave
  99 *      queue in function.
 100 **/
 101void blk_queue_free_tags(struct request_queue *q)
 102{
 103        queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
 104}
 105EXPORT_SYMBOL(blk_queue_free_tags);
 106
 107static int
 108init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
 109{
 110        struct request **tag_index;
 111        unsigned long *tag_map;
 112        int nr_ulongs;
 113
 114        if (q && depth > q->nr_requests * 2) {
 115                depth = q->nr_requests * 2;
 116                printk(KERN_ERR "%s: adjusted depth to %d\n",
 117                       __func__, depth);
 118        }
 119
 120        tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
 121        if (!tag_index)
 122                goto fail;
 123
 124        nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
 125        tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
 126        if (!tag_map)
 127                goto fail;
 128
 129        tags->real_max_depth = depth;
 130        tags->max_depth = depth;
 131        tags->tag_index = tag_index;
 132        tags->tag_map = tag_map;
 133
 134        return 0;
 135fail:
 136        kfree(tag_index);
 137        return -ENOMEM;
 138}
 139
 140static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
 141                                                   int depth)
 142{
 143        struct blk_queue_tag *tags;
 144
 145        tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
 146        if (!tags)
 147                goto fail;
 148
 149        if (init_tag_map(q, tags, depth))
 150                goto fail;
 151
 152        atomic_set(&tags->refcnt, 1);
 153        return tags;
 154fail:
 155        kfree(tags);
 156        return NULL;
 157}
 158
 159/**
 160 * blk_init_tags - initialize the tag info for an external tag map
 161 * @depth:      the maximum queue depth supported
 162 **/
 163struct blk_queue_tag *blk_init_tags(int depth)
 164{
 165        return __blk_queue_init_tags(NULL, depth);
 166}
 167EXPORT_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 * Queue lock must be held here if the function is called to resize an
 176 * existing map.
 177 **/
 178int blk_queue_init_tags(struct request_queue *q, int depth,
 179                        struct blk_queue_tag *tags)
 180{
 181        int rc;
 182
 183        BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
 184
 185        if (!tags && !q->queue_tags) {
 186                tags = __blk_queue_init_tags(q, depth);
 187
 188                if (!tags)
 189                        return -ENOMEM;
 190
 191        } else if (q->queue_tags) {
 192                rc = blk_queue_resize_tags(q, depth);
 193                if (rc)
 194                        return rc;
 195                queue_flag_set(QUEUE_FLAG_QUEUED, q);
 196                return 0;
 197        } else
 198                atomic_inc(&tags->refcnt);
 199
 200        /*
 201         * assign it, all done
 202         */
 203        q->queue_tags = tags;
 204        queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
 205        INIT_LIST_HEAD(&q->tag_busy_list);
 206        return 0;
 207}
 208EXPORT_SYMBOL(blk_queue_init_tags);
 209
 210/**
 211 * blk_queue_resize_tags - change the queueing depth
 212 * @q:  the request queue for the device
 213 * @new_depth: the new max command queueing depth
 214 *
 215 *  Notes:
 216 *    Must be called with the queue lock held.
 217 **/
 218int blk_queue_resize_tags(struct request_queue *q, int new_depth)
 219{
 220        struct blk_queue_tag *bqt = q->queue_tags;
 221        struct request **tag_index;
 222        unsigned long *tag_map;
 223        int max_depth, nr_ulongs;
 224
 225        if (!bqt)
 226                return -ENXIO;
 227
 228        /*
 229         * if we already have large enough real_max_depth.  just
 230         * adjust max_depth.  *NOTE* as requests with tag value
 231         * between new_depth and real_max_depth can be in-flight, tag
 232         * map can not be shrunk blindly here.
 233         */
 234        if (new_depth <= bqt->real_max_depth) {
 235                bqt->max_depth = new_depth;
 236                return 0;
 237        }
 238
 239        /*
 240         * Currently cannot replace a shared tag map with a new
 241         * one, so error out if this is the case
 242         */
 243        if (atomic_read(&bqt->refcnt) != 1)
 244                return -EBUSY;
 245
 246        /*
 247         * save the old state info, so we can copy it back
 248         */
 249        tag_index = bqt->tag_index;
 250        tag_map = bqt->tag_map;
 251        max_depth = bqt->real_max_depth;
 252
 253        if (init_tag_map(q, bqt, new_depth))
 254                return -ENOMEM;
 255
 256        memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 257        nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 258        memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
 259
 260        kfree(tag_index);
 261        kfree(tag_map);
 262        return 0;
 263}
 264EXPORT_SYMBOL(blk_queue_resize_tags);
 265
 266/**
 267 * blk_queue_end_tag - end tag operations for a request
 268 * @q:  the request queue for the device
 269 * @rq: the request that has completed
 270 *
 271 *  Description:
 272 *    Typically called when end_that_request_first() returns %0, meaning
 273 *    all transfers have been done for a request. It's important to call
 274 *    this function before end_that_request_last(), as that will put the
 275 *    request back on the free list thus corrupting the internal tag list.
 276 *
 277 *  Notes:
 278 *   queue lock must be held.
 279 **/
 280void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 281{
 282        struct blk_queue_tag *bqt = q->queue_tags;
 283        unsigned tag = rq->tag; /* negative tags invalid */
 284
 285        BUG_ON(tag >= bqt->real_max_depth);
 286
 287        list_del_init(&rq->queuelist);
 288        rq->cmd_flags &= ~REQ_QUEUED;
 289        rq->tag = -1;
 290
 291        if (unlikely(bqt->tag_index[tag] == NULL))
 292                printk(KERN_ERR "%s: tag %d is missing\n",
 293                       __func__, tag);
 294
 295        bqt->tag_index[tag] = NULL;
 296
 297        if (unlikely(!test_bit(tag, bqt->tag_map))) {
 298                printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 299                       __func__, tag);
 300                return;
 301        }
 302        /*
 303         * The tag_map bit acts as a lock for tag_index[bit], so we need
 304         * unlock memory barrier semantics.
 305         */
 306        clear_bit_unlock(tag, bqt->tag_map);
 307}
 308EXPORT_SYMBOL(blk_queue_end_tag);
 309
 310/**
 311 * blk_queue_start_tag - find a free tag and assign it
 312 * @q:  the request queue for the device
 313 * @rq:  the block request that needs tagging
 314 *
 315 *  Description:
 316 *    This can either be used as a stand-alone helper, or possibly be
 317 *    assigned as the queue &prep_rq_fn (in which case &struct request
 318 *    automagically gets a tag assigned). Note that this function
 319 *    assumes that any type of request can be queued! if this is not
 320 *    true for your device, you must check the request type before
 321 *    calling this function.  The request will also be removed from
 322 *    the request queue, so it's the drivers responsibility to readd
 323 *    it if it should need to be restarted for some reason.
 324 *
 325 *  Notes:
 326 *   queue lock must be held.
 327 **/
 328int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 329{
 330        struct blk_queue_tag *bqt = q->queue_tags;
 331        unsigned max_depth;
 332        int tag;
 333
 334        if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 335                printk(KERN_ERR
 336                       "%s: request %p for device [%s] already tagged %d",
 337                       __func__, rq,
 338                       rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 339                BUG();
 340        }
 341
 342        /*
 343         * Protect against shared tag maps, as we may not have exclusive
 344         * access to the tag map.
 345         *
 346         * We reserve a few tags just for sync IO, since we don't want
 347         * to starve sync IO on behalf of flooding async IO.
 348         */
 349        max_depth = bqt->max_depth;
 350        if (!rq_is_sync(rq) && max_depth > 1) {
 351                max_depth -= 2;
 352                if (!max_depth)
 353                        max_depth = 1;
 354                if (q->in_flight[BLK_RW_ASYNC] > max_depth)
 355                        return 1;
 356        }
 357
 358        do {
 359                tag = find_first_zero_bit(bqt->tag_map, max_depth);
 360                if (tag >= max_depth)
 361                        return 1;
 362
 363        } while (test_and_set_bit_lock(tag, bqt->tag_map));
 364        /*
 365         * We need lock ordering semantics given by test_and_set_bit_lock.
 366         * See blk_queue_end_tag for details.
 367         */
 368
 369        rq->cmd_flags |= REQ_QUEUED;
 370        rq->tag = tag;
 371        bqt->tag_index[tag] = rq;
 372        blk_start_request(rq);
 373        list_add(&rq->queuelist, &q->tag_busy_list);
 374        return 0;
 375}
 376EXPORT_SYMBOL(blk_queue_start_tag);
 377
 378/**
 379 * blk_queue_invalidate_tags - invalidate all pending tags
 380 * @q:  the request queue for the device
 381 *
 382 *  Description:
 383 *   Hardware conditions may dictate a need to stop all pending requests.
 384 *   In this case, we will safely clear the block side of the tag queue and
 385 *   readd all requests to the request queue in the right order.
 386 *
 387 *  Notes:
 388 *   queue lock must be held.
 389 **/
 390void blk_queue_invalidate_tags(struct request_queue *q)
 391{
 392        struct list_head *tmp, *n;
 393
 394        list_for_each_safe(tmp, n, &q->tag_busy_list)
 395                blk_requeue_request(q, list_entry_rq(tmp));
 396}
 397EXPORT_SYMBOL(blk_queue_invalidate_tags);
 398
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