FreeBSD/Linux Kernel Cross Reference
sys/block/blk-tag.c

     /*
      * Functions related to tagged command queuing
      */
     #include <linux/kernel.h>
     #include <linux/module.h>
     #include <linux/bio.h>
     #include <linux/blkdev.h>
     #include <linux/slab.h>
     
    #include "blk.h"
    
    /**
     * blk_queue_find_tag - find a request by its tag and queue
     * @q:   The request queue for the device
     * @tag: The tag of the request
     *
     * Notes:
     *    Should be used when a device returns a tag and you want to match
     *    it with a request.
     *
     *    no locks need be held.
     **/
    struct request *blk_queue_find_tag(struct request_queue *q, int tag)
    {
            return blk_map_queue_find_tag(q->queue_tags, tag);
    }
    EXPORT_SYMBOL(blk_queue_find_tag);
    
    /**
     * __blk_free_tags - release a given set of tag maintenance info
     * @bqt:        the tag map to free
     *
     * Tries to free the specified @bqt.  Returns true if it was
     * actually freed and false if there are still references using it
     */
    static int __blk_free_tags(struct blk_queue_tag *bqt)
    {
            int retval;
    
            retval = atomic_dec_and_test(&bqt->refcnt);
            if (retval) {
                    BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
                                                            bqt->max_depth);
    
                    kfree(bqt->tag_index);
                    bqt->tag_index = NULL;
    
                    kfree(bqt->tag_map);
                    bqt->tag_map = NULL;
    
                    kfree(bqt);
            }
    
            return retval;
    }
    
    /**
     * __blk_queue_free_tags - release tag maintenance info
     * @q:  the request queue for the device
     *
     *  Notes:
     *    blk_cleanup_queue() will take care of calling this function, if tagging
     *    has been used. So there's no need to call this directly.
     **/
    void __blk_queue_free_tags(struct request_queue *q)
    {
            struct blk_queue_tag *bqt = q->queue_tags;
    
            if (!bqt)
                    return;
    
            __blk_free_tags(bqt);
    
            q->queue_tags = NULL;
            queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
    }
    
    /**
     * blk_free_tags - release a given set of tag maintenance info
     * @bqt:        the tag map to free
     *
     * For externally managed @bqt frees the map.  Callers of this
     * function must guarantee to have released all the queues that
     * might have been using this tag map.
     */
    void blk_free_tags(struct blk_queue_tag *bqt)
    {
            if (unlikely(!__blk_free_tags(bqt)))
                    BUG();
    }
    EXPORT_SYMBOL(blk_free_tags);
    
    /**
     * blk_queue_free_tags - release tag maintenance info
     * @q:  the request queue for the device
     *
     *  Notes:
     *      This is used to disable tagged queuing to a device, yet leave
     *      queue in function.
    **/
   void blk_queue_free_tags(struct request_queue *q)
   {
           queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
   }
   EXPORT_SYMBOL(blk_queue_free_tags);
   
   static int
   init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
   {
           struct request **tag_index;
           unsigned long *tag_map;
           int nr_ulongs;
   
           if (q && depth > q->nr_requests * 2) {
                   depth = q->nr_requests * 2;
                   printk(KERN_ERR "%s: adjusted depth to %d\n",
                          __func__, depth);
           }
   
           tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
           if (!tag_index)
                   goto fail;
   
           nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
           tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
           if (!tag_map)
                   goto fail;
   
           tags->real_max_depth = depth;
           tags->max_depth = depth;
           tags->tag_index = tag_index;
           tags->tag_map = tag_map;
   
           return 0;
   fail:
           kfree(tag_index);
           return -ENOMEM;
   }
   
   static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
                                                      int depth)
   {
           struct blk_queue_tag *tags;
   
           tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
           if (!tags)
                   goto fail;
   
           if (init_tag_map(q, tags, depth))
                   goto fail;
   
           atomic_set(&tags->refcnt, 1);
           return tags;
   fail:
           kfree(tags);
           return NULL;
   }
   
   /**
    * blk_init_tags - initialize the tag info for an external tag map
    * @depth:      the maximum queue depth supported
    **/
   struct blk_queue_tag *blk_init_tags(int depth)
   {
           return __blk_queue_init_tags(NULL, depth);
   }
   EXPORT_SYMBOL(blk_init_tags);
   
   /**
    * blk_queue_init_tags - initialize the queue tag info
    * @q:  the request queue for the device
    * @depth:  the maximum queue depth supported
    * @tags: the tag to use
    *
    * Queue lock must be held here if the function is called to resize an
    * existing map.
    **/
   int blk_queue_init_tags(struct request_queue *q, int depth,
                           struct blk_queue_tag *tags)
   {
           int rc;
   
           BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
   
           if (!tags && !q->queue_tags) {
                   tags = __blk_queue_init_tags(q, depth);
   
                   if (!tags)
                           return -ENOMEM;
   
           } else if (q->queue_tags) {
                   rc = blk_queue_resize_tags(q, depth);
                   if (rc)
                           return rc;
                   queue_flag_set(QUEUE_FLAG_QUEUED, q);
                   return 0;
           } else
                   atomic_inc(&tags->refcnt);
   
           /*
            * assign it, all done
            */
           q->queue_tags = tags;
           queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
           INIT_LIST_HEAD(&q->tag_busy_list);
           return 0;
   }
   EXPORT_SYMBOL(blk_queue_init_tags);
   
   /**
    * blk_queue_resize_tags - change the queueing depth
    * @q:  the request queue for the device
    * @new_depth: the new max command queueing depth
    *
    *  Notes:
    *    Must be called with the queue lock held.
    **/
   int blk_queue_resize_tags(struct request_queue *q, int new_depth)
   {
           struct blk_queue_tag *bqt = q->queue_tags;
           struct request **tag_index;
           unsigned long *tag_map;
           int max_depth, nr_ulongs;
   
           if (!bqt)
                   return -ENXIO;
   
           /*
            * if we already have large enough real_max_depth.  just
            * adjust max_depth.  *NOTE* as requests with tag value
            * between new_depth and real_max_depth can be in-flight, tag
            * map can not be shrunk blindly here.
            */
           if (new_depth <= bqt->real_max_depth) {
                   bqt->max_depth = new_depth;
                   return 0;
           }
   
           /*
            * Currently cannot replace a shared tag map with a new
            * one, so error out if this is the case
            */
           if (atomic_read(&bqt->refcnt) != 1)
                   return -EBUSY;
   
           /*
            * save the old state info, so we can copy it back
            */
           tag_index = bqt->tag_index;
           tag_map = bqt->tag_map;
           max_depth = bqt->real_max_depth;
   
           if (init_tag_map(q, bqt, new_depth))
                   return -ENOMEM;
   
           memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
           nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
           memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
   
           kfree(tag_index);
           kfree(tag_map);
           return 0;
   }
   EXPORT_SYMBOL(blk_queue_resize_tags);
   
   /**
    * blk_queue_end_tag - end tag operations for a request
    * @q:  the request queue for the device
    * @rq: the request that has completed
    *
    *  Description:
    *    Typically called when end_that_request_first() returns %0, meaning
    *    all transfers have been done for a request. It's important to call
    *    this function before end_that_request_last(), as that will put the
    *    request back on the free list thus corrupting the internal tag list.
    *
    *  Notes:
    *   queue lock must be held.
    **/
   void blk_queue_end_tag(struct request_queue *q, struct request *rq)
   {
           struct blk_queue_tag *bqt = q->queue_tags;
           unsigned tag = rq->tag; /* negative tags invalid */
   
           BUG_ON(tag >= bqt->real_max_depth);
   
           list_del_init(&rq->queuelist);
           rq->cmd_flags &= ~REQ_QUEUED;
           rq->tag = -1;
   
           if (unlikely(bqt->tag_index[tag] == NULL))
                   printk(KERN_ERR "%s: tag %d is missing\n",
                          __func__, tag);
   
           bqt->tag_index[tag] = NULL;
   
           if (unlikely(!test_bit(tag, bqt->tag_map))) {
                   printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
                          __func__, tag);
                   return;
           }
           /*
            * The tag_map bit acts as a lock for tag_index[bit], so we need
            * unlock memory barrier semantics.
            */
           clear_bit_unlock(tag, bqt->tag_map);
   }
   EXPORT_SYMBOL(blk_queue_end_tag);
   
   /**
    * blk_queue_start_tag - find a free tag and assign it
    * @q:  the request queue for the device
    * @rq:  the block request that needs tagging
    *
    *  Description:
    *    This can either be used as a stand-alone helper, or possibly be
    *    assigned as the queue &prep_rq_fn (in which case &struct request
    *    automagically gets a tag assigned). Note that this function
    *    assumes that any type of request can be queued! if this is not
    *    true for your device, you must check the request type before
    *    calling this function.  The request will also be removed from
    *    the request queue, so it's the drivers responsibility to readd
    *    it if it should need to be restarted for some reason.
    *
    *  Notes:
    *   queue lock must be held.
    **/
   int blk_queue_start_tag(struct request_queue *q, struct request *rq)
   {
           struct blk_queue_tag *bqt = q->queue_tags;
           unsigned max_depth;
           int tag;
   
           if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
                   printk(KERN_ERR
                          "%s: request %p for device [%s] already tagged %d",
                          __func__, rq,
                          rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
                   BUG();
           }
   
           /*
            * Protect against shared tag maps, as we may not have exclusive
            * access to the tag map.
            *
            * We reserve a few tags just for sync IO, since we don't want
            * to starve sync IO on behalf of flooding async IO.
            */
           max_depth = bqt->max_depth;
           if (!rq_is_sync(rq) && max_depth > 1) {
                   max_depth -= 2;
                   if (!max_depth)
                           max_depth = 1;
                   if (q->in_flight[BLK_RW_ASYNC] > max_depth)
                           return 1;
           }
   
           do {
                   tag = find_first_zero_bit(bqt->tag_map, max_depth);
                   if (tag >= max_depth)
                           return 1;
   
           } while (test_and_set_bit_lock(tag, bqt->tag_map));
           /*
            * We need lock ordering semantics given by test_and_set_bit_lock.
            * See blk_queue_end_tag for details.
            */
   
           rq->cmd_flags |= REQ_QUEUED;
           rq->tag = tag;
           bqt->tag_index[tag] = rq;
           blk_start_request(rq);
           list_add(&rq->queuelist, &q->tag_busy_list);
           return 0;
   }
   EXPORT_SYMBOL(blk_queue_start_tag);
   
   /**
    * blk_queue_invalidate_tags - invalidate all pending tags
    * @q:  the request queue for the device
    *
    *  Description:
    *   Hardware conditions may dictate a need to stop all pending requests.
    *   In this case, we will safely clear the block side of the tag queue and
    *   readd all requests to the request queue in the right order.
    *
    *  Notes:
    *   queue lock must be held.
    **/
   void blk_queue_invalidate_tags(struct request_queue *q)
   {
           struct list_head *tmp, *n;
   
           list_for_each_safe(tmp, n, &q->tag_busy_list)
                   blk_requeue_request(q, list_entry_rq(tmp));
   }
   EXPORT_SYMBOL(blk_queue_invalidate_tags);

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