1 files changed, 396 insertions, 0 deletions

diff --git a/block/blk-tag.c b/block/blk-tag.c
new file mode 100644
index 000000000000..d1fd300e8aea
--- /dev/null
+++ b/block/blk-tag.c
@@ -0,0 +1,396 @@
+/*
+ * Functions related to tagged command queuing
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/bio.h>
+#include <linux/blkdev.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(bqt->busy);
+
+                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;
+        q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
+}
+
+/**
+ * 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 disabled tagged queuing to a device, yet leave
+ *      queue in function.
+ **/
+void blk_queue_free_tags(struct request_queue *q)
+{
+        clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
+}
+
+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",
+                                __FUNCTION__, 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;
+
+        tags->busy = 0;
+        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
+ * @tags: the tag to use
+ **/
+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
+ **/
+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)
+                        goto fail;
+        } else if (q->queue_tags) {
+                if ((rc = blk_queue_resize_tags(q, depth)))
+                        return rc;
+                set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
+                return 0;
+        } else
+                atomic_inc(&tags->refcnt);
+
+        /*
+         * assign it, all done
+         */
+        q->queue_tags = tags;
+        q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
+        INIT_LIST_HEAD(&q->tag_busy_list);
+        return 0;
+fail:
+        kfree(tags);
+        return -ENOMEM;
+}
+
+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;
+        int tag = rq->tag;
+
+        BUG_ON(tag == -1);
+
+        if (unlikely(tag >= bqt->real_max_depth))
+                /*
+                 * This can happen after tag depth has been reduced.
+                 * FIXME: how about a warning or info message here?
+                 */
+                return;
+
+        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",
+                       __FUNCTION__, 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",
+                       __FUNCTION__, 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);
+        bqt->busy--;
+}
+
+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;
+        int tag;
+
+        if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
+                printk(KERN_ERR 
+                       "%s: request %p for device [%s] already tagged %d",
+                       __FUNCTION__, 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.
+         */
+        do {
+                tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
+                if (tag >= bqt->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;
+        blkdev_dequeue_request(rq);
+        list_add(&rq->queuelist, &q->tag_busy_list);
+        bqt->busy++;
+        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);