UBUNTU: Ubuntu-2.6.38-12.51

[linux-flexiantxendom0-natty.git] / block / blk-tag.c

diff --git a/block/blk-tag.c b/block/blk-tag.c
index de64e04..ece65fc 100644 (file)
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/slab.h>
 
 #include "blk.h"
 
@@ -29,7 +30,7 @@ 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
+ * 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)
@@ -38,7 +39,8 @@ static int __blk_free_tags(struct blk_queue_tag *bqt)
 
        retval = atomic_dec_and_test(&bqt->refcnt);
        if (retval) {
-               BUG_ON(bqt->busy);
+               BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
+                                                       bqt->max_depth);
 
                kfree(bqt->tag_index);
                bqt->tag_index = NULL;
@@ -70,14 +72,14 @@ void __blk_queue_free_tags(struct request_queue *q)
        __blk_free_tags(bqt);
 
        q->queue_tags = NULL;
-       queue_flag_clear(QUEUE_FLAG_QUEUED, q);
+       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
+ * 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.
  */
@@ -93,12 +95,12 @@ EXPORT_SYMBOL(blk_free_tags);
  * @q:  the request queue for the device
  *
  *  Notes:
- *     This is used to disabled tagged queuing to a device, yet leave
+ *     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(QUEUE_FLAG_QUEUED, q);
+       queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
 }
 EXPORT_SYMBOL(blk_queue_free_tags);
 
@@ -147,7 +149,6 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
        if (init_tag_map(q, tags, depth))
                goto fail;
 
-       tags->busy = 0;
        atomic_set(&tags->refcnt, 1);
        return tags;
 fail:
@@ -158,7 +159,6 @@ fail:
 /**
  * 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)
 {
@@ -171,6 +171,9 @@ EXPORT_SYMBOL(blk_init_tags);
  * @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)
@@ -197,7 +200,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth,
         * assign it, all done
         */
        q->queue_tags = tags;
-       queue_flag_set(QUEUE_FLAG_QUEUED, q);
+       queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
        INIT_LIST_HEAD(&q->tag_busy_list);
        return 0;
 fail:
@@ -268,7 +271,7 @@ EXPORT_SYMBOL(blk_queue_resize_tags);
  * @rq: the request that has completed
  *
  *  Description:
- *    Typically called when end_that_request_first() returns 0, meaning
+ *    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.
@@ -310,7 +313,6 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq)
         * unlock memory barrier semantics.
         */
        clear_bit_unlock(tag, bqt->tag_map);
-       bqt->busy--;
 }
 EXPORT_SYMBOL(blk_queue_end_tag);
 
@@ -335,6 +337,7 @@ EXPORT_SYMBOL(blk_queue_end_tag);
 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))) {
@@ -348,10 +351,22 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
        /*
         * 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, bqt->max_depth);
-               if (tag >= bqt->max_depth)
+               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));
@@ -363,9 +378,8 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
        rq->cmd_flags |= REQ_QUEUED;
        rq->tag = tag;
        bqt->tag_index[tag] = rq;
-       blkdev_dequeue_request(rq);
+       blk_start_request(rq);
        list_add(&rq->queuelist, &q->tag_busy_list);
-       bqt->busy++;
        return 0;
 }
 EXPORT_SYMBOL(blk_queue_start_tag);