[PATCH] blk layer tag resize

This allows drivers to resize their tag depth at run-time.

drivers/block/ll_rw_blk.c

@@ -413,11 +413,12 @@ struct request *blk_queue_find_tag(request_queue_t *q, int tag)
 {
 	struct blk_queue_tag *bqt = q->queue_tags;
 
-	if (unlikely(bqt == NULL || bqt->max_depth < tag))
+	if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
 		return NULL;
 
 	return bqt->tag_index[tag];
 }
+
 /**
  * blk_queue_free_tags - release tag maintenance info
  * @q:  the request queue for the device
@@ -448,39 +449,28 @@ void blk_queue_free_tags(request_queue_t *q)
 	q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
 }
 
-/**
- * blk_queue_init_tags - initialize the queue tag info
- * @q:  the request queue for the device
- * @depth:  the maximum queue depth supported
- **/
-int blk_queue_init_tags(request_queue_t *q, int depth)
+static int init_tag_map(struct blk_queue_tag *tags, int depth)
 {
-	struct blk_queue_tag *tags;
 	int bits, i;
 
 	if (depth > (queue_nr_requests*2)) {
 		depth = (queue_nr_requests*2);
-		printk("blk_queue_init_tags: adjusted depth to %d\n", depth);
+		printk(KERN_ERR "%s: adjusted depth to %d\n", __FUNCTION__, depth);
 	}
 
-	tags = kmalloc(sizeof(struct blk_queue_tag),GFP_ATOMIC);
-	if (!tags)
-		goto fail;
-
 	tags->tag_index = kmalloc(depth * sizeof(struct request *), GFP_ATOMIC);
 	if (!tags->tag_index)
-		goto fail_index;
+		goto fail;
 
 	bits = (depth / BLK_TAGS_PER_LONG) + 1;
 	tags->tag_map = kmalloc(bits * sizeof(unsigned long), GFP_ATOMIC);
 	if (!tags->tag_map)
-		goto fail_map;
+		goto fail;
 
 	memset(tags->tag_index, 0, depth * sizeof(struct request *));
 	memset(tags->tag_map, 0, bits * sizeof(unsigned long));
-	INIT_LIST_HEAD(&tags->busy_list);
-	tags->busy = 0;
 	tags->max_depth = depth;
+	tags->real_max_depth = bits * BITS_PER_LONG;
 
 	/*
 	 * set the upper bits if the depth isn't a multiple of the word size
@@ -488,21 +478,88 @@ int blk_queue_init_tags(request_queue_t *q, int depth)
 	for (i = depth; i < bits * BLK_TAGS_PER_LONG; i++)
 		__set_bit(i, tags->tag_map);
 
+	return 0;
+fail:
+	kfree(tags->tag_index);
+	return -ENOMEM;
+}
+
+
+/**
+ * blk_queue_init_tags - initialize the queue tag info
+ * @q:  the request queue for the device
+ * @depth:  the maximum queue depth supported
+ **/
+int blk_queue_init_tags(request_queue_t *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(tags, depth))
+		goto fail;
+
+	INIT_LIST_HEAD(&tags->busy_list);
+	tags->busy = 0;
+
 	/*
 	 * assign it, all done
 	 */
 	q->queue_tags = tags;
 	q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
 	return 0;
-
-fail_map:
-	kfree(tags->tag_index);
-fail_index:
-	kfree(tags);
 fail:
+	kfree(tags);
 	return -ENOMEM;
 }
 
+/**
+ * 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(request_queue_t *q, int new_depth)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+	struct request **tag_index;
+	unsigned long *tag_map;
+	int bits, max_depth;
+
+	if (!bqt)
+		return -ENXIO;
+
+	/*
+	 * don't bother sizing down
+	 */
+	if (new_depth <= bqt->real_max_depth) {
+		bqt->max_depth = new_depth;
+		return 0;
+	}
+
+	/*
+	 * 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(bqt, new_depth))
+		return -ENOMEM;
+
+	memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
+	bits = max_depth / BLK_TAGS_PER_LONG;
+	memcpy(bqt->tag_map, bqt->tag_map, bits * sizeof(unsigned long));
+
+	kfree(tag_index);
+	kfree(tag_map);
+	return 0;
+}
+
 /**
  * blk_queue_end_tag - end tag operations for a request
  * @q:  the request queue for the device
@@ -524,7 +581,7 @@ void blk_queue_end_tag(request_queue_t *q, struct request *rq)
 
 	BUG_ON(tag == -1);
 
-	if (unlikely(tag >= bqt->max_depth))
+	if (unlikely(tag >= bqt->real_max_depth))
 		return;
 
 	if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {

include/linux/blkdev.h

@@ -179,7 +179,8 @@ struct blk_queue_tag {
 	unsigned long *tag_map;		/* bit map of free/busy tags */
 	struct list_head busy_list;	/* fifo list of busy tags */
 	int busy;			/* current depth */
-	int max_depth;
+	int max_depth;			/* what we will send to device */
+	int real_max_depth;		/* what the array can hold */
 };
 
 struct request_queue
@@ -452,6 +453,7 @@ extern struct request *blk_queue_find_tag(request_queue_t *, int);
 extern void blk_queue_end_tag(request_queue_t *, struct request *);
 extern int blk_queue_init_tags(request_queue_t *, int);
 extern void blk_queue_free_tags(request_queue_t *);
+extern int blk_queue_resize_tags(request_queue_t *, int);
 extern void blk_queue_invalidate_tags(request_queue_t *);
 extern void blk_congestion_wait(int rw, long timeout);