Merge branch 'for-3.19/core' of git://git.kernel.dk/linux-block

[karo-tx-linux.git] / block / blk-mq-tag.c

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 1b7229f9354a4a1043f0e2e375af7a3c98b40ac6..e3d4e4043b496199d9f1eda8d83318cd1f9b0fe9 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -586,6 +586,34 @@ int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
        return 0;
 }
 
+/**
+ * blk_mq_unique_tag() - return a tag that is unique queue-wide
+ * @rq: request for which to compute a unique tag
+ *
+ * The tag field in struct request is unique per hardware queue but not over
+ * all hardware queues. Hence this function that returns a tag with the
+ * hardware context index in the upper bits and the per hardware queue tag in
+ * the lower bits.
+ *
+ * Note: When called for a request that is queued on a non-multiqueue request
+ * queue, the hardware context index is set to zero.
+ */
+u32 blk_mq_unique_tag(struct request *rq)
+{
+       struct request_queue *q = rq->q;
+       struct blk_mq_hw_ctx *hctx;
+       int hwq = 0;
+
+       if (q->mq_ops) {
+               hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
+               hwq = hctx->queue_num;
+       }
+
+       return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
+               (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
+}
+EXPORT_SYMBOL(blk_mq_unique_tag);
+
 ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
 {
        char *orig_page = page;