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-rw-r--r--block/blk-mq-tag.c28
-rw-r--r--block/blk-mq.c2
2 files changed, 30 insertions, 0 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 8317175a3009..728b9a4d5f56 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -584,6 +584,34 @@ 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;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 68929bad9a6a..b5896d436fc9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2024,6 +2024,8 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
*/
int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
{
+ BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
+
if (!set->nr_hw_queues)
return -EINVAL;
if (!set->queue_depth)