[PATCH] helper function for retrieving scsi_cmd given host based block layer tag

This was necessitated by the need for a function to get back
to a scsi_cmnd, when an hba the posts its (corresponding) completion
interrupt with a block layer tag as its reference.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: David Somayajulu <david.somayajulu@qlogic.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1d79b8d4ca6d..26f7856ff812 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -769,6 +769,14 @@ extern struct blk_queue_tag *blk_init_tags(int);
 extern void blk_free_tags(struct blk_queue_tag *);
 extern void blk_congestion_end(int rw);
 
+static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
+                                                int tag)
+{
+        if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
+                return NULL;
+        return bqt->tag_index[tag];
+}
+
 extern void blk_rq_bio_prep(request_queue_t *, struct request *, struct bio *);
 extern int blkdev_issue_flush(struct block_device *, sector_t *);