scsi: make sure that scsi_init_shared_tag_map() doesn't overwrite existing map

Right now callers have to check whether scsi_host->bqt is already
set up, it's much cleaner to just have scsi_init_shared_tag_map()
does this check on its own.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index cf4c219..1723138 100644 (file)
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -140,8 +140,18 @@ static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
  */
 static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
 {
-       shost->bqt = blk_init_tags(depth);
-       return shost->bqt ? 0 : -ENOMEM;
+       /*
+        * If the shared tag map isn't already initialized, do it now.
+        * This saves callers from having to check ->bqt when setting up
+        * devices on the shared host (for libata)
+        */
+       if (!shost->bqt) {
+               shost->bqt = blk_init_tags(depth);
+               if (!shost->bqt)
+                       return -ENOMEM;
+       }
+
+       return 0;
 }
 
 /**