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>

1 files changed, 12 insertions, 2 deletions

diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index cf4c219c0b5..17231385cb3 100644
--- 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;
 }
 
 /**