2 files changed, 21 insertions, 2 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 4b95c4387e9e..bbb30d882f05 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1107,6 +1107,15 @@ static int ata_scsi_dev_config(struct scsi_device *sdev,
 
                 depth = min(sdev->host->can_queue, ata_id_queue_depth(dev->id));
                 depth = min(ATA_MAX_QUEUE - 1, depth);
+
+                /*
+                 * If this device is behind a port multiplier, we have
+                 * to share the tag map between all devices on that PMP.
+                 * Set up the shared tag map here and we get automatic.
+                 */
+                if (dev->link->ap->pmp_link)
+                        scsi_init_shared_tag_map(sdev->host, ATA_MAX_QUEUE - 1);
+
                 scsi_set_tag_type(sdev, MSG_SIMPLE_TAG);
                 scsi_activate_tcq(sdev, depth);
         }
diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index cf4c219c0b5c..17231385cb37 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;
 }
 
 /**