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

[safe/jmp/linux-2.6] / include / scsi / scsi_tcq.h

diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index bbf6621..1723138 100644 (file)
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -6,7 +6,6 @@
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_host.h>
 
-
 #define MSG_SIMPLE_TAG 0x20
 #define MSG_HEAD_TAG   0x21
 #define MSG_ORDERED_TAG        0x22
@@ -14,6 +13,7 @@
 #define SCSI_NO_TAG    (-1)    /* identify no tag in use */
 
 
+#ifdef CONFIG_BLOCK
 
 /**
  * scsi_get_tag_type - get the type of tag the device supports
@@ -140,8 +140,39 @@ 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;
+}
+
+/**
+ * scsi_host_find_tag - find the tagged command by host
+ * @shost:     pointer to scsi_host
+ * @tag:       tag of the scsi_cmnd
+ *
+ * Notes:
+ *     Only works with tags allocated by the generic blk layer.
+ **/
+static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
+                                               int tag)
+{
+       struct request *req;
+
+       if (tag != SCSI_NO_TAG) {
+               req = blk_map_queue_find_tag(shost->bqt, tag);
+               return req ? (struct scsi_cmnd *)req->special : NULL;
+       }
+       return NULL;
 }
 
+#endif /* CONFIG_BLOCK */
 #endif /* _SCSI_SCSI_TCQ_H */