[SCSI] add shared tag map helpers
This patch adds support for sharing tag maps at the host level
(i.e. either every queue [LUN] has its own tag map or there's a single
one for the entire host). This formulation is primarily intended to
help single issue queue hardware, like the aic7xxx
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index f244d4f..68ef163 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -265,6 +265,9 @@
destroy_workqueue(shost->work_q);
scsi_destroy_command_freelist(shost);
+ if (shost->bqt)
+ blk_free_tags(shost->bqt);
+
kfree(shost->shost_data);
if (parent)
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index b3dd90f..39c6f8c 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -16,6 +16,7 @@
struct Scsi_Host;
struct scsi_host_cmd_pool;
struct scsi_transport_template;
+struct blk_queue_tags;
/*
@@ -466,6 +467,12 @@
struct scsi_transport_template *transportt;
/*
+ * area to keep a shared tag map (if needed, will be
+ * NULL if not)
+ */
+ struct blk_queue_tag *bqt;
+
+ /*
* The following two fields are protected with host_lock;
* however, eh routines can safely access during eh processing
* without acquiring the lock.
diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
index e47e36a..4eea254 100644
--- a/include/scsi/scsi_tcq.h
+++ b/include/scsi/scsi_tcq.h
@@ -4,6 +4,7 @@
#include <linux/blkdev.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
#define MSG_SIMPLE_TAG 0x20
@@ -66,7 +67,8 @@
return;
if (!blk_queue_tagged(sdev->request_queue))
- blk_queue_init_tags(sdev->request_queue, depth, NULL);
+ blk_queue_init_tags(sdev->request_queue, depth,
+ sdev->host->bqt);
scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
}
@@ -131,4 +133,14 @@
return sdev->current_cmnd;
}
+/**
+ * scsi_init_shared_tag_map - create a shared tag map
+ * @shost: the host to share the tag map among all devices
+ * @depth: the total depth of the map
+ */
+static inline void scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
+{
+ shost->bqt = blk_init_tags(depth);
+}
+
#endif /* _SCSI_SCSI_TCQ_H */