scsi: blkcg: Add app identifier support for blkcg

Add a unique application identifier (i.e fc_app_id member) in blkcg. This
allows identification of traffic belonging to an specific both on the host
and in the fabric infrastructure. As an example, this allows the storage
stack to uniquely identify traffic belong to particular virtual machine.

Link: https://lore.kernel.org/r/20210608043556.274139-3-muneendra.kumar@broadcom.com
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Muneendra Kumar <muneendra.kumar@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/block/Kconfig b/block/Kconfig
index a2297ed..03886d1 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -144,6 +144,15 @@
 
 	Note, this is an experimental interface and could be changed someday.
 
+config BLK_CGROUP_FC_APPID
+	bool "Enable support to track FC I/O Traffic across cgroup applications"
+	depends on BLK_CGROUP=y
+	help
+	  Enabling this option enables the support to track FC I/O traffic across
+	  cgroup applications. It enables the Fabric and the storage targets to
+	  identify, monitor, and handle FC traffic based on VM tags by inserting
+	  application specific identification into the FC frame.
+
 config BLK_CGROUP_IOCOST
 	bool "Enable support for cost model based cgroup IO controller"
 	depends on BLK_CGROUP=y