Added a new sysfs attribute appid_store under
/sys/class/fc/fc_udev_device/*

With this new interface the user can set the application identfier
in  the blkcg associted with cgroup id.

Once the application identifer has set with this interface it allows
identification of traffic sources at an individual cgroup based
Applications (ex:virtual machine (VM))level in both host and
fabric infrastructure(FC).

Below is the interface provided to set the app_id

echo "<cgroupid>:<appid>" >> /sys/class/fc/fc_udev_device/appid_store
echo "457E:100000109b521d27" >> /sys/class/fc/fc_udev_device/appid_store

Signed-off-by: Muneendra <muneendra.kumar@broadcom.com>

---
v2:
New Patch
---
 drivers/nvme/host/fc.c | 73 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index eae43bb444e0..6d6cc06fd54a 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -9,7 +9,7 @@
 #include <uapi/scsi/fc/fc_els.h>
 #include <linux/delay.h>
 #include <linux/overflow.h>
-
+#include <linux/blk-cgroup.h>
 #include "nvme.h"
 #include "fabrics.h"
 #include <linux/nvme-fc-driver.h>
@@ -3768,10 +3768,81 @@ static ssize_t nvme_fc_nvme_discovery_store(struct device *dev,
 
 	return count;
 }
+
+/*parse the Cgroup id from a buf and returns the length of cgrpid*/
+static int fc_parse_cgrpid(const char *buf, u64 *id)
+{
+	char cgrp_id[16+1];
+	int cgrpid_len, j;
+
+	memset(cgrp_id, 0x0, sizeof(cgrp_id));
+	for (cgrpid_len = 0, j = 0; cgrpid_len < 17; cgrpid_len++) {
+		if (buf[cgrpid_len] != ':')
+			cgrp_id[cgrpid_len] = buf[cgrpid_len];
+		else {
+			j = 1;
+			break;
+		}
+	}
+	if (!j)
+		return -EINVAL;
+	if (kstrtou64(cgrp_id, 16, id) < 0)
+		return -EINVAL;
+	return cgrpid_len;
+}
+
+/*
+ * fc_update_appid :parses and updates the appid in the blkcg associated with
+ * cgroupid.
+ * @buf: buf contains both cgrpid and appid info
+ * @count: size of the buffer
+ */
+static int fc_update_appid(const char *buf, size_t count)
+{
+	u64 cgrp_id;
+	int appid_len = 0;
+	int cgrpid_len = 0;
+	char app_id[APPID_LEN];
+	int ret = 0;
+
+	if (buf[count-1] == '\n')
+		count--;
+
+	if ((count > (16+1+APPID_LEN)) || (!strchr(buf, ':')))
+		return -EINVAL;
+
+	cgrpid_len = fc_parse_cgrpid(buf, &cgrp_id);
+	if (cgrpid_len < 0)
+		return -EINVAL;
+	/*appid len is count - cgrpid_len -1 (: + \n) */
+	appid_len = count - cgrpid_len - 1;
+	if (appid_len > APPID_LEN)
+		return -EINVAL;
+
+	memset(app_id, 0x0, sizeof(app_id));
+	memcpy(app_id, &buf[cgrpid_len+1], appid_len);
+	ret = blkcg_set_app_identifier(app_id, cgrp_id, sizeof(app_id));
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static ssize_t fc_appid_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	int ret  = 0;
+
+	ret = fc_update_appid(buf, count);
+	if (ret < 0)
+		return -EINVAL;
+	return count;
+}
 static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
+static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
 
 static struct attribute *nvme_fc_attrs[] = {
 	&dev_attr_nvme_discovery.attr,
+	&dev_attr_appid_store.attr,
 	NULL
 };
 
-- 
2.26.2