From: Christoph Hellwig <hch@lst.de>
Date: Sat, 6 Aug 2022 10:29:55 +0200
Subject: nvme-fc: fix the fc_appid_store return value
Patch-mainline: v6.0-rc1
Git-commit: 9317d0014499182c77a03cd095e83bcfb0f53750
References: jsc#PED-1183

"nvme-fc: fold t fc_update_appid into fc_appid_store" accidentally
changed the userspace interface for the appid attribute, because the code
that decrements "count" to remove a trailing '\n' in the parsing results
in the decremented value being incorrectly be returned from the sysfs
write.  Fix this by keeping an orig_count variable for the full length
of the write.

Fixes: c814153c83a8 ("nvme-fc: fold t fc_update_appid into fc_appid_store")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: James Smart <jsmart2021@gmail.com>
Tested-by:  Muneendra Kumar M <muneendra.kumar@broadcom.com>
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 drivers/nvme/host/fc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3882,6 +3882,7 @@ static int fc_parse_cgrpid(const char *b
 static ssize_t fc_appid_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
+	size_t orig_count = count;
 	u64 cgrp_id;
 	int appid_len = 0;
 	int cgrpid_len = 0;
@@ -3906,7 +3907,7 @@ static ssize_t fc_appid_store(struct dev
 	ret = blkcg_set_fc_appid(app_id, cgrp_id, sizeof(app_id));
 	if (ret < 0)
 		return ret;
-	return count;
+	return orig_count;
 }
 static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
 #endif /* CONFIG_BLK_CGROUP_FC_APPID */