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From:   Sourabh Jain <sourabhjain@linux.ibm.com>
To:     mpe@ellerman.id.au
Cc:     mahesh@linux.vnet.ibm.com, hbathini@linux.ibm.com,
        linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
        corbet@lwn.net, linux-doc@vger.kernel.org,
        gregkh@linuxfoundation.org,
        Sourabh Jain <sourabhjain@linux.ibm.com>
Subject: [PATCH v4 2/6] sysfs: wrap __compat_only_sysfs_link_entry_to_kobj function to change the symlink name
Date:   Fri,  6 Dec 2019 17:54:30 +0530
In-Reply-To: <20191206122434.29587-1-sourabhjain@linux.ibm.com>
References: <20191206122434.29587-1-sourabhjain@linux.ibm.com>
Message-Id: <20191206122434.29587-3-sourabhjain@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The __compat_only_sysfs_link_entry_to_kobj function creates a symlink to a
kobject but doesn't provide an option to change the symlink file name.

This patch adds a wrapper function create_sysfs_symlink_entry_to_kobj that
extends the __compat_only_sysfs_link_entry_to_kobj functionality which
allows function caller to customize the symlink name.

Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 fs/sysfs/group.c      | 28 +++++++++++++++++++++++++---
 include/linux/sysfs.h | 12 ++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index d41c21fef138..5eb38145b957 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -424,6 +424,25 @@ EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
 int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
 				      struct kobject *target_kobj,
 				      const char *target_name)
+{
+	return create_sysfs_symlink_entry_to_kobj(kobj, target_kobj,
+						target_name, NULL);
+}
+EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
+
+/**
+ * create_sysfs_symlink_entry_to_kobj - add a symlink to a kobject pointing
+ * to a group or an attribute
+ * @kobj:		The kobject containing the group.
+ * @target_kobj:	The target kobject.
+ * @target_name:	The name of the target group or attribute.
+ * @symlink_name:	The name of the symlink file (target_name will be
+ *			considered if symlink_name is NULL).
+ */
+int create_sysfs_symlink_entry_to_kobj(struct kobject *kobj,
+				       struct kobject *target_kobj,
+				       const char *target_name,
+				       const char *symlink_name)
 {
 	struct kernfs_node *target;
 	struct kernfs_node *entry;
@@ -448,12 +467,15 @@ int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
 		return -ENOENT;
 	}
 
-	link = kernfs_create_link(kobj->sd, target_name, entry);
+	if (!symlink_name)
+		symlink_name = target_name;
+
+	link = kernfs_create_link(kobj->sd, symlink_name, entry);
 	if (IS_ERR(link) && PTR_ERR(link) == -EEXIST)
-		sysfs_warn_dup(kobj->sd, target_name);
+		sysfs_warn_dup(kobj->sd, symlink_name);
 
 	kernfs_put(entry);
 	kernfs_put(target);
 	return PTR_ERR_OR_ZERO(link);
 }
-EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
+EXPORT_SYMBOL_GPL(create_sysfs_symlink_entry_to_kobj);
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 5420817ed317..123c6f10333a 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -300,6 +300,10 @@ void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
 int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
 				      struct kobject *target_kobj,
 				      const char *target_name);
+int create_sysfs_symlink_entry_to_kobj(struct kobject *kobj,
+				       struct kobject *target_kobj,
+				       const char *target_name,
+				       const char *symlink_name);
 
 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr);
 
@@ -508,6 +512,14 @@ static inline int __compat_only_sysfs_link_entry_to_kobj(
 	return 0;
 }
 
+static int create_sysfs_symlink_entry_to_kobj(struct kobject *kobj,
+					      struct kobject *target_kobj,
+					      const char *target_name,
+					      const char *symlink_name)
+{
+	return 0;
+}
+
 static inline void sysfs_notify(struct kobject *kobj, const char *dir,
 				const char *attr)
 {
-- 
2.17.2