linux-kernel - [PATCH v6 2/6] sysfs: wrap __compat_only_sysfs_link_entry_to

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Date:   Wed, 11 Dec 2019 21:39:06 +0530
From:   Sourabh Jain <sourabhjain@...ux.ibm.com>
To:     mpe@...erman.id.au
Cc:     mahesh@...ux.vnet.ibm.com, hbathini@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
        corbet@....net, linux-doc@...r.kernel.org,
        gregkh@...uxfoundation.org,
        Sourabh Jain <sourabhjain@...ux.ibm.com>
Subject: [PATCH v6 2/6] sysfs: wrap __compat_only_sysfs_link_entry_to_kobj function to change the symlink name

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 compat_only_sysfs_link_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@...ux.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..0993645f0b59 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 compat_only_sysfs_link_entry_to_kobj(kobj, target_kobj,
+						target_name, NULL);
+}
+EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
+
+/**
+ * compat_only_sysfs_link_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 compat_only_sysfs_link_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(compat_only_sysfs_link_entry_to_kobj);
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 5420817ed317..15b195a4529d 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 compat_only_sysfs_link_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 compat_only_sysfs_link_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