[PATCH 24/26] sysfs: Make sysfs_rename_link atomic

[Eric W. Biederman]

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

Use the existing sysfs_rename to make sysfs_rename_link an atomic
operation that does less work.  While I am at add additional sanity
checking to ensure it is a symlink I am renaming.

Acked-by: Kay Sievers <kay.sievers@xxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
---
 fs/sysfs/symlink.c |   26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index fc5fc86..39d050b 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -106,8 +106,30 @@ void sysfs_remove_link(struct kobject * kobj, const char * name)
 int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
 			const char *old, const char *new)
 {
-	sysfs_remove_link(kobj, old);
-	return sysfs_create_link(kobj, targ, new);
+	struct sysfs_dirent *parent_sd, *sd = NULL;
+	int result;
+
+	if (!kobj)
+		parent_sd = &sysfs_root;
+	else
+		parent_sd = kobj->sd;
+
+	result = -ENOENT;
+	sd = sysfs_get_dirent(parent_sd, old);
+	if (!sd)
+		goto out;
+
+	result = -EINVAL;
+	if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
+		goto out;
+	if (sd->s_symlink.target_sd->s_dir.kobj != targ)
+		goto out;
+
+	result = sysfs_rename(sd, parent_sd, new);
+
+out:
+	sysfs_put(sd);
+	return result;
 }
 
 static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
-- 
1.6.3.1.54.g99dd.dirty

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