sysfs: use sysfs_mutex to protect the sysfs_dirent tree

As kobj sysfs dentries and inodes are gonna be made reclaimable,
i_mutex can't be used to protect sysfs_dirent tree.  Use sysfs_mutex
globally instead.  As the whole tree is protected with sysfs_mutex,
there is no reason to keep sysfs_rename_sem.  Drop it.

While at it, add docbook comments to functions which require
sysfs_mutex locking.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 26 insertions, 25 deletions

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index cbd95a4109de..683316f0aa96 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -44,20 +44,6 @@ static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
         }
 }
 
-static int sysfs_add_link(struct sysfs_dirent * parent_sd, const char * name,
-                          struct sysfs_dirent * target_sd)
-{
-        struct sysfs_dirent * sd;
-
-        sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
-        if (!sd)
-                return -ENOMEM;
-
-        sd->s_elem.symlink.target_sd = target_sd;
-        sysfs_attach_dirent(sd, parent_sd, NULL);
-        return 0;
-}
-
 /**
  *      sysfs_create_link - create symlink between two objects.
  *      @kobj:  object whose directory we're creating the link in.
@@ -68,7 +54,8 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
 {
         struct sysfs_dirent *parent_sd = NULL;
         struct sysfs_dirent *target_sd = NULL;
-        int error = -EEXIST;
+        struct sysfs_dirent *sd = NULL;
+        int error;
 
         BUG_ON(!name);
 
@@ -78,8 +65,9 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
         } else
                 parent_sd = kobj->sd;
 
+        error = -EFAULT;
         if (!parent_sd)
-                return -EFAULT;
+                goto out_put;
 
         /* target->sd can go away beneath us but is protected with
          * sysfs_assoc_lock.  Fetch target_sd from it.
@@ -89,17 +77,30 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
                 target_sd = sysfs_get(target->sd);
         spin_unlock(&sysfs_assoc_lock);
 
+        error = -ENOENT;
         if (!target_sd)
-                return -ENOENT;
+                goto out_put;
+
+        error = -ENOMEM;
+        sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
+        if (!sd)
+                goto out_put;
+        sd->s_elem.symlink.target_sd = target_sd;
 
-        mutex_lock(&parent_sd->s_dentry->d_inode->i_mutex);
-        if (!sysfs_find_dirent(parent_sd, name))
-                error = sysfs_add_link(parent_sd, name, target_sd);
-        mutex_unlock(&parent_sd->s_dentry->d_inode->i_mutex);
+        mutex_lock(&sysfs_mutex);
+        error = -EEXIST;
+        if (sysfs_find_dirent(parent_sd, name))
+                goto out_unlock;
+        sysfs_attach_dirent(sd, parent_sd, NULL);
+        mutex_unlock(&sysfs_mutex);
 
-        if (error)
-                sysfs_put(target_sd);
+        return 0;
 
+ out_unlock:
+        mutex_unlock(&sysfs_mutex);
+ out_put:
+        sysfs_put(target_sd);
+        sysfs_put(sd);
         return error;
 }
 
@@ -144,9 +145,9 @@ static int sysfs_getlink(struct dentry *dentry, char * path)
         struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd;
         int error;
 
-        down_read(&sysfs_rename_sem);
+        mutex_lock(&sysfs_mutex);
         error = sysfs_get_target_path(parent_sd, target_sd, path);
-        up_read(&sysfs_rename_sem);
+        mutex_unlock(&sysfs_mutex);
 
         return error;
 }