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, 3 insertions, 8 deletions

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index e4c23939fb36..d439c0b4bfce 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -277,20 +277,14 @@ void sysfs_drop_dentry(struct sysfs_dirent *sd)
 
 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 {
-        struct dentry *dir;
         struct sysfs_dirent **pos, *sd;
         int found = 0;
 
         if (!dir_sd)
                 return -ENOENT;
 
-        dir = dir_sd->s_dentry;
+        mutex_lock(&sysfs_mutex);
 
-        if (dir->d_inode == NULL)
-                /* no inode means this hasn't been made visible yet */
-                return -ENOENT;
-
-        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
         for (pos = &dir_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
                 sd = *pos;
 
@@ -304,7 +298,8 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
                         break;
                 }
         }
-        mutex_unlock(&dir->d_inode->i_mutex);
+
+        mutex_unlock(&sysfs_mutex);
 
         if (!found)
                 return -ENOENT;