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, 15 insertions, 16 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 20703b9ee064..d0deed3e60b5 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -415,29 +415,28 @@ const struct file_operations sysfs_file_operations = {
 int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
                    int type)
 {
-        struct dentry *dir = dir_sd->s_dentry;
         umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
         struct sysfs_dirent *sd;
-        int error = 0;
 
-        mutex_lock(&dir->d_inode->i_mutex);
+        sd = sysfs_new_dirent(attr->name, mode, type);
+        if (!sd)
+                return -ENOMEM;
+        sd->s_elem.attr.attr = (void *)attr;
 
-        if (sysfs_find_dirent(dir_sd, attr->name)) {
-                error = -EEXIST;
-                goto out_unlock;
-        }
+        mutex_lock(&sysfs_mutex);
 
-        sd = sysfs_new_dirent(attr->name, mode, type);
-        if (!sd) {
-                error = -ENOMEM;
-                goto out_unlock;
+        if (!sysfs_find_dirent(dir_sd, attr->name)) {
+                sysfs_attach_dirent(sd, dir_sd, NULL);
+                sd = NULL;
         }
-        sd->s_elem.attr.attr = (void *)attr;
-        sysfs_attach_dirent(sd, dir_sd, NULL);
 
- out_unlock:
-        mutex_unlock(&dir->d_inode->i_mutex);
-        return error;
+        mutex_unlock(&sysfs_mutex);
+
+        if (sd) {
+                sysfs_put(sd);
+                return -EEXIST;
+        }
+        return 0;
 }