sysfs: simply sysfs_get_dentry

Now that we know the sysfs tree structure cannot change under us and
sysfs shadow support is dropped, sysfs_get_dentry() can be simplified
greatly.  It can just look up from the root and there's no need to
retry on failure.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 75 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 9fe83d23dc2c..1c3dc5d01ccd 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -78,9 +78,8 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
  *      @sd: sysfs_dirent of interest
  *
  *      Get dentry for @sd.  Dentry is looked up if currently not
- *      present.  This function climbs sysfs_dirent tree till it
- *      reaches a sysfs_dirent with valid dentry attached and descends
- *      down from there looking up dentry for each step.
+ *      present.  This function descends from the root looking up
+ *      dentry for each step.
  *
  *      LOCKING:
  *      mutex_lock(sysfs_rename_mutex)
@@ -90,86 +89,28 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
  */
 struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
 {
-        struct sysfs_dirent *cur;
-        struct dentry *parent_dentry, *dentry;
-        int i, depth;
+        struct dentry *dentry = dget(sysfs_sb->s_root);
 
-        /* Find the first parent which has valid s_dentry and get the
-         * dentry.
-         */
-        mutex_lock(&sysfs_mutex);
- restart0:
-        spin_lock(&sysfs_assoc_lock);
- restart1:
-        spin_lock(&dcache_lock);
-
-        dentry = NULL;
-        depth = 0;
-        cur = sd;
-        while (!cur->s_dentry || !cur->s_dentry->d_inode) {
-                if (cur->s_flags & SYSFS_FLAG_REMOVED) {
-                        dentry = ERR_PTR(-ENOENT);
-                        depth = 0;
-                        break;
-                }
-                cur = cur->s_parent;
-                depth++;
-        }
-        if (!IS_ERR(dentry))
-                dentry = dget_locked(cur->s_dentry);
+        while (dentry->d_fsdata != sd) {
+                struct sysfs_dirent *cur;
+                struct dentry *parent;
 
-        spin_unlock(&dcache_lock);
-        spin_unlock(&sysfs_assoc_lock);
-
-        /* from the found dentry, look up depth times */
-        while (depth--) {
-                /* find and get depth'th ancestor */
-                for (cur = sd, i = 0; cur && i < depth; i++)
+                /* find the first ancestor which hasn't been looked up */
+                cur = sd;
+                while (cur->s_parent != dentry->d_fsdata)
                         cur = cur->s_parent;
 
-                /* This can happen if tree structure was modified due
-                 * to move/rename.  Restart.
-                 */
-                if (i != depth) {
-                        dput(dentry);
-                        goto restart0;
-                }
-
-                sysfs_get(cur);
-
-                mutex_unlock(&sysfs_mutex);
-
                 /* look it up */
-                parent_dentry = dentry;
-                mutex_lock(&parent_dentry->d_inode->i_mutex);
-                dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
+                parent = dentry;
+                mutex_lock(&parent->d_inode->i_mutex);
+                dentry = lookup_one_len_kern(cur->s_name, parent,
                                              strlen(cur->s_name));
-                mutex_unlock(&parent_dentry->d_inode->i_mutex);
-                dput(parent_dentry);
-
-                if (IS_ERR(dentry)) {
-                        sysfs_put(cur);
-                        return dentry;
-                }
+                mutex_unlock(&parent->d_inode->i_mutex);
+                dput(parent);
 
-                mutex_lock(&sysfs_mutex);
-                spin_lock(&sysfs_assoc_lock);
-
-                /* This, again, can happen if tree structure has
-                 * changed and we looked up the wrong thing.  Restart.
-                 */
-                if (cur->s_dentry != dentry) {
-                        dput(dentry);
-                        sysfs_put(cur);
-                        goto restart1;
-                }
-
-                spin_unlock(&sysfs_assoc_lock);
-
-                sysfs_put(cur);
+                if (IS_ERR(dentry))
+                        break;
         }
-
-        mutex_unlock(&sysfs_mutex);
         return dentry;
 }