ovl: narrow locking in ovl_cleanup_index()

ovl_cleanup_index() takes a lock on the directory and then does a lookup
and possibly one of two different cleanups.
This patch narrows the locking to use the _unlocked() versions of the
lookup and one cleanup, and just takes the lock for the other cleanup.

A subsequent patch will take the lock into the cleanup.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250716004725.1206467-12-neil@brown.name
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/overlayfs/util.c

@@ -1078,7 +1078,6 @@ static void ovl_cleanup_index(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
-	struct inode *dir = indexdir->d_inode;
 	struct dentry *lowerdentry = ovl_dentry_lower(dentry);
 	struct dentry *upperdentry = ovl_dentry_upper(dentry);
 	struct dentry *index = NULL;
@@ -1114,21 +1113,22 @@ static void ovl_cleanup_index(struct dentry *dentry)
 		goto out;
 	}
 
-	inode_lock_nested(dir, I_MUTEX_PARENT);
-	index = ovl_lookup_upper(ofs, name.name, indexdir, name.len);
+	index = ovl_lookup_upper_unlocked(ofs, name.name, indexdir, name.len);
 	err = PTR_ERR(index);
 	if (IS_ERR(index)) {
 		index = NULL;
 	} else if (ovl_index_all(dentry->d_sb)) {
 		/* Whiteout orphan index to block future open by handle */
-		err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
-					       indexdir, index);
+		err = ovl_parent_lock(indexdir, index);
+		if (!err) {
+			err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
+						       indexdir, index);
+			ovl_parent_unlock(indexdir);
+		}
 	} else {
 		/* Cleanup orphan index entries */
-		err = ovl_cleanup(ofs, dir, index);
+		err = ovl_cleanup_unlocked(ofs, indexdir, index);
 	}
-
-	inode_unlock(dir);
 	if (err)
 		goto fail;