ecryptfs: avoid multiple aliases for directories

ecryptfs_lookup_interpose should use d_splice_alias(), not d_add()
(and return struct dentry * rather than int).  Get rid of
redundant dir_inode argument, while we are touching it...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ecryptfs/inode.c

@@ -324,9 +324,8 @@ static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
 /**
  * ecryptfs_lookup_interpose - Dentry interposition for a lookup
  */
-static int ecryptfs_lookup_interpose(struct dentry *dentry,
-				     struct dentry *lower_dentry,
-				     struct inode *dir_inode)
+static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry,
+				     struct dentry *lower_dentry)
 {
 	struct inode *inode, *lower_inode = d_inode(lower_dentry);
 	struct ecryptfs_dentry_info *dentry_info;
@@ -339,11 +338,12 @@ static int ecryptfs_lookup_interpose(struct dentry *dentry,
 		       "to allocate ecryptfs_dentry_info struct\n",
 			__func__);
 		dput(lower_dentry);
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
-	fsstack_copy_attr_atime(dir_inode, d_inode(lower_dentry->d_parent));
+	fsstack_copy_attr_atime(d_inode(dentry->d_parent),
+				d_inode(lower_dentry->d_parent));
 	BUG_ON(!d_count(lower_dentry));
 
 	ecryptfs_set_dentry_private(dentry, dentry_info);
@@ -353,27 +353,25 @@ static int ecryptfs_lookup_interpose(struct dentry *dentry,
 	if (d_really_is_negative(lower_dentry)) {
 		/* We want to add because we couldn't find in lower */
 		d_add(dentry, NULL);
-		return 0;
+		return NULL;
 	}
-	inode = __ecryptfs_get_inode(lower_inode, dir_inode->i_sb);
+	inode = __ecryptfs_get_inode(lower_inode, dentry->d_sb);
 	if (IS_ERR(inode)) {
 		printk(KERN_ERR "%s: Error interposing; rc = [%ld]\n",
 		       __func__, PTR_ERR(inode));
-		return PTR_ERR(inode);
+		return ERR_CAST(inode);
 	}
 	if (S_ISREG(inode->i_mode)) {
 		rc = ecryptfs_i_size_read(dentry, inode);
 		if (rc) {
 			make_bad_inode(inode);
-			return rc;
+			return ERR_PTR(rc);
 		}
 	}
 
 	if (inode->i_state & I_NEW)
 		unlock_new_inode(inode);
-	d_add(dentry, inode);
-
-	return rc;
+	return d_splice_alias(inode, dentry);
 }
 
 /**
@@ -393,17 +391,18 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 	size_t encrypted_and_encoded_name_size;
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;
 	struct dentry *lower_dir_dentry, *lower_dentry;
+	struct dentry *res;
 	int rc = 0;
 
 	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
 	lower_dentry = lookup_one_len_unlocked(ecryptfs_dentry->d_name.name,
 				      lower_dir_dentry,
 				      ecryptfs_dentry->d_name.len);
 	if (IS_ERR(lower_dentry)) {
-		rc = PTR_ERR(lower_dentry);
 		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
-				"[%d] on lower_dentry = [%pd]\n", __func__, rc,
-				ecryptfs_dentry);
+				"[%ld] on lower_dentry = [%pd]\n", __func__,
+				PTR_ERR(lower_dentry), ecryptfs_dentry);
+		res = ERR_CAST(lower_dentry);
 		goto out;
 	}
 	if (d_really_is_positive(lower_dentry))
@@ -421,24 +420,25 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 	if (rc) {
 		printk(KERN_ERR "%s: Error attempting to encrypt and encode "
 		       "filename; rc = [%d]\n", __func__, rc);
+		res = ERR_PTR(rc);
 		goto out;
 	}
 	lower_dentry = lookup_one_len_unlocked(encrypted_and_encoded_name,
 				      lower_dir_dentry,
 				      encrypted_and_encoded_name_size);
 	if (IS_ERR(lower_dentry)) {
-		rc = PTR_ERR(lower_dentry);
 		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
-				"[%d] on lower_dentry = [%s]\n", __func__, rc,
+				"[%ld] on lower_dentry = [%s]\n", __func__,
+				PTR_ERR(lower_dentry),
 				encrypted_and_encoded_name);
+		res = ERR_CAST(lower_dentry);
 		goto out;
 	}
 interpose:
-	rc = ecryptfs_lookup_interpose(ecryptfs_dentry, lower_dentry,
-				       ecryptfs_dir_inode);
+	res = ecryptfs_lookup_interpose(ecryptfs_dentry, lower_dentry);
 out:
 	kfree(encrypted_and_encoded_name);
-	return ERR_PTR(rc);
+	return res;
 }
 
 static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,