reiserfs: Avoid touching renamed directory if parent does not change

The VFS will not be locking moved directory if its parent does not
change. Change reiserfs rename code to avoid touching renamed directory
if its parent does not change as without locking that can corrupt the
filesystem.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/reiserfs/namei.c

@@ -1324,8 +1324,8 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 	struct inode *old_inode, *new_dentry_inode;
 	struct reiserfs_transaction_handle th;
 	int jbegin_count;
-	umode_t old_inode_mode;
 	unsigned long savelink = 1;
+	bool update_dir_parent = false;
 
 	if (flags & ~RENAME_NOREPLACE)
 		return -EINVAL;
@@ -1375,8 +1375,7 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 		return -ENOENT;
 	}
 
-	old_inode_mode = old_inode->i_mode;
-	if (S_ISDIR(old_inode_mode)) {
+	if (S_ISDIR(old_inode->i_mode)) {
 		/*
 		 * make sure that directory being renamed has correct ".."
 		 * and that its new parent directory has not too many links
@@ -1389,24 +1388,28 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 			}
 		}
 
-		/*
-		 * directory is renamed, its parent directory will be changed,
-		 * so find ".." entry
-		 */
-		dot_dot_de.de_gen_number_bit_string = NULL;
-		retval =
-		    reiserfs_find_entry(old_inode, "..", 2, &dot_dot_entry_path,
+		if (old_dir != new_dir) {
+			/*
+			 * directory is renamed, its parent directory will be
+			 * changed, so find ".." entry
+			 */
+			dot_dot_de.de_gen_number_bit_string = NULL;
+			retval =
+			    reiserfs_find_entry(old_inode, "..", 2,
+					&dot_dot_entry_path,
 					&dot_dot_de);
-		pathrelse(&dot_dot_entry_path);
-		if (retval != NAME_FOUND) {
-			reiserfs_write_unlock(old_dir->i_sb);
-			return -EIO;
-		}
+			pathrelse(&dot_dot_entry_path);
+			if (retval != NAME_FOUND) {
+				reiserfs_write_unlock(old_dir->i_sb);
+				return -EIO;
+			}
 
-		/* inode number of .. must equal old_dir->i_ino */
-		if (dot_dot_de.de_objectid != old_dir->i_ino) {
-			reiserfs_write_unlock(old_dir->i_sb);
-			return -EIO;
+			/* inode number of .. must equal old_dir->i_ino */
+			if (dot_dot_de.de_objectid != old_dir->i_ino) {
+				reiserfs_write_unlock(old_dir->i_sb);
+				return -EIO;
+			}
+			update_dir_parent = true;
 		}
 	}
 
@@ -1486,7 +1489,7 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 
 		reiserfs_prepare_for_journal(old_inode->i_sb, new_de.de_bh, 1);
 
-		if (S_ISDIR(old_inode->i_mode)) {
+		if (update_dir_parent) {
 			if ((retval =
 			     search_by_entry_key(new_dir->i_sb,
 						 &dot_dot_de.de_entry_key,
@@ -1534,14 +1537,14 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 							 new_de.de_bh);
 			reiserfs_restore_prepared_buffer(old_inode->i_sb,
 							 old_de.de_bh);
-			if (S_ISDIR(old_inode_mode))
+			if (update_dir_parent)
 				reiserfs_restore_prepared_buffer(old_inode->
 								 i_sb,
 								 dot_dot_de.
 								 de_bh);
 			continue;
 		}
-		if (S_ISDIR(old_inode_mode)) {
+		if (update_dir_parent) {
 			if (item_moved(&dot_dot_ih, &dot_dot_entry_path) ||
 			    !entry_points_to_object("..", 2, &dot_dot_de,
 						    old_dir)) {
@@ -1559,7 +1562,7 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 			}
 		}
 
-		RFALSE(S_ISDIR(old_inode_mode) &&
+		RFALSE(update_dir_parent &&
 		       !buffer_journal_prepared(dot_dot_de.de_bh), "");
 
 		break;
@@ -1592,11 +1595,12 @@ static int reiserfs_rename(struct mnt_idmap *idmap,
 		savelink = new_dentry_inode->i_nlink;
 	}
 
-	if (S_ISDIR(old_inode_mode)) {
+	if (update_dir_parent) {
 		/* adjust ".." of renamed directory */
 		set_ino_in_dir_entry(&dot_dot_de, INODE_PKEY(new_dir));
 		journal_mark_dirty(&th, dot_dot_de.de_bh);
-
+	}
+	if (S_ISDIR(old_inode->i_mode)) {
 		/*
 		 * there (in new_dir) was no directory, so it got new link
 		 * (".."  of renamed directory)