1 files changed, 122 insertions, 1 deletions

diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 9c04053a8f1c..21620054e1c4 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -1042,13 +1042,134 @@ error_inode:
 	goto out;
 }
 
+static void vfat_exchange_ipos(struct inode *old_inode, struct inode *new_inode,
+			       loff_t old_i_pos, loff_t new_i_pos)
+{
+	fat_detach(old_inode);
+	fat_detach(new_inode);
+	fat_attach(old_inode, new_i_pos);
+	fat_attach(new_inode, old_i_pos);
+}
+
+static void vfat_move_nlink(struct inode *src, struct inode *dst)
+{
+	drop_nlink(src);
+	inc_nlink(dst);
+}
+
+static int vfat_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
+				struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct buffer_head *old_dotdot_bh = NULL, *new_dotdot_bh = NULL;
+	struct msdos_dir_entry *old_dotdot_de = NULL, *new_dotdot_de = NULL;
+	struct inode *old_inode, *new_inode;
+	struct timespec64 ts = current_time(old_dir);
+	loff_t old_i_pos, new_i_pos;
+	int err, corrupt = 0;
+	struct super_block *sb = old_dir->i_sb;
+
+	old_inode = d_inode(old_dentry);
+	new_inode = d_inode(new_dentry);
+
+	/* Acquire super block lock for the operation to be atomic */
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	/* if directories are not the same, get ".." info to update */
+	if (old_dir != new_dir) {
+		err = vfat_get_dotdot_de(old_inode, &old_dotdot_bh,
+					 &old_dotdot_de);
+		if (err)
+			goto out;
+
+		err = vfat_get_dotdot_de(new_inode, &new_dotdot_bh,
+					 &new_dotdot_de);
+		if (err)
+			goto out;
+	}
+
+	old_i_pos = MSDOS_I(old_inode)->i_pos;
+	new_i_pos = MSDOS_I(new_inode)->i_pos;
+
+	vfat_exchange_ipos(old_inode, new_inode, old_i_pos, new_i_pos);
+
+	err = vfat_sync_ipos(old_dir, new_inode);
+	if (err)
+		goto error_exchange;
+	err = vfat_sync_ipos(new_dir, old_inode);
+	if (err)
+		goto error_exchange;
+
+	/* update ".." directory entry info */
+	if (old_dotdot_de) {
+		err = vfat_update_dotdot_de(new_dir, old_inode, old_dotdot_bh,
+					    old_dotdot_de);
+		if (err)
+			goto error_old_dotdot;
+	}
+	if (new_dotdot_de) {
+		err = vfat_update_dotdot_de(old_dir, new_inode, new_dotdot_bh,
+					    new_dotdot_de);
+		if (err)
+			goto error_new_dotdot;
+	}
+
+	/* if cross directory and only one is a directory, adjust nlink */
+	if (!old_dotdot_de != !new_dotdot_de) {
+		if (old_dotdot_de)
+			vfat_move_nlink(old_dir, new_dir);
+		else
+			vfat_move_nlink(new_dir, old_dir);
+	}
+
+	vfat_update_dir_metadata(old_dir, &ts);
+	/* if directories are not the same, update new_dir as well */
+	if (old_dir != new_dir)
+		vfat_update_dir_metadata(new_dir, &ts);
+
+out:
+	brelse(old_dotdot_bh);
+	brelse(new_dotdot_bh);
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+
+	return err;
+
+error_new_dotdot:
+	if (new_dotdot_de) {
+		corrupt |= vfat_update_dotdot_de(new_dir, new_inode,
+						 new_dotdot_bh, new_dotdot_de);
+	}
+
+error_old_dotdot:
+	if (old_dotdot_de) {
+		corrupt |= vfat_update_dotdot_de(old_dir, old_inode,
+						 old_dotdot_bh, old_dotdot_de);
+	}
+
+error_exchange:
+	vfat_exchange_ipos(old_inode, new_inode, new_i_pos, old_i_pos);
+	corrupt |= vfat_sync_ipos(new_dir, new_inode);
+	corrupt |= vfat_sync_ipos(old_dir, old_inode);
+
+	if (corrupt < 0) {
+		fat_fs_error(new_dir->i_sb,
+			     "%s: Filesystem corrupted (i_pos %lld, %lld)",
+			     __func__, old_i_pos, new_i_pos);
+	}
+	goto out;
+}
+
 static int vfat_rename2(struct user_namespace *mnt_userns, struct inode *old_dir,
 			struct dentry *old_dentry, struct inode *new_dir,
 			struct dentry *new_dentry, unsigned int flags)
 {
-	if (flags & ~RENAME_NOREPLACE)
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 		return -EINVAL;
 
+	if (flags & RENAME_EXCHANGE) {
+		return vfat_rename_exchange(old_dir, old_dentry,
+					    new_dir, new_dentry);
+	}
+
 	/* VFS already handled RENAME_NOREPLACE, handle it as a normal rename */
 	return vfat_rename(old_dir, old_dentry, new_dir, new_dentry);
 }