btrfs: disallow NODATACOW in ZONED mode

NODATACOW implies overwriting the file data on a device, which is
impossible in sequential required zones. Disable NODATACOW globally with
mount option and per-file NODATACOW attribute by masking FS_NOCOW_FL.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -193,6 +193,15 @@ static int check_fsflags(unsigned int old_flags, unsigned int flags)
 	return 0;
 }
 
+static int check_fsflags_compatible(struct btrfs_fs_info *fs_info,
+				    unsigned int flags)
+{
+	if (btrfs_is_zoned(fs_info) && (flags & FS_NOCOW_FL))
+		return -EPERM;
+
+	return 0;
+}
+
 static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 {
 	struct inode *inode = file_inode(file);
@@ -230,6 +239,10 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	if (ret)
 		goto out_unlock;
 
+	ret = check_fsflags_compatible(fs_info, fsflags);
+	if (ret)
+		goto out_unlock;
+
 	binode_flags = binode->flags;
 	if (fsflags & FS_SYNC_FL)
 		binode_flags |= BTRFS_INODE_SYNC;

fs/btrfs/zoned.c

@@ -274,5 +274,10 @@ int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
 		return -EINVAL;
 	}
 
+	if (btrfs_test_opt(info, NODATACOW)) {
+		btrfs_err(info, "zoned: NODATACOW not supported");
+		return -EINVAL;
+	}
+
 	return 0;
 }