On Fri, Oct 02, 2020 at 03:36:14AM +0900, Naohiro Aota wrote:
> 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: Johannes Thumshirn <jthumshirn@xxxxxxx>
> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
> ---
> fs/btrfs/ioctl.c | 3 +++
> fs/btrfs/zoned.c | 6 ++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index ab408a23ba32..5d592da4e2ff 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -91,6 +91,9 @@ struct btrfs_ioctl_send_args_32 {
> static unsigned int btrfs_mask_fsflags_for_type(struct inode *inode,
> unsigned int flags)
> {
> + if (btrfs_fs_incompat(btrfs_sb(inode->i_sb), ZONED))
> + flags &= ~FS_NOCOW_FL;
> +
This can't be inside the function, the 'type' here is for inode that
does not know anything about zoned mode. The right place is after
check_fsflags in btrfs_ioctl_setflags in a helper like:
ret = check_fsflags_compatible(fs_info, flags));
if (ret)
goto out_unlock;
and check_fsflags_compatible checks for zoned mode and NOCOW and returns
-EPERM, not silently unmasking it.
> if (S_ISDIR(inode->i_mode))
> return flags;
> else if (S_ISREG(inode->i_mode))
