Re: [PATCH] btrfs-progs: subvolume: Add warning on deleting default subvolume

[Su Yue <l@damenly.su>]

On Mon 28 Sep 2020 at 23:07, Sidong Yang <realwakka@gmail.com> 
wrote:

> This patch add warning messages when user try to delete default
> subvolume. When deleting default subvolume, kernel will not 
> allow and
> make error message on syslog. but there is only message that 
> permission
> denied on userspace. User can be noticed the reason by this 
> warning message.
>
> This patch implements github issue.
> https://github.com/kdave/btrfs-progs/issues/274
>
> Signed-off-by: Sidong Yang <realwakka@gmail.com>
> ---
>  cmds/subvolume.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/cmds/subvolume.c b/cmds/subvolume.c
> index 2020e486..0cdf7a68 100644
> --- a/cmds/subvolume.c
> +++ b/cmds/subvolume.c
> @@ -264,6 +264,7 @@ static int cmd_subvol_delete(const struct 
> cmd_struct *cmd,
>  	struct seen_fsid *seen_fsid_hash[SEEN_FSID_HASH_SIZE] = { 
>  NULL, };
>  	enum { COMMIT_AFTER = 1, COMMIT_EACH = 2 };
>  	enum btrfs_util_error err;
> +	uint64_t default_subvol_id = 0, target_subvol_id = 0;
>
>  	optind = 0;
>  	while (1) {
> @@ -360,6 +361,25 @@ again:
>  		goto out;
>  	}
>
> +	err = btrfs_util_get_default_subvolume_fd(fd, 
> &default_subvol_id);
> +	if (fd < 0) {
>
Should it be
"     if (err) { 
|
         error_btrfs_util(err);
         ...
"?

> +		ret = 1;
> +		goto out;
> +	}
> +
> +	if (subvolid > 0)
> +		target_subvol_id = subvolid;
> +	else {
> +		err = btrfs_util_subvolume_id(path, &target_subvol_id);
> +		if (fd < 0) {
>
And here.

> +			ret = 1;
> +			goto out;
> +		}
> +	}
> +
> +	if (target_subvol_id == default_subvol_id)
> +		warning("trying to delete default subvolume.");
> +
>  	pr_verbose(MUST_LOG, "Delete subvolume (%s): ",
>  		commit_mode == COMMIT_EACH ||
>  		(commit_mode == COMMIT_AFTER && cnt + 1 == argc) ?