Re: [PATCH] btrfs-progs: warn users about the possible dangers of check --repair

[Nikolay Borisov <nborisov@suse.com>]

On 16.10.19 г. 17:05 ч., Johannes Thumshirn wrote:
> The manual page of btrfsck clearly states 'btrfs check --repair' is a
> dangerous operation.
> 
> Although this warning is in place users do not read the manual page and/or
> are used to the behaviour of fsck utilities which repair the filesystem,
> and thus potentially cause harm.
> 
> Similar to 'btrfs balance' without any filters, add a warning and a
> countdown, so users can bail out before eventual corrupting the filesystem
> more than it already is.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> ---
>  check/main.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/check/main.c b/check/main.c
> index fd05430c1f51..acded927281a 100644
> --- a/check/main.c
> +++ b/check/main.c
> @@ -9970,6 +9970,23 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
>  		exit(1);
>  	}
>  
> +	if (repair) {
> +		int delay = 10;
> +		printf("WARNING:\n\n");
> +		printf("\tDo not use --repair unless you are advised to do so by a developer\n");
> +		printf("\tor an experienced user, and then only after having accepted that no\n");
> +		printf("\tfsck successfully repair all types of filesystem corruption. Eg.\n");
> +		printf("\tsome other software or hardware bugs can fatally damage a volume.\n");

nit: The word 'other' here is redundant, no ?

> +		printf("\tThe operation will start in %d seconds.\n", delay);
> +		printf("\tUse Ctrl-C to stop it.\n");
> +		while (delay) {
> +			printf("%2d", delay--);
> +			fflush(stdout);
> +			sleep(1);
> +		}

That's a long winded way to have a simple for  loop that prints 10 dots,
1 second apart.  IMO a better use experience would be to ask the user to
confirm and if the '-f' options i passed don't bother printing the
warning at all.

> +		printf("\nStarting repair.\n");
> +	}
> +
>  	/*
>  	 * experimental and dangerous
>  	 */
>