Re: [PATCH v2] btrfs-progs: filesystem-resize: make output more readable

[David Sterba <dsterba@suse.cz>]

On Sat, Jan 23, 2021 at 03:37:20PM +0000, Sidong Yang wrote:
> This patch make output of filesystem-resize command more readable and
> give detail information for users. This patch provides more information
> about filesystem like below.
> 
> Before:
> Resize '/mnt' of '1:-1G'
> 
> After:
> Resize device id 1 (/dev/vdb) from 4.00GiB to 3.00GiB
> 
> Signed-off-by: Sidong Yang <realwakka@gmail.com>
> ---
> v2:
>   - print more detailed error
>   - covers all the possibilities format provides
> ---
>  cmds/filesystem.c | 112 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 111 insertions(+), 1 deletion(-)
> 
> diff --git a/cmds/filesystem.c b/cmds/filesystem.c
> index ba2e5928..cec3f380 100644
> --- a/cmds/filesystem.c
> +++ b/cmds/filesystem.c
> @@ -28,6 +28,7 @@
>  #include <linux/limits.h>
>  #include <linux/version.h>
>  #include <getopt.h>
> +#include <limits.h>
>  
>  #include <btrfsutil.h>
>  
> @@ -1074,6 +1075,109 @@ static const char * const cmd_filesystem_resize_usage[] = {
>  	NULL
>  };
>  
> +static int check_resize_args(const char *amount, const char *path) {
> +	struct btrfs_ioctl_fs_info_args fi_args;
> +	struct btrfs_ioctl_dev_info_args *di_args = NULL;
> +	int ret, i, devid = 0, dev_idx = -1;

devid should be u64

> +	const char *res_str = NULL;
> +	char *devstr = NULL, *sizestr = NULL;
> +	u64 new_size = 0, old_size = 0;
> +	int mod = 0;
> +	char amount_dup[BTRFS_VOL_NAME_MAX];

Bffer of a fixed size ...

> +
> +	ret = get_fs_info(path, &fi_args, &di_args);
> +
> +	if (ret) {
> +		error("unable to retrieve fs info");
> +		return 1;
> +	}
> +
> +	if (!fi_args.num_devices) {
> +		error("no devices found");
> +		free(di_args);
> +		return 1;
> +	}
> +
> +	strcpy(amount_dup, amount);

... and strcpy from a user specified buffer, this is from chapter 1 of
how buffer overflows in C work. Please use safe string copy.

> +	devstr = strchr(amount_dup, ':');
> +	if (devstr) {
> +		sizestr = devstr + 1;
> +		*devstr = '\0';
> +		devstr = amount_dup;
> +
> +		errno = 0;
> +		devid = strtoull(devstr, NULL, 10);
> +
> +		if (errno) {
> +			error("failed to parse devid %s", devstr);
> +			free(di_args);
> +			return 1;
> +		}
> +	}
> +
> +	dev_idx = -1;
> +	for(i = 0; i < fi_args.num_devices; i++) {
> +		if (di_args[i].devid == devid) {
> +			dev_idx = i;
> +			break;
> +		}
> +	}
> +
> +	if (dev_idx < 0) {
> +		error("cannot find devid : %d", devid);
> +		free(di_args);
> +		return 1;
> +	}
> +
> +	if (!strcmp(sizestr, "max")) {
> +		res_str = "max";
> +	}
> +	else {
> +		if (sizestr[0] == '-') {
> +			mod = -1;
> +			sizestr++;
> +		} else if (sizestr[0] == '+') {
> +			mod = 1;
> +			sizestr++;
> +		}
> +		new_size = parse_size(sizestr);
> +		if (!new_size) {
> +			error("failed to parse size %s", sizestr);
> +			free(di_args);
> +			return 1;
> +		}
> +		old_size = di_args[dev_idx].total_bytes;
> +
> +		if (mod < 0) {
> +			if (new_size > old_size) {
> +				error("current size is %s which is smaller than %s",
> +				      pretty_size_mode(old_size, UNITS_DEFAULT),
> +				      pretty_size_mode(new_size, UNITS_DEFAULT));
> +				free(di_args);
> +				return 1;
> +			}
> +			new_size = old_size - new_size;
> +		} else if (mod > 0) {
> +			if (new_size > ULLONG_MAX - old_size) {
> +				error("increasing %s is out of range",
> +				      pretty_size_mode(new_size, UNITS_DEFAULT));
> +				free(di_args);
> +				return 1;
> +			}
> +			new_size = old_size + new_size;

This all got me confused, old_size and new_size sound like absolute
numbers for the size but new_size is in fact used as the delta, or the
relative change.

Otherwise looks good.

> +		}
> +		new_size = round_down(new_size, fi_args.sectorsize);
> +		res_str = pretty_size_mode(new_size, UNITS_DEFAULT);
> +	}
> +
> +	printf("Resize device id %d (%s) from %s to %s\n", devid, di_args[dev_idx].path,
> +		pretty_size_mode(di_args[dev_idx].total_bytes, UNITS_DEFAULT),
> +		res_str);
> +
> +	free(di_args);
> +	return 0;
> +}
> +
>  static int cmd_filesystem_resize(const struct cmd_struct *cmd,
>  				 int argc, char **argv)
>  {
> @@ -1139,7 +1243,13 @@ static int cmd_filesystem_resize(const struct cmd_struct *cmd,
>  		return 1;
>  	}
>  
> -	printf("Resize '%s' of '%s'\n", path, amount);
> +	ret = check_resize_args(path, amount);
> +	if (ret != 0) {
> +		close_file_or_dir(fd, dirstream);
> +		return 1;
> +	}
> +
> +
>  	memset(&args, 0, sizeof(args));
>  	strncpy_null(args.name, amount);
>  	res = ioctl(fd, BTRFS_IOC_RESIZE, &args);
> -- 
> 2.25.1