Re: [f2fs-dev] [PATCH 3/3] libf2fs: don't allow mkfs / fsck on zoned NPO2

[Damien Le Moal via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On Tue, 2022-04-12 at 13:27 +0200, Pankaj Raghav wrote:
> From: Luis Chamberlain <mcgrof@kernel.org>
> 
> f2fs currently only work with zoned storage devices with a zone
> size which is a power of 2 (PO2). So check if a non-power of 2
> zone is device is found, and if so disallow its use. This prevents
> users from incorrectly using these devices.
> 
> This is a non-issue today give today's kernel does not allow NPO2
> zon devices to exist. But these devices do exist, and so proactively
> put a stop-gap measure in place to prevent the from being assumed
> to be used.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  lib/libf2fs.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/libf2fs.c b/lib/libf2fs.c
> index 8fad1d7..a13ba32 100644
> --- a/lib/libf2fs.c
> +++ b/lib/libf2fs.c
> @@ -882,6 +882,11 @@ static int open_check_fs(char *path, int flag)
>  	return open(path, O_RDONLY | flag);
>  }
>  
> +static int is_power_of_2(unsigned long n)
> +{
> +	return (n != 0 && ((n & (n - 1)) == 0));
> +}
> +
>  int get_device_info(int i)
>  {
>  	int32_t fd = 0;
> @@ -1043,6 +1048,13 @@ int get_device_info(int i)
>  			return -1;
>  		}
>  
> +		if (!dev->zone_size || !is_power_of_2(dev->zone_size)) {
> +			MSG(0, "\tError: zoned: illegal zone size %lu (not a power of 2)\n",
> +					dev->zone_size);

The message should be different for the !dev->zone_size case since that
would be an error.

> +			free(stat_buf);
> +			return -1;
> +		}
> +
>  		/*
>  		 * Check zone configuration: for the first disk of a
>  		 * multi-device volume, conventional zones are needed.

Of the 3 patches of this series, this one is the only one that makes sense
to me. I fail to see how the first 2 patches improve things.

-- 
Damien Le Moal
Western Digital Research


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