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Date:   Tue, 5 Feb 2019 20:06:37 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Dennis Zhou <dennis@kernel.org>
Cc:     David Sterba <dsterba@suse.com>,
        Josef Bacik <josef@toxicpanda.com>, Chris Mason <clm@fb.com>,
        Omar Sandoval <osandov@osandov.com>,
        Nick Terrell <terrelln@fb.com>,
        Nikolay Borisov <nborisov@suse.com>, kernel-team@fb.com,
        linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/12] btrfs: change set_level() to bound the level
 passed in
Message-ID: <20190205190636.GZ2900@twin.jikos.cz>
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References: <20190204202008.51652-1-dennis@kernel.org>
 <20190204202008.51652-10-dennis@kernel.org>
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On Mon, Feb 04, 2019 at 03:20:05PM -0500, Dennis Zhou wrote:
> -unsigned int btrfs_compress_str2level(const char *str)
> +unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
>  {
> -	if (strncmp(str, "zlib", 4) != 0)
> +	unsigned int level;
> +	int ret;
> +
> +	if (!type)
>  		return 0;
>  
> -	/* Accepted form: zlib:1 up to zlib:9 and nothing left after the number */
> -	if (str[4] == ':' && '1' <= str[5] && str[5] <= '9' && str[6] == 0)
> -		return str[5] - '0';
> +	if (str[0] == ':') {
> +		ret = kstrtouint(str + 1, 10, &level);

The docs kstrtouint of say that initial + is also accepted, I'd rather
keep the level specification strict, ie. no "zlib:+3" and no garbage
after the number.

The validation is currently missing but I think we should catch levels
out of range during mount/remount. The fallback to default is a safety
but wrong specification should be communicated to the user early.