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From: Andreas Hindborg <nmi@metaspace.dk>
To: Keith Busch <kbusch@kernel.org>
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Subject: Re: [PATCH v4 2/3] rust: block: add rnull, Rust null_blk
 implementation
In-Reply-To: <ZlsvHV6y4DEdC8ja@kbusch-mbp.dhcp.thefacebook.com> (Keith Busch's
	message of "Sat, 1 Jun 2024 08:24:29 -0600")
References: <20240601134005.621714-1-nmi@metaspace.dk>
	<20240601134005.621714-3-nmi@metaspace.dk>
	<ZlsvHV6y4DEdC8ja@kbusch-mbp.dhcp.thefacebook.com>
Date: Sat, 01 Jun 2024 17:36:20 +0200
Message-ID: <875xusoetn.fsf@metaspace.dk>
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MIME-Version: 1.0
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Keith Busch <kbusch@kernel.org> writes:

> On Sat, Jun 01, 2024 at 03:40:04PM +0200, Andreas Hindborg wrote:
>> +impl kernel::Module for NullBlkModule {
>> +    fn init(_module: &'static ThisModule) -> Result<Self> {
>> +        pr_info!("Rust null_blk loaded\n");
>> +        let tagset = Arc::pin_init(TagSet::try_new(1, 256, 1), flags::GFP_KERNEL)?;
>> +
>> +        let disk = {
>> +            let block_size: u16 = 4096;
>> +            if block_size % 512 != 0 || !(512..=4096).contains(&block_size) {
>> +                return Err(kernel::error::code::EINVAL);
>> +            }
>
> You've set block_size to the literal 4096, then validate its value
> immediately after? Am I missing some way this could ever be invalid?

Good catch. It is because I have a patch in the outbound queue that allows setting
the block size via a module parameter. The module parameter patch is not
upstream yet. Once I have that up, I will send the patch with the block
size config.

Do you think it is OK to have this redundancy? It would only be for a
few cycles.

Best regards,
Andreas