linux-kernel - Re: [PATCH v2 3/3] nbd: correct the maximum value for discard sectors

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Message-ID: <ZrRrzTKiAVXNItFo@pc220518.home.grep.be>
Date: Thu, 8 Aug 2024 08:55:09 +0200
From: Wouter Verhelst <w@...r.be>
To: Josef Bacik <josef@...icpanda.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
	nbd@...er.debian.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] nbd: correct the maximum value for discard sectors

Hi Josef,

On Wed, Aug 07, 2024 at 09:56:25AM -0400, Josef Bacik wrote:
> We use 512 as the "sectors" measurement throughout the block layer, so our limit
> is actually
> 
> UINT32_MAX >> 9
> 
> since we can only send at most UINT32_MAX as our length.  Fix it to be that for
> both patches and you should be good.  Thanks,

My first stab actually used UINT32_MAX, but that didn't compile.

I investigated and found that for the kernel, UINT32_MAX and UINT_MAX
are actually the same, but in order for me to be able to use UINT32_MAX
(or U32_MAX, which is also defined to the same value), I would need
extra includes.

So I'll stick with the UINT_MAX >> SECTOR_SHIFT definition that Damien
suggested.

Thanks,

-- 
     w@...r.{be,co.za}
wouter@...ep.be,fosdem.org,debian.org}

I will have a Tin-Actinium-Potassium mixture, thanks.