linux-kernel - Re: [PATCH] crypto: hash - Make HASH_MAX

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Message-ID: <CAHk-=wg1okLMc41jaxS+WRXigw7Fu+OUc6QsnL+BbvYAGTdZYA@mail.gmail.com>
Date: Mon, 11 Aug 2025 10:10:44 +0300
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Vegard Nossum <vegard.nossum@...cle.com>, "David S. Miller" <davem@...emloft.net>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH] crypto: hash - Make HASH_MAX_DESCSIZE a bit more obvious

On Mon, 11 Aug 2025 at 07:44, Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> The patch below should make the constant a bit more obvious.

Indeed.

It would be good to maybe minimize the on-stack max-sized allocations,
but that's a separate issue. Several hundred bytes is a noticeable
part of the stack, and it's not always clear that it's a shallow stack
with not a lot else going on..

(I just randomly picked the btrfs csum hash to look at, which can
apparently be one of crc32c / xxhash64 / sha256 or blake2b, and which
is then used at bio submission time, and I wouldn't be surprised if it
probably has a pretty deep stack at that point already).

Oh well.

          Linus