linux-kernel - Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wicdsz3bvy9g7RJ_XvugjxAT0XDitwTQLZmxq40JtHbzg@mail.gmail.com>
Date: Sun, 28 Jul 2024 15:22:58 -0700
From: Linus Torvalds <torvalds@...uxfoundation.org>
To: David Laight <David.Laight@...lab.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, 
	"Matthew Wilcox (Oracle)" <willy@...radead.org>, Christoph Hellwig <hch@...radead.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, Arnd Bergmann <arnd@...nel.org>, 
	"Jason@...c4.com" <Jason@...c4.com>, "pedro.falcato@...il.com" <pedro.falcato@...il.com>, 
	Mateusz Guzik <mjguzik@...il.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together

On Sun, 28 Jul 2024 at 15:14, David Laight <David.Laight@...lab.com> wrote:
>
> Ok, but those can't be used as array sizes or constants.
> So the temporaries don't matter.

No, mut I don't want the insane size explosion from unnecessarily just
forcing it to use min()/max().

> Don't they just work with min() - if not where is the signednes mismatch?

David - this whole discussion is BECAUSE THESE THINGS ARE A TOTAL
DISASTER WHEN USED IN DEEP MACRO EXPANSION.

So no. It does not work - because core macros like HUGETLB_PAGE_ORDER
end up being used deep in the VM layer, and I don't want to see
another stupid multi-ten-kB line just because min() is such a pig.

End result: I'm going to make the rule be that when you do macro
definitions using constants, then "MIN()/MAX()" is preferable simply
because it avoids the insane expansion noise.

Then in normal *code* you should use min() and max(). But not for
things like macro "constants" even if those constants end up being
some computed thing.

          Linus