From: Greg KH <gregkh@linuxfoundation•org>
To: Eliav Farber <farbere@amazon•com>
Cc: jdike@addtoit•com, richard@nod•at,
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Linus Torvalds <torvalds@linux-foundation•org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle•com>
Subject: Re: [PATCH v2 07/19 5.15.y] minmax: simplify and clarify min_t()/max_t() implementation
Date: Mon, 6 Oct 2025 12:47:45 +0200 [thread overview]
Message-ID: <2025100648-capable-register-101b@gregkh> (raw)
In-Reply-To: <20251003130006.41681-8-farbere@amazon.com>
On Fri, Oct 03, 2025 at 12:59:54PM +0000, Eliav Farber wrote:
> From: Linus Torvalds <torvalds@linux-foundation•org>
>
> [ Upstream commit 017fa3e89187848fd056af757769c9e66ac3e93d ]
>
> This simplifies the min_t() and max_t() macros by no longer making them
> work in the context of a C constant expression.
>
> That means that you can no longer use them for static initializers or
> for array sizes in type definitions, but there were only a couple of
> such uses, and all of them were converted (famous last words) to use
> MIN_T/MAX_T instead.
>
> Cc: David Laight <David.Laight@aculab•com>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle•com>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation•org>
> Signed-off-by: Eliav Farber <farbere@amazon•com>
Eliav, your testing infrastructure needs some work, this patch breaks
the build on this kernel tree:
In file included from ./include/linux/kernel.h:16,
from ./include/linux/list.h:9,
from ./include/linux/wait.h:7,
from ./include/linux/wait_bit.h:8,
from ./include/linux/fs.h:6,
from fs/erofs/internal.h:10,
from fs/erofs/zdata.h:9,
from fs/erofs/zdata.c:6:
fs/erofs/zdata.c: In function ‘z_erofs_decompress_pcluster’:
fs/erofs/zdata.h:185:61: error: ISO C90 forbids variable length array ‘pages_onstack’ [-Werror=vla]
185 | min_t(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U)
| ^~~~
./include/linux/minmax.h:49:23: note: in definition of macro ‘__cmp_once_unique’
49 | ({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
| ^
./include/linux/minmax.h:164:27: note: in expansion of macro ‘__cmp_once’
164 | #define min_t(type, x, y) __cmp_once(min, type, x, y)
| ^~~~~~~~~~
fs/erofs/zdata.h:185:9: note: in expansion of macro ‘min_t’
185 | min_t(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U)
| ^~~~~
fs/erofs/zdata.c:847:36: note: in expansion of macro ‘Z_EROFS_VMAP_ONSTACK_PAGES’
847 | struct page *pages_onstack[Z_EROFS_VMAP_ONSTACK_PAGES];
| ^~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
I'll drop this whole series, please do a bit more testing before sending
out a new version.
thanks,
greg k-h
next prev parent reply other threads:[~2025-10-06 10:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-03 12:59 [PATCH v2 00/19 5.15.y] Backport minmax.h updates from v6.17-rc7 Eliav Farber
2025-10-03 12:59 ` [PATCH v2 01/19 5.15.y] minmax: add in_range() macro Eliav Farber
2025-10-03 12:59 ` [PATCH v2 02/19 5.15.y] minmax: Introduce {min,max}_array() Eliav Farber
2025-10-03 12:59 ` [PATCH v2 03/19 5.15.y] minmax: deduplicate __unconst_integer_typeof() Eliav Farber
2025-10-03 12:59 ` [PATCH v2 04/19 5.15.y] minmax: fix indentation of __cmp_once() and __clamp_once() Eliav Farber
2025-10-03 12:59 ` [PATCH v2 05/19 5.15.y] minmax: avoid overly complicated constant expressions in VM code Eliav Farber
2025-10-03 12:59 ` [PATCH v2 06/19 5.15.y] minmax: add a few more MIN_T/MAX_T users Eliav Farber
2025-10-03 12:59 ` [PATCH v2 07/19 5.15.y] minmax: simplify and clarify min_t()/max_t() implementation Eliav Farber
2025-10-06 10:47 ` Greg KH [this message]
2025-10-06 20:35 ` David Laight
2025-10-07 20:43 ` Farber, Eliav
2025-10-03 12:59 ` [PATCH v2 08/19 5.15.y] minmax: make generic MIN() and MAX() macros available everywhere Eliav Farber
2025-10-03 12:59 ` [PATCH v2 09/19 5.15.y] minmax: don't use max() in situations that want a C constant expression Eliav Farber
2025-10-03 12:59 ` [PATCH v2 10/19 5.15.y] minmax: simplify min()/max()/clamp() implementation Eliav Farber
2025-10-03 12:59 ` [PATCH v2 11/19 5.15.y] minmax: improve macro expansion and type checking Eliav Farber
2025-10-03 12:59 ` [PATCH v2 12/19 5.15.y] minmax: fix up min3() and max3() too Eliav Farber
2025-10-03 13:00 ` [PATCH v2 13/19 5.15.y] minmax.h: add whitespace around operators and after commas Eliav Farber
2025-10-03 13:00 ` [PATCH v2 14/19 5.15.y] minmax.h: update some comments Eliav Farber
2025-10-03 13:00 ` [PATCH v2 15/19 5.15.y] minmax.h: reduce the #define expansion of min(), max() and clamp() Eliav Farber
2025-10-03 13:00 ` [PATCH v2 16/19 5.15.y] minmax.h: use BUILD_BUG_ON_MSG() for the lo < hi test in clamp() Eliav Farber
2025-10-03 13:00 ` [PATCH v2 17/19 5.15.y] minmax.h: move all the clamp() definitions after the min/max() ones Eliav Farber
2025-10-03 13:00 ` [PATCH v2 18/19 5.15.y] minmax.h: simplify the variants of clamp() Eliav Farber
2025-10-03 13:00 ` [PATCH v2 19/19 5.15.y] minmax.h: remove some #defines that are only expanded once Eliav Farber
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