On Mon, 6 Oct 2025 12:47:45 +0200
Greg KH [off-list ref] wrote:

(I've had to trim the 'To' list to send this...)

quoted

On Fri, Oct 03, 2025 at 12:59:54PM +0000, Eliav Farber wrote:

quoted

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 <redacted>
Cc: Lorenzo Stoakes <redacted>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Eliav Farber <redacted>

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)
      |                                                             ^~~~

That constant seems to get (renamed and) changed to 32 in a later patch.
I'm not sure of the rational for the min() at all.
I think THREAD_SIZE is the size of the kernel stack? Or at least related to it.
The default seems to be 8k on x86-64 and 4k or 8k on i386.
So it is pretty much always going to be 96.

Linus added MIN() that can be used for array sizes.
But I'd guess this could just be changed to 32 - need to ask the erofs guys.

Changing the definition of Z_EROFS_VMAP_ONSTACK_PAGES to use
  MIN_T(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U)
instead of
  min_t(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U).
fixes the build failure.

This aligns with the change made in upstream commit
4477b39c32fd("minmax: add a few more MIN_T/MAX_T users"):
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4477b39c32fdc03363affef4b11d48391e6dc9ff

---
Regards, Eliav