Re: [PATCH 3/5] mm/parisc: constify ptep_get() argument

On 2026-07-25 12:27 p.m., Helge Deller wrote:

On 7/24/26 17:48, Usama Arif wrote:

quoted

On 24/07/2026 16:32, Pedro Falcato wrote:

quoted

On Fri, Jul 24, 2026 at 04:03:44PM +0100, Usama Arif wrote:

quoted

On 24/07/2026 15:14, Matthew Wilcox wrote:

quoted

On Fri, Jul 24, 2026 at 02:36:59PM +0100, Usama Arif wrote:

quoted

On 24/07/2026 11:20, Pedro Falcato wrote:

quoted

ptep_get() does not need write access to the PTE.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
  arch/parisc/include/asm/pgtable.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

hmm I think you might break build bisectibility if
you separate out the patches, you should squash patch 3 and 4,
with patch 1.

I don't see how this breaks bisectability.  Can you elaborate on what
you think would break?

Patch 1 does:

-static inline pte_t ptep_get_lockless(pte_t *ptep)
+static inline pte_t ptep_get_lockless(const pte_t *ptep)
  {
      return ptep_get(ptep);
  }


ptep_get() takes a non-const arg till patch 3 for example for parsic.
I don't think you can pass a const variable to non const function arg?

So parsic won't compile in patch 1 and 2, powerprc wont compile
for patches 1, 2 and 3..

Aha, yes, nice catch! I'll have to rethink that. Maybe squashing the patches
would be the cleanest way forward.

Yes, squashing is the simplest way forward.

quoted

FWIW, the vast majority of architectures aren't doing funny things on
ptep_get(). E.g PA-RISC, loongarch only define these so they can use it in
their own asm/pgtable.h. I'd really like to delete these but I can't tell
if they are *actually* required.

Ah maybe there is something in git history on why it was needed?

If not, hopefully someone from the arch lists could clarify..

I tried to remove ptep_get() and ptep_test_and_clear_young() from
arch/parisc/include/asm/pgtable.h, but this then triggers compile errors:

 CC      arch/parisc/kernel/asm-offsets.s
In file included from /home/cvs/parisc/git-kernel/linus-linux-2.6/include/linux/mm.h:31,
                 from /home/cvs/parisc/git-kernel/linus-linux-2.6/include/linux/pid_namespace.h:7,
                 from /home/cvs/parisc/git-kernel/linus-linux-2.6/include/linux/ptrace.h:10,
                 from /home/cvs/parisc/git-kernel/linus-linux-2.6/arch/parisc/kernel/asm-offsets.c:21:
/home/cvs/parisc/git-kernel/linus-linux-2.6/include/linux/pgtable.h: In function ‘clear_young_dirty_ptes’:
/home/cvs/parisc/git-kernel/linus-linux-2.6/include/linux/pgtable.h:683:25: error: implicit declaration of function ‘ptep_test_and_clear_young’;
did you mean ‘pmdp_test_and_clear_young’? [-Wimplicit-function-declaration]
  683 |                         ptep_test_and_clear_young(vma, addr, ptep);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~
      |                         pmdp_test_and_clear_young

So, I think the answer is, that the local copy of ptep_get() is used in the parisc implementation of
ptep_test_and_clear_young() function.

Switching to the default include/linux/pgtable.h seems not easy doable....

Did you remove define for __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG in parisc version of pgtable.h?

Dave
-- 
John David Anglin  dave.anglin@bell.net