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Mon, 27 Jul 2026 09:14:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Gy7HOo8hZ2r9DwAAD6G6ig (envelope-from ); Mon, 27 Jul 2026 09:14:55 +0000 Date: Mon, 27 Jul 2026 10:14:54 +0100 From: Pedro Falcato To: Helge Deller Cc: John David Anglin , Usama Arif , Helge Deller , Matthew Wilcox , Andrew Morton , David Hildenbrand , Catalin Marinas , Will Deacon , "James E.J. Bottomley" , Madhavan Srinivasan , Michael Ellerman , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jan Kara , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Kevin Brodsky , Muhammad Usama Anjum , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 3/5] mm/parisc: constify ptep_get() argument Message-ID: References: <20260724102017.141532-1-pfalcato@suse.de> <20260724102017.141532-4-pfalcato@suse.de> <0fd713a8-e4ab-4c07-b36e-79dd138b4a86@linux.dev> <253f7ac0-205b-42f1-9fb5-d19eceb581b6@linux.dev> <3e9dece8-4e86-4ce5-bd74-b3ec305f3003@gmx.de> <4606e13f-6827-45d0-b3b8-6bc26358f7ae@bell.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0CBB24000C X-Stat-Signature: 99fx4c9imbojaywa74jb7fsaq9858mwk X-Rspam-User: X-HE-Tag: 1785143707-560269 X-HE-Meta: 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 jV7WKWDG 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Jul 25, 2026 at 07:38:23PM +0200, Helge Deller wrote: > * John David Anglin : > > On 2026-07-25 12:27 p.m., Helge Deller wrote: > > > On 7/24/26 17:48, Usama Arif wrote: > > >> > > >> > > >> On 24/07/2026 16:32, Pedro Falcato wrote: > > >>> On Fri, Jul 24, 2026 at 04:03:44PM +0100, Usama Arif wrote: > > >>>> > > >>>> > > >>>> On 24/07/2026 15:14, Matthew Wilcox wrote: > > >>>>> On Fri, Jul 24, 2026 at 02:36:59PM +0100, Usama Arif wrote: > > >>>>>> > > >>>>>> > > >>>>>> On 24/07/2026 11:20, Pedro Falcato wrote: > > >>>>>>> ptep_get() does not need write access to the PTE. > > >>>>>>> > > >>>>>>> Signed-off-by: Pedro Falcato > > >>>>>>> --- > > >>>>>>>   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. > > >> > > >>> 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? > > Indeed, I missed to remove that. > > Usama, if you want you can add the patch below to your patch set, thus > simplifying your series? It's actually my series but thanks Helge I'll pick it up! > > Helge > > ------ > > From: Helge Deller > Date: Sat, 25 Jul 2026 19:19:55 +0200 > Subject: [PATCH] parisc: Drop own implementations for ptep_get() and > ptep_test_and_clear_young() > > Switch to the generic implementations, which are identical. > > Suggested-by: Usama Arif > Suggested-by: John David Anglin > Signed-off-by: Helge Deller > > diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h > index 467b8547ac8b..d92dee9fef3f 100644 > --- a/arch/parisc/include/asm/pgtable.h > +++ b/arch/parisc/include/asm/pgtable.h > @@ -432,25 +432,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) > return pte; > } > > -static inline pte_t ptep_get(pte_t *ptep) > -{ > - return READ_ONCE(*ptep); > -} > -#define ptep_get ptep_get > - > -static inline bool ptep_test_and_clear_young(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep) > -{ > - pte_t pte; > - > - pte = ptep_get(ptep); > - if (!pte_young(pte)) { > - return false; > - } > - set_pte_at(vma->vm_mm, addr, ptep, pte_mkold(pte)); > - return true; > -} > - > bool ptep_clear_flush_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep); > pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep); > > @@ -491,7 +472,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, > #define HAVE_ARCH_UNMAPPED_AREA > #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN > > -#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG > #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH > #define __HAVE_ARCH_PTEP_CLEAR_FLUSH > #define __HAVE_ARCH_PTEP_SET_WRPROTECT -- Pedro