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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: ant94rcb7h9ibqjdhmi4wrwm9wkxkeju X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2FA06180004 X-Rspam-User: X-HE-Tag: 1745902786-807132 X-HE-Meta: U2FsdGVkX19hRT+AEVzMsBITbc+ZK3nirZ06C8eelj1KC7yP/aibLD40j8sSgP3/V+ON5atU4pbQLtz70J9tLu9plsNZE8F1eC1vG5Kn6j6nUOAPsnqSsCmH2xiAi6j15NBwBIgMD1yjx35Gh82rp3IuswA5NQHLyvr7ynJAGo7F8HRPDRm9F+2a7riNUAKOso8x9a08IeF9Qq6E6FwzNZrsjvmwkVTxE46evCejhQYDyjsJJnXfQdL3hNZr2LfkjNCAcA6g1oK71IOeO+g4PdlFxu56g2kF3+4iX8FobBFNO2lCrHgcQ0o1p1iQANuSvTGgCZ29t6W7yNPNHF8HllJpvgxlez3whjLn5fZ7oHdmN7/w4cZZX4uahurZmUuqphTfCyhudUHlcxR31KkJrd2cZ2thhxJ3QFe+4HYF6PixQG/sFZVphhOUSm+He/Bl7zesgsR/aHyTL8a/V1bEsWliEGO19zQP8ZvDv9xi+1E8V55D9S3Rj8CRcDUde6F5C1HZ2k4DAIx8tYDe1UJ8E6rlMJfs5MHigw8Mu738IgiBDXUd8ngSHtZvI+tp2uYGVO+2eBkD5Wy8oMbxdp2Z5TLJOaw5HIN69ezfxagWaxZrQNxuYlQGCcnJGVcgE00nljTkY6Y7SqHAOEhYH9U4YIOrJftu4BzOVhC++XP+MsuNoFKnC0zjOIARoxWhHoOOnRRTNJc8ImFMD+oh7Q3mIS0nIUmaToENEIRrdktnMGoMw+S6TnMgUywX7nSkzT/rz3iUwhHhjzoNGxbZWmyTRAmlMSaIWF2Pt2DwmrcORYllBPZsGV+rvSvncWngjD/g9AlXNwwOLOPTKLTGOT8vCtz/NnHoFNMO0CxNdB9rS1AH3LcCApaXboPX+nb1JQSoDgBbyygp4xjEGl81JfHAJ+fupMscw9Ro+l1ecxEPS/0b5CaiR0DcIt++jcydq1NjwEWamZsFDV8hYag8ZbN FpSwMHJ6 9+zJO/ZptcDND0mdNVnzT32kMfSdYOmzrrdXJkxqKFfQHanmrP3fguQtiYhp2Y7vBDeQE/0H1Qaottg0KOdD3r+S2CfNP0adjYU6JVqxaWDcc/wFwepFKpTIy4bUODo83m2ZBB4qJVK7I+D46RS0ry7VTOcdy1RWn/f7PbCfBcpelRPXGjvuPjvJtxmtEHxuVGfejKIcnes7zhVfrl3TwK5rktl/dzlGh+ApQtwmLazKMOfzH2I2uSJ+Gb+nQtXgbve4LlEe94++DdFmb16I7f5nEfQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 28/04/25 6:53 pm, Lance Yang wrote: > > > On 2025/4/28 20:59, Dev Jain wrote: >> >> >> On 28/04/25 6:20 pm, Lance Yang wrote: >>> Hey Dev, >>> >>> On 2025/4/28 20:04, Dev Jain wrote: >>>> In preparation for patch 7, we need to properly batch around >>>> can_change_pte_writable(). We batch around pte_needs_soft_dirty_wp() by >>>> the corresponding fpb flag, we batch around the page-anon exclusive >>>> check >>>> using folio_maybe_mapped_shared(); modify_prot_start_ptes() collects >>>> the >>>> dirty and access bits across the batch, therefore batching across >>>> pte_dirty(): this is correct since the dirty bit on the PTE really >>>> is just an indication that the folio got written to, so even if >>>> the PTE is not actually dirty (but one of the PTEs in the batch is), >>>> the wp-fault optimization can be made. >>>> >>>> Signed-off-by: Dev Jain >>>> --- >>>>   include/linux/mm.h | 4 ++-- >>>>   mm/gup.c           | 2 +- >>>>   mm/huge_memory.c   | 4 ++-- >>>>   mm/memory.c        | 6 +++--- >>>>   mm/mprotect.c      | 9 ++++++--- >>>>   5 files changed, 14 insertions(+), 11 deletions(-) >>>> >>>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>>> index 5eb0d77c4438..ffa02e15863f 100644 >>>> --- a/include/linux/mm.h >>>> +++ b/include/linux/mm.h >>>> @@ -2710,8 +2710,8 @@ int get_cmdline(struct task_struct *task, char >>>> *buffer, int buflen); >>>>   #define  MM_CP_UFFD_WP_ALL                 (MM_CP_UFFD_WP | \ >>>>                           MM_CP_UFFD_WP_RESOLVE) >>>> -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> -                 pte_t pte); >>>> +bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> +                 pte_t pte, struct folio *folio, unsigned int nr); >>>>   extern long change_protection(struct mmu_gather *tlb, >>>>                     struct vm_area_struct *vma, unsigned long start, >>>>                     unsigned long end, unsigned long cp_flags); >>>> diff --git a/mm/gup.c b/mm/gup.c >>>> index 84461d384ae2..6a605fc5f2cb 100644 >>>> --- a/mm/gup.c >>>> +++ b/mm/gup.c >>>> @@ -614,7 +614,7 @@ static inline bool >>>> can_follow_write_common(struct page *page, >>>>           return false; >>>>       /* >>>> -     * See can_change_pte_writable(): we broke COW and could map >>>> the page >>>> +     * See can_change_ptes_writable(): we broke COW and could map >>>> the page >>>>        * writable if we have an exclusive anonymous page ... >>>>        */ >>>>       return page && PageAnon(page) && PageAnonExclusive(page); >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index 28c87e0e036f..e5496c0d9e7e 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -2032,12 +2032,12 @@ static inline bool >>>> can_change_pmd_writable(struct vm_area_struct *vma, >>>>           return false; >>>>       if (!(vma->vm_flags & VM_SHARED)) { >>>> -        /* See can_change_pte_writable(). */ >>>> +        /* See can_change_ptes_writable(). */ >>>>           page = vm_normal_page_pmd(vma, addr, pmd); >>>>           return page && PageAnon(page) && PageAnonExclusive(page); >>>>       } >>>> -    /* See can_change_pte_writable(). */ >>>> +    /* See can_change_ptes_writable(). */ >>>>       return pmd_dirty(pmd); >>>>   } >>>> diff --git a/mm/memory.c b/mm/memory.c >>>> index b9e8443aaa86..b1fda3de8d27 100644 >>>> --- a/mm/memory.c >>>> +++ b/mm/memory.c >>>> @@ -750,7 +750,7 @@ static void restore_exclusive_pte(struct >>>> vm_area_struct *vma, >>>>           pte = pte_mkuffd_wp(pte); >>>>       if ((vma->vm_flags & VM_WRITE) && >>>> -        can_change_pte_writable(vma, address, pte)) { >>>> +        can_change_ptes_writable(vma, address, pte, NULL, 1)) { >>>>           if (folio_test_dirty(folio)) >>>>               pte = pte_mkdirty(pte); >>>>           pte = pte_mkwrite(pte, vma); >>>> @@ -5767,7 +5767,7 @@ static void numa_rebuild_large_mapping(struct >>>> vm_fault *vmf, struct vm_area_stru >>>>               ptent = pte_modify(ptent, vma->vm_page_prot); >>>>               writable = pte_write(ptent); >>>>               if (!writable && pte_write_upgrade && >>>> -                can_change_pte_writable(vma, addr, ptent)) >>>> +                can_change_ptes_writable(vma, addr, ptent, NULL, 1)) >>>>                   writable = true; >>>>           } >>>> @@ -5808,7 +5808,7 @@ static vm_fault_t do_numa_page(struct vm_fault >>>> *vmf) >>>>        */ >>>>       writable = pte_write(pte); >>>>       if (!writable && pte_write_upgrade && >>>> -        can_change_pte_writable(vma, vmf->address, pte)) >>>> +        can_change_ptes_writable(vma, vmf->address, pte, NULL, 1)) >>>>           writable = true; >>>>       folio = vm_normal_folio(vma, vmf->address, pte); >>>> diff --git a/mm/mprotect.c b/mm/mprotect.c >>>> index 33eabc995584..362fd7e5457d 100644 >>>> --- a/mm/mprotect.c >>>> +++ b/mm/mprotect.c >>>> @@ -40,8 +40,8 @@ >>>>   #include "internal.h" >>>> -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> -                 pte_t pte) >>>> +bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> +                  pte_t pte, struct folio *folio, unsigned int nr) >>>>   { >>>>       struct page *page; >>>> @@ -67,6 +67,9 @@ bool can_change_pte_writable(struct vm_area_struct >>>> *vma, unsigned long addr, >>>>            * write-fault handler similarly would map them writable >>>> without >>>>            * any additional checks while holding the PT lock. >>>>            */ >>>> +        if (unlikely(nr != 1)) >>>> +            return !folio_maybe_mapped_shared(folio); >>>> + >>>>           page = vm_normal_page(vma, addr, pte); >>>>           return page && PageAnon(page) && PageAnonExclusive(page); >>>>       } >>> >>> IIUC, As mentioned in the comment above, we should do the same >>> anonymous check >>> to large folios. And folio_maybe_mapped_shared() already handles both >>> order-0 >>> and large folios nicely, so we could simplify the logic as follows: >> >> Thanks. Although we will have to call vm_normal_folio() in case of ! >> folio, since we may not have the folio already for nr == 1 case. > > Ah, I see. Should we still check folio_test_anon() when nr != 1? According to the comment, "We can only special-case on exclusive anonymous pages", I would say yes. > > Thanks, > Lance > >> >>> >>> diff --git a/mm/mprotect.c b/mm/mprotect.c >>> index 1605e89349d2..df56a30bb241 100644 >>> --- a/mm/mprotect.c >>> +++ b/mm/mprotect.c >>> @@ -43,8 +43,6 @@ >>>   bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned >>> long addr, >>>                                pte_t pte, struct folio *folio, >>> unsigned int nr) >>>   { >>> -       struct page *page; >>> - >>>          if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) >>>                  return false; >>> >>> @@ -67,11 +65,7 @@ bool can_change_ptes_writable(struct >>> vm_area_struct *vma, unsigned long addr, >>>                   * write-fault handler similarly would map them >>> writable without >>>                   * any additional checks while holding the PT lock. >>>                   */ >>> -               if (unlikely(nr != 1)) >>> -                       return !folio_maybe_mapped_shared(folio); >>> - >>> -               page = vm_normal_page(vma, addr, pte); >>> -               return page && PageAnon(page) && >>> PageAnonExclusive(page); >>> +               return folio_test_anon(folio) && ! >>> folio_maybe_mapped_shared(folio); >>>          } >>> >>>          VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)); >>> -- >>> >>> Thanks, >>> Lance >>> >>>> @@ -222,7 +225,7 @@ static long change_pte_range(struct mmu_gather >>>> *tlb, >>>>                */ >>>>               if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && >>>>                   !pte_write(ptent) && >>>> -                can_change_pte_writable(vma, addr, ptent)) >>>> +                can_change_ptes_writable(vma, addr, ptent, folio, 1)) >>>>                   ptent = pte_mkwrite(ptent, vma); >>>>               ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent); >>> >>> >> > >