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b=KaAXcaJ6BrbJXKn+9jc5GcmuMc74/jrdsBILvtUqu9fOwO7XhNg9Uj2oF3EnXkZZi rNPcDcm/YL82VDA3zwXDVLfBD+jmEdHGa9oHtn2Cb/UEDXtIZZM+fJfapADXdxVIRQ PassE6RB8NTNHvmQMzzoXwk4hRkakrEfk40GklflCunk2D93yXOuQblNDHvQg0vfXN TmBsl3jpo5LERjZXJrNgbhVQO4qFxDyFrEezRgHO3pRJgxTadsr//PBins24D0YHBv Da7NWE/mmSblYQPTu6sL098oDYOZ1RFFb5A3VmARVZlVeT5sC8fYdEdpZEEMsLjUru BX2gD+9BO/zxg== Message-ID: <4b36ddb9-c11a-4320-85d4-3e059e67384f@kernel.org> Date: Mon, 11 May 2026 09:37:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/9] mm/memory: Batch set uffd-wp markers during zapping To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, hughd@google.com, chrisl@kernel.org, kasong@tencent.com Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260506094504.2588857-1-dev.jain@arm.com> <20260506094504.2588857-5-dev.jain@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 75E8D8000A X-Stat-Signature: j7nwnqft8wt44qe847zztb66pspp7et5 X-Rspam-User: X-HE-Tag: 1778485046-68224 X-HE-Meta: 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 PzpnICee GSkx/AnoZyR1Z91OaNx+bjNTtNawWEqL2eW2nUGec7fdgGwLf1LhHTK0yQajX+EKwxVousp6x3MwojXgzJPi/t3KOEIyw166RhfxFiLLVzBT56Vrl7f11TwJ0L4tJFcR2D/AKO9pmcrrCGEVGtL2I++khTKLGvcj7axKEb8Mh2KXkJO2ARt4hh6WqstxyVa8iWwJeT+/7vwSw4I4L/E8Rzk0D3LFV7nkcwJ1na5QZpF3IDGCp1ovGHS5TQ4GOy5PqArL4DZeutDSQ8S2pW69QePWOrNkHl0o1yx2soqYhSBne7M5VeFi7ZezHwzI7xDXjn8Zj Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/6/26 11:44, Dev Jain wrote: > In preparation for the next patch, enable batch setting of uffd-wp ptes. > > The code paths passing nr > 1 to zap_install_uffd_wp_if_needed() produce > that nr through either folio_pte_batch or swap_pte_batch, guaranteeing that > all ptes are the same w.r.t belonging to the same type of VMA (anonymous > or non-anonymous, wp-armed or non-wp-armed), and all being marked with > uffd-wp or all being not marked. > > Note that we will have to use set_pte_at() in a loop instead of set_ptes() > since the latter cannot handle present->non-present conversion for > nr_pages > 1. > > Convert documentation of install_uffd_wp_ptes_if_needed to kerneldoc > format. You should mention why the uffd_supports_wp_marker()+vma_is_anonymous() calls in zap_install_uffd_wp_if_needed can be dropped. > > No functional change is intended. > > Signed-off-by: Dev Jain > --- > include/linux/mm_inline.h | 34 +++++++++++++++++++++------------- > mm/memory.c | 20 +------------------- > mm/rmap.c | 2 +- > 3 files changed, 23 insertions(+), 33 deletions(-) > > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h > index a171070e15f05..6f7ecede2fb45 100644 > --- a/include/linux/mm_inline.h > +++ b/include/linux/mm_inline.h > @@ -566,9 +566,17 @@ static inline pte_marker copy_pte_marker( > return dstm; > } > > -/* > - * If this pte is wr-protected by uffd-wp in any form, arm the special pte to > - * replace a none pte. NOTE! This should only be called when *pte is already > +/** > + * install_uffd_wp_ptes_if_needed - install uffd-wp marker on PTEs that map > + * consecutive pages of the same large folio. > + * @vma: The VMA the pages are mapped into. > + * @addr: Address the first page of this batch is mapped at. > + * @ptep: Page table pointer for the first entry of this batch. > + * @pteval: old value of the entry pointed to by ptep. > + * @nr_ptes: Number of entries to clear (batch size). > + * > + * If the ptes were wr-protected by uffd-wp in any form, arm special ptes to > + * replace none ptes. NOTE! This should only be called when *pte is already > * cleared so we will never accidentally replace something valuable. Meanwhile > * none pte also means we are not demoting the pte so tlb flushed is not needed. > * E.g., when pte cleared the caller should have taken care of the tlb flush. > @@ -576,11 +584,11 @@ static inline pte_marker copy_pte_marker( > * Must be called with pgtable lock held so that no thread will see the none > * pte, and if they see it, they'll fault and serialize at the pgtable lock. > * > - * Returns true if an uffd-wp pte was installed, false otherwise. > + * Returns true if uffd-wp ptes were installed, false otherwise. > */ > static inline bool > -pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, > - pte_t *pte, pte_t pteval) > +install_uffd_wp_ptes_if_needed(struct vm_area_struct *vma, unsigned long addr, > + pte_t *ptep, pte_t pteval, unsigned long nr_ptes) If we conditionally do something, what about while at it shorten it to: cont_install_uffd_wp_ptes() Also, less churn in this patch if you don't change pte->ptep (because if you do, you should then also do pteval->pte :) ) So I'd just leave that as is in this patch. > { > bool arm_uffd_pte = false; > > @@ -588,7 +596,7 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, > return false; > > /* The current status of the pte should be "cleared" before calling */ > - WARN_ON_ONCE(!pte_none(ptep_get(pte))); > + WARN_ON_ONCE(!pte_none(ptep_get(ptep))); > > /* > * NOTE: userfaultfd_wp_unpopulated() doesn't need this whole > @@ -610,13 +618,13 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, > if (unlikely(pte_swp_uffd_wp_any(pteval))) > arm_uffd_pte = true; > > - if (unlikely(arm_uffd_pte)) { > - set_pte_at(vma->vm_mm, addr, pte, > - make_pte_marker(PTE_MARKER_UFFD_WP)); > - return true; > - } > + if (likely(!arm_uffd_pte)) > + return false; > > - return false; > + for (int i = 0; i < nr_ptes; ++i, ++ptep, addr += PAGE_SIZE) > + set_pte_at(vma->vm_mm, addr, ptep, make_pte_marker(PTE_MARKER_UFFD_WP)); > + > + return true; > } I wonder whether this growing function is really appropriate to be in the header file? Can we just move that whole thing into mm/memory.c? It's called on every try_to_unmap_one() invocation, but I doubt we care about a function call here. > > static inline bool vma_has_recency(const struct vm_area_struct *vma) > diff --git a/mm/memory.c b/mm/memory.c > index 0c9d9c2cbf0e0..f14311c4d2001 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1610,29 +1610,11 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, > unsigned long addr, pte_t *pte, int nr, > struct zap_details *details, pte_t pteval) > { > - bool was_installed = false; > - > - if (!uffd_supports_wp_marker()) > - return false; > - > - /* Zap on anonymous always means dropping everything */ > - if (vma_is_anonymous(vma)) > - return false; > - > if (zap_drop_markers(details)) > return false; > > - for (;;) { > - /* the PFN in the PTE is irrelevant. */ > - if (pte_install_uffd_wp_if_needed(vma, addr, pte, pteval)) > - was_installed = true; > - if (--nr == 0) > - break; > - pte++; > - addr += PAGE_SIZE; > - } > + return install_uffd_wp_ptes_if_needed(vma, addr, pte, pteval, nr); > > - return was_installed; > } > > static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, > diff --git a/mm/rmap.c b/mm/rmap.c > index bd4e3639e26ed..b17dce752a1ea 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2266,7 +2266,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > * we may want to replace a none pte with a marker pte if > * it's file-backed, so we don't lose the tracking info. > */ > - pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); > + install_uffd_wp_ptes_if_needed(vma, address, pvmw.pte, pteval, 1); > > /* Update high watermark before we lower rss */ > update_hiwater_rss(mm); -- Cheers, David