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b=ArfQZAocn3bNOTGiysPVyOMe587mUPIZxvyXEE2Xhmcgglt7QoDFMi/M9Nnt6wohk NZz+f8NBf1if+1TK9UQz0R+uY005AH8rYmZJ1LVKkvfd3l1qkxuPW78axr7gpZDBFH unUm/P6Pn1tIvbeUobFDZLSk0Na8iGT96+hqTFrtI81ETKk24v5akjOiN5K/0AjD5x rI5UN5k8mVbb6/owKbo4OdpIsSyd/dpXw9HnhaVopbDBBZqI93jE3ObIL9nkmGkUsC AZbFx67KRYSxPSVl7oipYgkgroohTjeJP63MEAOZHaaK1Pgn601KvrBFay8s6kkfU2 Z28pnDyucyYaw== Message-ID: Date: Mon, 9 Feb 2026 10:54:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: rmap: skip batched unmapping for UFFD vmas To: Baolin Wang Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, baohua@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, harry.yoo@oracle.com, jannh@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, riel@surriel.com, rppt@kernel.org, ryan.roberts@arm.com, surenb@google.com, vbabka@suse.cz, will@kernel.org, willy@infradead.org References: <142919ac14d3cf70cba370808d85debe089df7b4.1766631066.git.baolin.wang@linux.alibaba.com> <20260116162652.176054-1-baolin.wang@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C175FA0002 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: wjjsbhy5xy39rdh1th3judztkuukifxz X-HE-Tag: 1770630879-529705 X-HE-Meta: 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 rISlq2EL kJ5TNjGJnRALyppD07ezFGDWp66/mV+ambwUV3dCXw8FI5K3OeHqk5lFfMhs+tbfTUYN/z9v1w7yMTVBJLnT9xoxIr6B/69O7YV+sqV6Zs9JmsD3wnEOlEf2mj/fCX4bcIKFL8MSIoQGTh2PXjs1HisjhZN2nV8vI/JxLj3QdfgRss0XXotZfzkFro9afJnH5NoTc6J1qoYx8EPa2tNqH6eElnUTjN8ojAHUnn7XC3BV+OEIEdGa3QkvQYR3pi/5NHXsxNyO6e9UzDDzWmYRZbyaYrg5+iXLJpzt/wNrtXPNZyQiZIcFWeLjEGTntMpcmgQbo99XmwZJWepcHrJY0et4g7rE4DNzmGD3B+MJE+mE3gKXUsMJo7td8d+muICZqeHbvtjJbKJyXcZo= 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 1/16/26 17:26, Baolin Wang wrote: > As Dev reported[1], it's not ready to support batched unmapping for uffd case. > Let's still fallback to per-page unmapping for the uffd case. > > [1] https://lore.kernel.org/linux-mm/20260116082721.275178-1-dev.jain@arm.com/ > Reported-by: Dev Jain > Suggested-by: Barry Song > Signed-off-by: Baolin Wang > --- > mm/rmap.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/rmap.c b/mm/rmap.c > index f13480cb9f2e..172643092dcf 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1953,6 +1953,9 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, > if (pte_unused(pte)) > return 1; > > + if (userfaultfd_wp(vma)) > + return 1; > + Interesting. I was just wondering why we didn't run into that with lazyfree folios. Staring at pte_install_uffd_wp_if_needed(), we never set the marker for anonymous VMAs. So, yeah, if one sets lazyfree on a uffd-wp PTE, the uffd-wp bit will just get zapped alongside. Just like MADV_DONTNEED. I'm fine with that temporary fix. But I guess the non-hacky way to handle this would be: From 53d016d6e6f624425dbdbc2fb1dec7c91fbef15c Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Mon, 9 Feb 2026 10:52:59 +0100 Subject: [PATCH] tmp Signed-off-by: David Hildenbrand (Arm) --- include/linux/mm_inline.h | 15 ++++++--------- mm/memory.c | 21 +-------------------- mm/rmap.c | 2 +- 3 files changed, 8 insertions(+), 30 deletions(-) diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index fa2d6ba811b5..8a9a2c5f5ee3 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -566,9 +566,8 @@ static inline pte_marker copy_pte_marker( * * Returns true if an uffd-wp pte was 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) +static inline bool install_uffd_wp_ptes_if_needed(struct vm_area_struct *vma, + unsigned long addr, pte_t *pte, unsigned int nr, pte_t pteval) { bool arm_uffd_pte = false; @@ -598,13 +597,11 @@ 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; + set_ptes(vma->vm_mm, addr, pte, make_pte_marker(PTE_MARKER_UFFD_WP), nr); + return true; } static inline bool vma_has_recency(const struct vm_area_struct *vma) diff --git a/mm/memory.c b/mm/memory.c index da360a6eb8a4..0a87d02a9a69 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1592,29 +1592,10 @@ 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 was_installed; + return install_uffd_wp_ptes_if_needed(vma, addr, pte, nr, pteval); } static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, diff --git a/mm/rmap.c b/mm/rmap.c index 7b9879ef442d..f71aacf35925 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2061,7 +2061,7 @@ 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, nr_pages, pteval); /* Update high watermark before we lower rss */ update_hiwater_rss(mm); -- 2.43.0 Does somebody have time to look into that? We should also adjust the doc of pte_install_uffd_wp_if_needed() and turn it into some proper kerneldoc. -- Cheers, David