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b=b5iDMqJCBC1aU7JpWvScNn24L8blw4eqpRra2otsN93uWoz3OMEDrrCZ5GJ6LBTiU MXzOzb/PTKR+IOEma0tAqB2pCRgOY2l35r1PThRcu1HiWKgtVDbgF2tytBMp7uv53h 8DD1bT7I0ywHgRogmT+wJho1Dbak1+glBsKRkiE5/iL/+4yyfPRt2gUMXmNVjWcJTS 6o5+blWnHlaC7Zn2+xy3ZpnitfmIykuGxyWqsVcZo+PdfV1KdUfm7bFlQ6dF38A2O/ U6ifEOQqSObypThyn8dl7/RVTRXRv5z1tVO+7QcQJzNIGJm2Tyv7wU8Nbd0vld+jMx sxofWNdQFmXyQ== Message-ID: Date: Mon, 11 May 2026 09:41:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/9] mm/rmap: batch unmap folios belonging to uffd-wp VMAs 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> <20260506094504.2588857-6-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-Stat-Signature: 4nx3yhuqh7ecfx96meiy4jr94oj7hksm X-Rspamd-Queue-Id: B39F28000A X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1778485273-109893 X-HE-Meta: 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 b76LRwFM oB2HSoLCek+pcH7neSWSGg7Imotarwn0Y3dge1m2l3Q3zE2Ps99gVrJ48Xd/9HiEB3oA9IzFFxFkbOJRc2mk4vEUofUcuCDCKtHbLcmclh73oqzkBe5cjzocCEH5MHd5Z118toymHmq726Me6X3jnAVKTEOx27ilP6OBylDdaki1zl8tiWgiKtrGFR/hLJniAQDmWs8DRCE4DaNUGg7P9l59/9ytuKujQbjeEb/+prMVGH+NnNwy/dxvk4zi8cUYcUEa6iG4gJbVPTCH+vHppjxaTP4R1vPZwPm9O2N4YHkPNOMi3V+PItDsfPZIsF47eMTfeJBHLJKYQX4MW7/Xg4DC5WA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/6/26 11:45, Dev Jain wrote: > Commit a67fe41e214f ("mm: rmap: support batched unmapping for file large folios") > extended batched unmapping for file folios. That also required making > install_uffd_wp_ptes_if_needed() support batching, but that was left > out for the time being, and correctness was maintained by stopping > batching in case the VMA the folio belongs to is marked uffd-wp. > > Now that we have a batched version called install_uffd_wp_ptes_if_needed, > simply call that. folio_unmap_pte_batch() ensures that the original state > of the ptes is either all uffd or all non-uffd, so we maintain > correctness. > > If uffd-wp bit is there, we have the following transitions of ptes > after unmapping: > > 1) anon folio: present -> uffd-wp swap > 2) file folio: present -> uffd-wp marker > > We must ensure that these ptes are not reprocessed by the while loop - > if the batch length is less than the number of pages in the folio, then > we must skip over this batch. > > The page_vma_mapped_walk API ensures this - check_pte() will return true > only if any of [pvmw->pfn, pvmw->pfn + nr_pages) is mapped by the pte. > There is no pfn underlying either a uffd-wp swap pte or a uffd-wp marker > pte, so check_pte returns false and we keep skipping until we hit a > present entry, which is where we want to batch from next. Right. Or a non-present ZONE_DEVICE entry. Your patch shouldn't change anything about that. > > Signed-off-by: Dev Jain > --- > mm/rmap.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index b17dce752a1ea..25813e3605991 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1965,9 +1965,6 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, > if (pte_unused(pte)) > return 1; > > - if (userfaultfd_wp(vma)) > - return 1; > - > /* > * If unmap fails, we need to restore the ptes. To avoid accidentally > * upgrading write permissions for ptes that were not originally > @@ -2266,7 +2263,7 @@ 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. > */ > - install_uffd_wp_ptes_if_needed(vma, address, pvmw.pte, pteval, 1); > + install_uffd_wp_ptes_if_needed(vma, address, pvmw.pte, pteval, nr_pages); > > /* Update high watermark before we lower rss */ > update_hiwater_rss(mm); Yes, that should do the trick. folio_pte_batch_flags() will still respect the uffd-wp bit. Acked-by: David Hildenbrand (Arm) -- Cheers, David