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Thu, 10 Nov 2022 14:22:35 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) Subject: Re: [PATCH v8 1/2] hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing From: Nadav Amit In-Reply-To: Date: Thu, 10 Nov 2022 14:22:33 -0800 Cc: Linux-MM , kernel list , Naoya Horiguchi , David Hildenbrand , Axel Rasmussen , Mina Almasry , Peter Xu , Rik van Riel , Vlastimil Babka , Matthew Wilcox , Andrew Morton , Wei Chen , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <05FB2C99-9141-4F2A-8664-31CA5587B310@gmail.com> References: <20221108011910.350887-1-mike.kravetz@oracle.com> <20221108011910.350887-2-mike.kravetz@oracle.com> <9BB0EA0C-6E7C-462B-8374-5BFEC34E8415@gmail.com> To: Mike Kravetz X-Mailer: Apple Mail (2.3696.120.41.1.1) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668118957; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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spf=pass (imf09.hostedemail.com: domain of nadav.amit@gmail.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=nadav.amit@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1668118956-966029 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: On Nov 10, 2022, at 1:48 PM, Mike Kravetz = wrote: >>> void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long = start, >>> unsigned long end, struct page *ref_page, >>> zap_flags_t zap_flags) >>> { >>> + struct mmu_notifier_range range; >>> struct mmu_gather tlb; >>>=20 >>> + mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, = vma->vm_mm, >>> + start, end); >>> + adjust_range_if_pmd_sharing_possible(vma, &range.start, = &range.end); >>> tlb_gather_mmu(&tlb, vma->vm_mm); >>> + >>> __unmap_hugepage_range(&tlb, vma, start, end, ref_page, = zap_flags); >>=20 >> Is there a reason for not using range.start and range.end? >=20 > After calling adjust_range_if_pmd_sharing_possible, range.start - = range.end > could be much greater than the range we actually want to unmap. The = range > gets adjusted to account for pmd sharing if that is POSSIBLE. It does = not > know for sure if we will actually 'unshare a pmd'. >=20 > I suppose adjust_range_if_pmd_sharing_possible could be modified to = actually > check if unmapping will result in unsharing, but it does not do that = today. Thanks for the explanation. It=E2=80=99s probably me, but I am still not = sure that I understand the the different between __unmap_hugepage_range() using = (start, end) and __zap_page_range_single() using (address, range.end). Perhaps = it worth a comment in the code? But anyhow=E2=80=A6 shouldn=E2=80=99t unmap_hugepage_range() call mmu_notifier_invalidate_range_start()?