From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F930CD98ED for ; Thu, 18 Jun 2026 07:45:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C65D6B008A; Thu, 18 Jun 2026 03:45:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 276BD6B008C; Thu, 18 Jun 2026 03:45:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 165E16B0092; Thu, 18 Jun 2026 03:45:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E81B36B008A for ; Thu, 18 Jun 2026 03:45:15 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 776981C2E1F for ; Thu, 18 Jun 2026 07:45:15 +0000 (UTC) X-FDA: 84892247790.16.4E8EF40 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) by imf04.hostedemail.com (Postfix) with ESMTP id 3E75940007 for ; Thu, 18 Jun 2026 07:45:12 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ozKxIvFA; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf04.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.178 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1781768713; 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; bh=gcdVk3SD/kQ6YP1sw609Ns7BDds+P1T+xzsWO6YjCAw=; b=RgG5oWLPFi9iaaeiIStLp+fPB4y562bNRb3uw7yzqdzjC9CAKVTJU3QSMUyAjMQr9ZE8kH BiqlEsTQzzVCUIbaGpxSd+qao4w310BdGTm18GzfiWvQNLgz/EUtEKQqhv2L5UcBEHX7Eq BzXZghrQuHJVW4Gw4z7zTMfuNQrbfHE= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ozKxIvFA; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf04.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.178 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1781768713; b=eD/u+NU8DQUHbL2ikI/NrHeLzQEvpKeuQk9awbdM/OOrBXt+7z8LaZX+GrBgkHBddCP89p CQY/j3LBkRYcBLa+KOD8q1AMfaCDDHuOkxlRbXLncYFj2eDnaxZYvc2UxiX7gbprD4VHjc 7grAf87OnJn3J7PHqD8FfLcjyRDihWM= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781768707; h=from:from: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; bh=gcdVk3SD/kQ6YP1sw609Ns7BDds+P1T+xzsWO6YjCAw=; b=ozKxIvFAUa6h8qFuqox1DC8GyPRZZujiOfjuuDrQw254LRyIDKt4OZLamnPy4oo5heYBWX S8iykcBIf8u8heJCx8X0llJ2A76HqkDqGhJZLr8N5wB1N3++onJa/MgXpoGpDXSP1/p3Yg h66F2AGBEaiRsFWs5KiOiHrtLEsGoPw= From: Lance Yang To: dev.jain@arm.com, david@kernel.org Cc: akpm@linux-foundation.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org, riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com, Lance Yang Subject: Re: [PATCH v4 02/12] mm/rmap: Add try_to_unmap_hugetlb_one Date: Thu, 18 Jun 2026 15:44:49 +0800 Message-Id: <20260618074449.24974-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3E75940007 X-Stat-Signature: de3g6zakrhc1f5gtnzd1k3gfsb4fkr4j X-Rspam-User: X-HE-Tag: 1781768712-868633 X-HE-Meta: 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 SLTwSkO+ X9wCs+v1OI4BVxo/7x3U59+SUlqH+YIIRDnPVYHU4trPGh7FuN09Ce3fK1+lwd/poG7UiYXI2SFII03/qlxEWzMh5nEAdj6HHGG5btBXhmdEj3JBswF6bXaQcIn1sv1xl5Uav+RbbRuLd3CsfooqffHfqf2myHvWFC0PEVczPQnNVp/8nRXjHxWwO6CR2JAtMIhdWsHu7c9fVwTcGHdzlBCHXAYewpq2m87B1WG7jv05v7PqAlJ9HkZus0nFpEG/r4E0u Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 09, 2026 at 04:16:47PM +0200, David Hildenbrand (Arm) wrote: [...] >> --- >> mm/rmap.c | 203 ++++++++++++++++++++++++++++++++---------------------- >> 1 file changed, 121 insertions(+), 82 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 430c91c8fe2ae..06ab1158d4cd1 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1978,6 +1978,121 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, >> FPB_RESPECT_WRITE | FPB_RESPECT_SOFT_DIRTY); >> } >> >> +static bool __try_to_unmap_hugetlb_one(struct folio *folio, >> + struct vm_area_struct *vma, struct page_vma_mapped_walk *pvmw, >> + struct mmu_notifier_range *range, enum ttu_flags flags) >> +{ >> + unsigned long hsz = huge_page_size(hstate_vma(vma)); > >Can be const. > >> + unsigned long address = pvmw->address; > >Can be const. But do we even need the temporary variable? > >> + struct mm_struct *mm = vma->vm_mm; >> + struct page *subpage; > >a) subpages do not exist. It's just a folio page. >b) subpages are irrelevant for hugetlb, just drop anything that deals with them. > >> + bool ret = true; >> + pte_t pteval; >> + > >Worth adding a comment here, why we don't need a loop. > >/* There is only a single mapping in a VMA. */ > >> + if (!page_vma_mapped_walk(pvmw)) >> + return true; >> + >> + pteval = ptep_get(pvmw->pte); > >Should we now properly use huge_ptep_get()? Right. IIUC, on s390, the hugetlb entry stored in the page table is not in the normal PTE layout. set_huge_pte_at() stores the arch huge-entry format there, and huge_ptep_get() is the helper that decodes it back into a normal pte_t. pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep) { return __rste_to_pte(pte_val(*ptep)); } >> + VM_WARN_ON(!pte_present(pteval)); >> + subpage = folio_page(folio, pte_pfn(pteval) - folio_pfn(folio)); > >No need for subpages. So plain ptep_get() can feed raw huge-entry bits into pte_pfn(), and the derived subpage can be wrong. Cheers, Lance [...]