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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 139E0ECAAA2 for ; Mon, 29 Aug 2022 02:44:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229662AbiH2Coi (ORCPT ); Sun, 28 Aug 2022 22:44:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229630AbiH2Coe (ORCPT ); Sun, 28 Aug 2022 22:44:34 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6ECB73C8F5 for ; Sun, 28 Aug 2022 19:44:32 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4MGF6t09glz1N7ck; Mon, 29 Aug 2022 10:40:54 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 29 Aug 2022 10:44:29 +0800 Subject: Re: [PATCH 7/8] hugetlb: create hugetlb_unmap_file_folio to unmap single file folio To: Mike Kravetz CC: Muchun Song , David Hildenbrand , Michal Hocko , Peter Xu , Naoya Horiguchi , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , James Houghton , Mina Almasry , Pasha Tatashin , Axel Rasmussen , Ray Fucillo , Andrew Morton , , References: <20220824175757.20590-1-mike.kravetz@oracle.com> <20220824175757.20590-8-mike.kravetz@oracle.com> From: Miaohe Lin Message-ID: <0e31f9da-5953-2f44-1a59-888e3313e919@huawei.com> Date: Mon, 29 Aug 2022 10:44:28 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220824175757.20590-8-mike.kravetz@oracle.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/8/25 1:57, Mike Kravetz wrote: > Create the new routine hugetlb_unmap_file_folio that will unmap a single > file folio. This is refactored code from hugetlb_vmdelete_list. It is > modified to do locking within the routine itself and check whether the > page is mapped within a specific vma before unmapping. > > This refactoring will be put to use and expanded upon in a subsequent > patch adding vma specific locking. > > Signed-off-by: Mike Kravetz > --- > fs/hugetlbfs/inode.c | 123 +++++++++++++++++++++++++++++++++---------- > 1 file changed, 94 insertions(+), 29 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index e83fd31671b3..b93d131b0cb5 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -371,6 +371,94 @@ static void hugetlb_delete_from_page_cache(struct page *page) > delete_from_page_cache(page); > } > > +/* > + * Called with i_mmap_rwsem held for inode based vma maps. This makes > + * sure vma (and vm_mm) will not go away. We also hold the hugetlb fault > + * mutex for the page in the mapping. So, we can not race with page being > + * faulted into the vma. > + */ > +static bool hugetlb_vma_maps_page(struct vm_area_struct *vma, > + unsigned long addr, struct page *page) > +{ > + pte_t *ptep, pte; > + > + ptep = huge_pte_offset(vma->vm_mm, addr, > + huge_page_size(hstate_vma(vma))); > + > + if (!ptep) > + return false; > + > + pte = huge_ptep_get(ptep); > + if (huge_pte_none(pte) || !pte_present(pte)) > + return false; > + > + if (pte_page(pte) == page) > + return true; I'm thinking whether pte entry could change after we check it since huge_pte_lock is not held here. But I think holding i_mmap_rwsem in writelock mode should give us such a guarantee, e.g. migration entry is changed back to huge pte entry while holding i_mmap_rwsem in readlock mode. Or am I miss something? > + > + return false; > +} > + > +/* > + * Can vma_offset_start/vma_offset_end overflow on 32-bit arches? > + * No, because the interval tree returns us only those vmas > + * which overlap the truncated area starting at pgoff, > + * and no vma on a 32-bit arch can span beyond the 4GB. > + */ > +static unsigned long vma_offset_start(struct vm_area_struct *vma, pgoff_t start) > +{ > + if (vma->vm_pgoff < start) > + return (start - vma->vm_pgoff) << PAGE_SHIFT; > + else > + return 0; > +} > + > +static unsigned long vma_offset_end(struct vm_area_struct *vma, pgoff_t end) > +{ > + unsigned long t_end; > + > + if (!end) > + return vma->vm_end; > + > + t_end = ((end - vma->vm_pgoff) << PAGE_SHIFT) + vma->vm_start; > + if (t_end > vma->vm_end) > + t_end = vma->vm_end; > + return t_end; > +} > + > +/* > + * Called with hugetlb fault mutex held. Therefore, no more mappings to > + * this folio can be created while executing the routine. > + */ > +static void hugetlb_unmap_file_folio(struct hstate *h, > + struct address_space *mapping, > + struct folio *folio, pgoff_t index) > +{ > + struct rb_root_cached *root = &mapping->i_mmap; > + struct page *page = &folio->page; > + struct vm_area_struct *vma; > + unsigned long v_start; > + unsigned long v_end; > + pgoff_t start, end; > + > + start = index * pages_per_huge_page(h); > + end = ((index + 1) * pages_per_huge_page(h)); It seems the outer parentheses is unneeded? Reviewed-by: Miaohe Lin Thanks, Miaohe Lin