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 13FBDC4321E for ; Wed, 30 Nov 2022 16:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229811AbiK3QTp (ORCPT ); Wed, 30 Nov 2022 11:19:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbiK3QTm (ORCPT ); Wed, 30 Nov 2022 11:19:42 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D67754D5EB for ; Wed, 30 Nov 2022 08:18:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669825130; 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=cnZGBkwWgbFX167qaVZmI9S2d5cNmBBPcO+crFwoMks=; b=UihkukJMdy7/ktcRu3ozOWLL0uQGi4V5qqBRX8IWwBnLi5fsvGNFiJFlekHKcU8L1LgGtY oLDIQAIZUXNwiFQUek8ZsgcxgetZZfp2AQYVcGfUYEl6VRW9q3P7XsL65asOhjwb4IIGJy zRtj0Y2a90hOwmeKYcBrEiT+m2UXOJ0= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-616-k5qbtME1Pd2dtHP8scxEPQ-1; Wed, 30 Nov 2022 11:18:48 -0500 X-MC-Unique: k5qbtME1Pd2dtHP8scxEPQ-1 Received: by mail-wm1-f72.google.com with SMTP id v188-20020a1cacc5000000b003cf76c4ae66so1171686wme.7 for ; Wed, 30 Nov 2022 08:18:47 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:subject:organization:from :references:cc:to:content-language:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=cnZGBkwWgbFX167qaVZmI9S2d5cNmBBPcO+crFwoMks=; b=C2T+bbVAqt2U6+DQRRrxE6udP+bUH5Q+7UnbMUGlarHQjf8hRKJ3e68NTn29jhMCLa FJIxjuAeOLE+vyD4uPsvJGj1L2Byy93JbSAlJk6thgpwfBQE7fO1coI0jNwoMkhoZ9zp fjlMzfPY773PF/fjtfZxA8kFivXCkmhRDoKBbHhSc6YL2dCqZ97G0RwiB71mHKwkh7Fx nYWQm1MsVyTKzYipdsnfWew/q32qS0ZtwQmy7jUv64RZMkl1FSFwB/FxzUMrRYyHjM7Y jHAN9r+0+kKm1B8JP3OjE7tdGjGRiB9jd8jq1oDBswbNLjlP5Y93cGoHr/UDA0Lqr73Q cC/g== X-Gm-Message-State: ANoB5pmzdz0GSab8T2Oy5jRHhx4wRRqQS1LtJQAHwlTMX0cyHBMws1B6 rD3dJiotPc1cqmg6h9JLu/5rHyRLuHQDPLw57B+r8GkbV1Fk1vMFELtt5mRmJugHGau8Wla0v8B NM/m2FacH8UnA5KCdFSm1Vfkv X-Received: by 2002:adf:a357:0:b0:242:2669:be96 with SMTP id d23-20020adfa357000000b002422669be96mr4527490wrb.713.1669825126875; Wed, 30 Nov 2022 08:18:46 -0800 (PST) X-Google-Smtp-Source: AA0mqf7A6sXPnq+UQVA7DWGCrB2WPLau85zrzR/9C04F6J581F2ohdEXx496Fwz9ibJTCvV4eTXMXA== X-Received: by 2002:adf:a357:0:b0:242:2669:be96 with SMTP id d23-20020adfa357000000b002422669be96mr4527469wrb.713.1669825126564; Wed, 30 Nov 2022 08:18:46 -0800 (PST) Received: from ?IPV6:2003:cb:c703:7600:a8ea:29ce:7ee3:dd41? (p200300cbc7037600a8ea29ce7ee3dd41.dip0.t-ipconnect.de. [2003:cb:c703:7600:a8ea:29ce:7ee3:dd41]) by smtp.gmail.com with ESMTPSA id m21-20020a05600c4f5500b003b4fe03c881sm6809659wmq.48.2022.11.30.08.18.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Nov 2022 08:18:46 -0800 (PST) Message-ID: <65a3a912-3534-6718-2c55-e0d4b5246f1e@redhat.com> Date: Wed, 30 Nov 2022 17:18:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Content-Language: en-US To: Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: James Houghton , Jann Horn , Andrew Morton , Andrea Arcangeli , Rik van Riel , Nadav Amit , Miaohe Lin , Muchun Song , Mike Kravetz References: <20221129193526.3588187-1-peterx@redhat.com> <20221129193526.3588187-10-peterx@redhat.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH 09/10] mm/hugetlb: Make page_vma_mapped_walk() safe to pmd unshare In-Reply-To: <20221129193526.3588187-10-peterx@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29.11.22 20:35, Peter Xu wrote: > Since page_vma_mapped_walk() walks the pgtable, it needs the vma lock > to make sure the pgtable page will not be freed concurrently. > > Signed-off-by: Peter Xu > --- > include/linux/rmap.h | 4 ++++ > mm/page_vma_mapped.c | 5 ++++- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index bd3504d11b15..a50d18bb86aa 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -13,6 +13,7 @@ > #include > #include > #include > +#include > > /* > * The anon_vma heads a list of private "related" vmas, to scan if > @@ -408,6 +409,9 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) > pte_unmap(pvmw->pte); > if (pvmw->ptl) > spin_unlock(pvmw->ptl); > + /* This needs to be after unlock of the spinlock */ > + if (is_vm_hugetlb_page(pvmw->vma)) > + hugetlb_vma_unlock_read(pvmw->vma); > } > > bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw); > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index 93e13fc17d3c..f94ec78b54ff 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -169,10 +169,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) > if (pvmw->pte) > return not_found(pvmw); > > + hugetlb_vma_lock_read(vma); > /* when pud is not present, pte will be NULL */ > pvmw->pte = huge_pte_offset(mm, pvmw->address, size); > - if (!pvmw->pte) > + if (!pvmw->pte) { > + hugetlb_vma_unlock_read(vma); > return false; > + } > > pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte); > if (!check_pte(pvmw)) Looking at code like mm/damon/paddr.c:__damon_pa_mkold() and reading the doc of page_vma_mapped_walk(), this might be broken. Can't we get page_vma_mapped_walk() called multiple times? Wouldn't we have to remember that we already took the lock to not lock twice, and to see if we really have to unlock in page_vma_mapped_walk_done() ? -- Thanks, David / dhildenb