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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C5E0CF9C71 for ; Tue, 24 Sep 2024 08:25:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 00CEC6B008C; Tue, 24 Sep 2024 04:25:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EFD396B009A; Tue, 24 Sep 2024 04:25:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DC4E76B009C; Tue, 24 Sep 2024 04:25:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id BF0296B008C for ; Tue, 24 Sep 2024 04:25:48 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5F7B7A9CE7 for ; Tue, 24 Sep 2024 08:25:48 +0000 (UTC) X-FDA: 82598948376.11.D541F84 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) by imf17.hostedemail.com (Postfix) with ESMTP id 3B1B040005 for ; Tue, 24 Sep 2024 08:25:45 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Tjp0P3kf; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of muchun.song@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=muchun.song@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1727166250; a=rsa-sha256; cv=none; b=SLjDpAsEFuu+83MQsvexlq/3g0S3dhUNrfi5U+8U+Bb69PtTpBxpWJ4zcnszExAIJ5KW3k Vf4GIqJpH8tGZwd6CoTCa3HWFIkw1ARlWSp2R1cbciAVZBpKUM/r31tUqiq2yWPTgr3fDp HipXmoQnPmkithR3K5aeSvXHnZNjKwI= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Tjp0P3kf; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of muchun.song@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=muchun.song@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727166250; 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=1y5CwMb2yKa3w/NIt/ri0sQu3/1xDcimH4xSI7fLtgQ=; b=dm35PxSbHgr6sgQTKgBrm/alf6NET4V9vvy1hUAtQA6kakgWYmdtmLX3BGJNs5MYvRXtYn ifFR2jPxed7F8mTDgaogoTN3N1RS+0AcxiI1aG971JQvDJjskwRI3UgUKzwYBgCjntPaKb Wh97iEuHCSLDjQE2bh15ewdqRi2tA1A= Content-Type: text/plain; charset=utf-8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1727166344; 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=1y5CwMb2yKa3w/NIt/ri0sQu3/1xDcimH4xSI7fLtgQ=; b=Tjp0P3kfHa/lcIBU5PC1B0bQQCvLGfyq8015xxHclGgdFLLPxO/1pTOinxm0BDuczsBQUv m5ZY1EvglHhF0Inymte3gC1+yKjYpSfigpVX8d8pHJhpC3jeMXjhqqORPMtLQ/ZViMl3ti cU3EvV03qYBYxqNC+aDS+qZDaTycsVA= Content-Transfer-Encoding: quoted-printable X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v4 10/13] mm: page_vma_mapped_walk: map_pte() use pte_offset_map_rw_nolock() Date: Tue, 24 Sep 2024 16:25:06 +0800 Message-Id: References: Cc: david@redhat.com, hughd@google.com, willy@infradead.org, vbabka@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, vishal.moola@gmail.com, peterx@redhat.com, ryan.roberts@arm.com, christophe.leroy2@cs-soprasteria.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org In-Reply-To: To: Qi Zheng X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3B1B040005 X-Stat-Signature: 9hkoax6y8su6rkcr5c4awxs1zo1gj9cf X-Rspam-User: X-HE-Tag: 1727166345-823694 X-HE-Meta: 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 /MhLX8LB 4RvxP4JIw/BCpsqzqK5LZFQB6/hQvXZljanZyyJFxYu5bY3a8H1dohK87ZODXBg3ANmgHlvtgvjAbI/pLS/WE8HGG6U+dLb6Dmbcyrx2n7BR3gh+P2i6Ft/v5vAVEwiGyJiWOIw3B2E65ez7O+H4u1yGWlTAl3hdKAjjP74RpkepuoQgLcw8YPOYOAemnYrygcQrwGyPYZJVQrv2xfA8frTvvyG9hOIL5qGdcfEgULDq6wmATc1kAy9kHNkoSByheJmgH9GV9vvwxjY252x6aX1g6Hf7aGJfOVPMUY72jvgFr/ymsRSR4KQzHzibYwiEeAbNc 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: List-Subscribe: List-Unsubscribe: > On Sep 24, 2024, at 14:11, Qi Zheng wrote: >=20 > =EF=BB=BFIn the caller of map_pte(), we may modify the pvmw->pte after acq= uiring > the pvmw->ptl, so convert it to using pte_offset_map_rw_nolock(). At > this time, the pte_same() check is not performed after the pvmw->ptl held,= > so we should get pmdval and do pmd_same() check to ensure the stability of= > pvmw->pmd. >=20 > Signed-off-by: Qi Zheng > --- > mm/page_vma_mapped.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) >=20 > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index ae5cc42aa2087..6410f29b37c1b 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -13,9 +13,11 @@ static inline bool not_found(struct page_vma_mapped_wal= k *pvmw) > return false; > } >=20 > -static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)= > +static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp, > + spinlock_t **ptlp) > { > pte_t ptent; > + pmd_t pmdval; Why declare a new variable? Can=E2=80=99t we use *pmdvalp instead? >=20 > if (pvmw->flags & PVMW_SYNC) { > /* Use the stricter lookup */ > @@ -25,6 +27,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, s= pinlock_t **ptlp) > return !!pvmw->pte; > } >=20 > +again: > /* > * It is important to return the ptl corresponding to pte, > * in case *pvmw->pmd changes underneath us; so we need to > @@ -32,10 +35,11 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw,= spinlock_t **ptlp) > * proceeds to loop over next ptes, and finds a match later. > * Though, in most cases, page lock already protects this. > */ > - pvmw->pte =3D pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd, > - pvmw->address, ptlp); > + pvmw->pte =3D pte_offset_map_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd, > + pvmw->address, &pmdval, ptlp); > if (!pvmw->pte) > return false; > + *pmdvalp =3D pmdval; >=20 > ptent =3D ptep_get(pvmw->pte); >=20 > @@ -67,8 +71,13 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, s= pinlock_t **ptlp) > } else if (!pte_present(ptent)) { > return false; > } > + spin_lock(*ptlp); > + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pvmw->pmd)))) { > + pte_unmap_unlock(pvmw->pte, *ptlp); > + goto again; > + } > pvmw->ptl =3D *ptlp; > - spin_lock(pvmw->ptl); > + > return true; > } >=20 > @@ -278,7 +287,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *= pvmw) > step_forward(pvmw, PMD_SIZE); > continue; > } > - if (!map_pte(pvmw, &ptl)) { > + if (!map_pte(pvmw, &pmde, &ptl)) { > if (!pvmw->pte) > goto restart; > goto next_pte; > @@ -307,6 +316,12 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk= *pvmw) > if (!pvmw->ptl) { > pvmw->ptl =3D ptl; > spin_lock(pvmw->ptl); > + if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {= > + pte_unmap_unlock(pvmw->pte, pvmw->ptl); > + pvmw->ptl =3D NULL; > + pvmw->pte =3D NULL; > + goto restart; > + } > } > goto this_pte; > } while (pvmw->address < end); > -- > 2.20.1 >=20