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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5A772CD5BA8 for ; Thu, 5 Sep 2024 10:31:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=nRCI2DeauznMxWvt70Qz7zNit5+Q7VEXvujH0nECZ00=; b=kdetlU1uW7BE+BUgJlUCo6um8V +7pwHgBrgg+mXFTQmuIcEW0JPaAe4e3fXv//XUEyyOmJeQo3rNKOWpBgd0sucP5jeT8n1QqZbJx0/ flo8JUqlDy0vYM6tKc4/yVHGUAkzHiYR591k5u6vxhFjtVtioHqtaSS9uSx8f65TsyCBW7yAsAP3N ypqko1oGwq0YkSswM96RrGQa+qsndOWGTKGP0AOEx/A68a1gjL7t6PH2nxeUH1xqGu26aYNY0d+zu nYkvjV5jtSOeuHm4HyiqMbcYCYjntLgSwUrp1+z7N+1NJqpjD3sl4MBmZSXBAwTM2tRaGnst0mk+/ xAG896Xg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sm9lU-00000007yBL-2d9y; Thu, 05 Sep 2024 10:31:00 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sm8ku-00000007l06-1MKr for linux-arm-kernel@bombadil.infradead.org; Thu, 05 Sep 2024 09:26:20 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID: Sender:Reply-To:Content-ID:Content-Description; bh=nRCI2DeauznMxWvt70Qz7zNit5+Q7VEXvujH0nECZ00=; b=nd5MkPCdAuO7Psa8RGsq4+8zaA FelL6AJbzG7eWNWSDIpHH9kQW+xa0S5RAE7zwW7MUo3kjE2RY/nXnVDElUsbwtHdDObl7Sq22nYQp JZHI++2zsp8Ae45JCtmvYkKaZxyCk7yKOVr7jzy+ElBLshVv6doc0UYeOnmkozOnpsVLUkYM1rrJt 0olWFgGoddX8WlOkscmXB/JiDcWiH4IWN2tACqLmDHZb0Czp1BPYZli/1tAELY1HAqZj1ZUNtvVoc +mYWNKZIMFS4VtlTBzLHjXvBwcSaBbC6evVo9TMLMiiuC6PMx6krfw9CESoW+NFSO1h0L/BGGYbOl YthPVKXQ==; Received: from out-184.mta0.migadu.com ([2001:41d0:1004:224b::b8]) by desiato.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1sm8kr-00000000S6m-1aDe for linux-arm-kernel@lists.infradead.org; Thu, 05 Sep 2024 09:26:19 +0000 Message-ID: <1b03a7de-1278-4e36-8068-885dd1c29742@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1725528373; 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=nRCI2DeauznMxWvt70Qz7zNit5+Q7VEXvujH0nECZ00=; b=c5FUB6sPdqxWX5L5xjOt1q9V2UQS4qiyKBlN6A7HKzXewrgQGG88vVjQ6bDaNQQo3schKq YNRZQuDJhFK8TX1j8wy49QWAZ03RWVSuz2vaYOxZxfj/ZHKvWeloeHACU3d7xsCnCQyqgf ADgGTiaDgUYLEr5AY+sqdyxdpx8HdTQ= Date: Thu, 5 Sep 2024 17:25:44 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v3 09/14] mm: mremap: move_ptes() use pte_offset_map_rw_nolock() To: Qi Zheng Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, 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 References: <20240904084022.32728-1-zhengqi.arch@bytedance.com> <20240904084022.32728-10-zhengqi.arch@bytedance.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20240904084022.32728-10-zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240905_102617_549417_3B64B24E X-CRM114-Status: GOOD ( 18.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2024/9/4 16:40, Qi Zheng wrote: > In move_ptes(), we may modify the new_pte after acquiring the new_ptl, so > convert it to using pte_offset_map_rw_nolock(). Since we may free the PTE > page in retract_page_tables() without holding the read lock of mmap_lock, > so we still need to do a pmd_same() check after holding the PTL. retract_page_tables() and move_ptes() are synchronized with i_mmap_lock, right? Muchun, Thanks. > > Signed-off-by: Qi Zheng > --- > mm/mremap.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 24712f8dbb6b5..16e54151395ad 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -143,6 +143,7 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, > spinlock_t *old_ptl, *new_ptl; > bool force_flush = false; > unsigned long len = old_end - old_addr; > + pmd_t pmdval; > int err = 0; > > /* > @@ -175,14 +176,29 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, > err = -EAGAIN; > goto out; > } > - new_pte = pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl); > + /* > + * Since we may free the PTE page in retract_page_tables() without > + * holding the read lock of mmap_lock, so we still need to do a > + * pmd_same() check after holding the PTL. > + */ > + new_pte = pte_offset_map_rw_nolock(mm, new_pmd, new_addr, &pmdval, > + &new_ptl); > if (!new_pte) { > pte_unmap_unlock(old_pte, old_ptl); > err = -EAGAIN; > goto out; > } > - if (new_ptl != old_ptl) > + if (new_ptl != old_ptl) { > spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); > + > + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(new_pmd)))) { > + pte_unmap_unlock(new_pte, new_ptl); > + pte_unmap_unlock(old_pte, old_ptl); > + err = -EAGAIN; > + goto out; > + } > + } > + > flush_tlb_batched_pending(vma->vm_mm); > arch_enter_lazy_mmu_mode(); >