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 BBDE6CD4F5F for ; Thu, 5 Sep 2024 09:26:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E34436B0202; Thu, 5 Sep 2024 05:26:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DE5DB6B0204; Thu, 5 Sep 2024 05:26:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CAD5F6B0205; Thu, 5 Sep 2024 05:26:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id A76BD6B0202 for ; Thu, 5 Sep 2024 05:26:19 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 46044161ACE for ; Thu, 5 Sep 2024 09:26:19 +0000 (UTC) X-FDA: 82530153678.07.486BAA8 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf27.hostedemail.com (Postfix) with ESMTP id 72FCD40003 for ; Thu, 5 Sep 2024 09:26:16 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c5FUB6sP; spf=pass (imf27.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1725528328; 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=nRCI2DeauznMxWvt70Qz7zNit5+Q7VEXvujH0nECZ00=; b=LmMeasFwB8oQGGSQJdy3IsQ8rd4jM3nYmfSWPzt9NUcfwSU5y5A6GkNtWSlwOOKzeNu+jH HXBgT9cCzNyJbYla4MJYTnTbui4/BbwG70D/bRivDdbrV5BNTkytkRYvpEJEmuq35kH9K2 GzndJ4HQdVSvdSdt1K9ZF58al812GiQ= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c5FUB6sP; spf=pass (imf27.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1725528328; a=rsa-sha256; cv=none; b=WzPid1i54o3dhXwCfRBBQtaZ2AEDSFj5VTRxNgpzIHR+aiKfHOmRSFoYHGJgjJGV79IDr1 ZSRZvughI20PVov6q4EhIYRW8NSQAUvYSm9/SLqalVxiG370mxozrbVHCHy8nzfXvuaPXq F/E9iYWsZFO5/N5JmagiJhLDt42cuRs= 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-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 72FCD40003 X-Stat-Signature: db5i6oi3idcum3k3zafigz3cup3jfqey X-HE-Tag: 1725528376-961410 X-HE-Meta: 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 Ytnni8I4 7F3ugY0lcDdiAkhhG+EEU8xyTAgYeONj05mzx7x9GK75aLq0dIR7L00n2IWubCgZX1Dbxg9ibRxw1ienALe8W04RzAdusDeWRnhVI5fhNVdITxbO7xwtX5eGn3oVgxZDtKBGGIy/iYlCk9PHwIDdQ6Nv/3sE9zBeJkqgYJoiJXgZhaq1+QCgGEpEqFDFFstXJ6P+FwTxH7wJvc2ZgiagPcpGViIQHnwpLDO8RykqDW4rejqWDcR94+ZIuCX0W8GjrFCy7mOwbI4oQdSL8NMNoxfBF5rNgHm+muk6j3cl77uBEOLo= 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 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(); >