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 7410AC77B7E for ; Wed, 24 May 2023 03:14:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 10D74280003; Tue, 23 May 2023 23:14:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 096A8280001; Tue, 23 May 2023 23:14:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EA0AC280003; Tue, 23 May 2023 23:14:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id D7B85280001 for ; Tue, 23 May 2023 23:14:34 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id B732AAE1D8 for ; Wed, 24 May 2023 03:14:34 +0000 (UTC) X-FDA: 80823680868.26.5A7952C Received: from out-53.mta0.migadu.com (out-53.mta0.migadu.com [91.218.175.53]) by imf14.hostedemail.com (Postfix) with ESMTP id A882E10000D for ; Wed, 24 May 2023 03:14:32 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=kOtI8EGA; spf=pass (imf14.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.53 as permitted sender) smtp.mailfrom=qi.zheng@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=1684898072; 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=zptm10s4FWGNuDqotiyHNqzSBWdZWYYk5Du9kKCZq8I=; b=Gnh178SCHI4P0S0tYt4EKipIz0lHqk6HIp6aN5rVZxF83SBZo5XTrrxkdJfJyDLqxHYxi2 LFXKq2b4lSmJP+g45vwRkrGjnTKro2frd4tshJ/VyGK9FmWN8hyIFFHI+vq4qUBUzG2CCQ k0ceNKW77kh82cBrRhpv3+JA24MprLM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684898072; a=rsa-sha256; cv=none; b=w+lTrza79EWD66Mx+Jxab7aWaS6DPvERNm0afkmh5AFPtmnJvS2CdNwg90JgNhJg/zpKHv ZbIVVZagman/5gCRGBCn2the2xdWP1RuCmEk9xoR9wTyE6ILg+Zus/Ouwuaw1uo9qnQbrX YRfuQG+iHFfPHq/Sp7WysnhVcHLDysI= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=kOtI8EGA; spf=pass (imf14.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.53 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: <03e44919-fa89-5719-466e-90e7738633aa@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1684898070; 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=zptm10s4FWGNuDqotiyHNqzSBWdZWYYk5Du9kKCZq8I=; b=kOtI8EGAFZbUN6zzUkFOdQ7CpFoauCOESyTYomdMRtcOTlEUhcsE42MNvndJvZOd3gUMQo ejuQdwiPfEqilZ3otUWcc5/SBH9AysOULQNtSrZv6mav4fMXXIROLmhlI87cA/bRHAEHd1 SlYbN19jkfBj7okOi721QZIhvExMeXU= Date: Wed, 24 May 2023 11:14:17 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 05/31] mm/filemap: allow pte_offset_map_lock() to fail Content-Language: en-US To: Hugh Dickins Cc: Andrew Morton , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com> <3e6d4f8-9f4d-fa7e-304e-1494dddd45b@google.com> <8f6057b5-362b-a0f6-2f2f-579debe48fce@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: A882E10000D X-Rspam-User: X-Stat-Signature: gb5tpncz1ffgq3e4bbkaimthxwf8kcky X-Rspamd-Server: rspam03 X-HE-Tag: 1684898072-161620 X-HE-Meta: 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 cPE1F9xg 6fVwM9kMHd9g/6p7r1fM6RwLEKHz+Y6TDeUSNcFepZf8HQuJCth9809H9KY3Nn+IdFB+Dm3RXOHqF1AHsPjHfVhr7947HePsHeUcyen4EogxsAd9b0XMWuH7/ibKFxwX4eskmXVRH1L9QpaYGAz8FD1rIIHOeMa5GVoqb 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: On 2023/5/24 10:35, Hugh Dickins wrote: > On Mon, 22 May 2023, Qi Zheng wrote: >> On 2023/5/22 12:54, Hugh Dickins wrote: >>> filemap_map_pages() allow pte_offset_map_lock() to fail; and remove the >>> pmd_devmap_trans_unstable() check from filemap_map_pmd(), which can safely >>> return to filemap_map_pages() and let pte_offset_map_lock() discover that. >>> >>> Signed-off-by: Hugh Dickins >>> --- >>> mm/filemap.c | 12 +++++------- >>> 1 file changed, 5 insertions(+), 7 deletions(-) >>> >>> diff --git a/mm/filemap.c b/mm/filemap.c >>> index 28b42ee848a4..9e129ad43e0d 100644 >>> --- a/mm/filemap.c >>> +++ b/mm/filemap.c >>> @@ -3408,13 +3408,6 @@ static bool filemap_map_pmd(struct vm_fault *vmf, >>> struct folio *folio, >>> if (pmd_none(*vmf->pmd)) >>> pmd_install(mm, vmf->pmd, &vmf->prealloc_pte); >>> - /* See comment in handle_pte_fault() */ >>> - if (pmd_devmap_trans_unstable(vmf->pmd)) { >>> - folio_unlock(folio); >>> - folio_put(folio); >>> - return true; >>> - } >>> - >>> return false; >>> } >>> >>> @@ -3501,6 +3494,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, >>> >>> addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT); >>> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl); >>> + if (!vmf->pte) { >>> + folio_unlock(folio); >>> + folio_put(folio); >> >> Missing: >> ret = VM_FAULT_NOPAGE; >> ? > > No, not missed. Here ret is 0, which leads do_read_fault() to try > __do_fault() afterwards. Whereas VM_FAULT_NOPAGE would send it back > to userspace to retry the whole fault. Either will work, but I think > the intention of VM_FAULT_NOPAGE here in filemap_map_pages() is to say > "the page you want is now inserted", which is probably not the case. Got it. Thanks for the explanation. > > Hugh -- Thanks, Qi