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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id o15-20020a05620a2a0f00b006bb49cfe147sm11163767qkp.84.2022.08.31.11.23.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Aug 2022 11:23:18 -0700 (PDT) Date: Wed, 31 Aug 2022 14:23:16 -0400 From: Peter Xu To: David Hildenbrand Cc: John Hubbard , Jason Gunthorpe , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mel Gorman , "Matthew Wilcox (Oracle)" , Andrea Arcangeli , Hugh Dickins , Alistair Popple Subject: Re: [PATCH v1 2/3] mm/gup: use gup_can_follow_protnone() also in GUP-fast Message-ID: References: <20220825164659.89824-1-david@redhat.com> <20220825164659.89824-3-david@redhat.com> <1892f6de-fd22-0e8b-3ff6-4c8641e1c68e@redhat.com> <2e20c90d-4d1f-dd83-aa63-9d8d17021263@redhat.com> <9ce3aaaa-71a6-5a81-16a3-36e6763feb91@redhat.com> <9a4fe603-950e-785b-6281-2e309256463f@nvidia.com> <68b38ac4-c680-b694-21a9-1971396d63b9@redhat.com> <4d067a99-1112-3b3d-bedf-35c1124904fd@redhat.com> MIME-Version: 1.0 In-Reply-To: <4d067a99-1112-3b3d-bedf-35c1124904fd@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661970201; a=rsa-sha256; cv=none; b=nIb7KHiIfcwB1ZDShgcdJnE98FZCh/1MohztPLA4DriijT0/18Qguwd93Z8LQNtvyqq331 S7Fr63xzfb30H7QJt5pN7qg34JpFL1T2O2TvODbd58OR/zenxBdEd1jfCvShUGcu79trB/ P9JP6z2yiEbdMqoadT4QCD3lRdPbZws= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hqj8Wd+U; spf=pass (imf15.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661970201; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2pJGHwIH41qnK/ZRflZS9Bo8zc0dE9GkgGdGB0wqaq8=; b=QGLEGOIy+VgcRxDJcwVG+UYq5mRXMSz7GhYW22XFArCHbXqxIiL8CMYCrBHiGBJ/+94r1/ P+BI2KvmhtTZKoGnyeiGPo1a2Yp5vtKoNJ7eoP1zzJ9FmSo8lcIAiNh6RI4dFim6ysjA5v +9Yt2Ultw2+0FNq51U/zHX4ZU+MocJY= X-Rspam-User: X-Stat-Signature: rx4ru3gpbzty9k4pa97xm8tgnxkmyrqq X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 51273A0040 Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hqj8Wd+U; spf=pass (imf15.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1661970201-574730 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 Wed, Aug 31, 2022 at 06:31:23PM +0200, David Hildenbrand wrote: > >> + /* Clear/invalidate the PTE before checking for PINs. */ > >> + if (IS_ENABLED(CONFIG_HAVE_FAST_GUP)) > >> + smp_mb(); > > > > Wondering whether this could be smp_mb__before_atomic(). > > We'll read via atomic_read(). > > That's a non-RMW operation. smp_mb__before_atomic() only applies to > RMW (Read Modify Write) operations. Ah right. > >> diff --git a/mm/ksm.c b/mm/ksm.c > >> index d7526c705081..971cf923c0eb 100644 > >> --- a/mm/ksm.c > >> +++ b/mm/ksm.c > >> @@ -1091,6 +1091,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, > >> goto out_unlock; > >> } > >> > >> + /* See page_try_share_anon_rmap(): clear PTE first. */ > >> if (anon_exclusive && page_try_share_anon_rmap(page)) { > >> set_pte_at(mm, pvmw.address, pvmw.pte, entry); > >> goto out_unlock; > >> diff --git a/mm/migrate_device.c b/mm/migrate_device.c > >> index 27fb37d65476..47e955212f15 100644 > >> --- a/mm/migrate_device.c > >> +++ b/mm/migrate_device.c > >> @@ -193,20 +193,16 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > >> bool anon_exclusive; > >> pte_t swp_pte; > >> > > > > flush_cache_page() missing here? > > Hmm, wouldn't that already be missing on the !anon path right now? Yes, I think Alistair plans to fix it too in the other patchset. So either this will rebase to that or it should fix it too. Thanks, -- Peter Xu