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[209.132.183.28]) by mx.google.com with ESMTPS id s16si20754969qte.92.2019.07.24.01.57.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 01:57:39 -0700 (PDT) Received-SPF: pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0E1D830C1E3F; Wed, 24 Jul 2019 08:57:39 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 44A8D60BFC; Wed, 24 Jul 2019 08:57:37 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 24 Jul 2019 10:57:38 +0200 (CEST) Date: Wed, 24 Jul 2019 10:57:36 +0200 From: Oleg Nesterov To: Song Liu Cc: lkml , Linux-MM , Matthew Wilcox , "Kirill A. Shutemov" , Peter Zijlstra , Steven Rostedt , Kernel Team , William Kucharski Subject: Re: [PATCH v7 2/4] uprobe: use original page when all uprobes are removed Message-ID: <20190724085736.GA21599@redhat.com> References: <20190625235325.2096441-1-songliubraving@fb.com> <20190625235325.2096441-3-songliubraving@fb.com> <20190715152513.GD1222@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Wed, 24 Jul 2019 08:57:39 +0000 (UTC) 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 07/24, Song Liu wrote: > > > > On Jul 15, 2019, at 8:25 AM, Oleg Nesterov wrote: > > > >> + if (!is_register) { > >> + struct page *orig_page; > >> + pgoff_t index; > >> + > >> + index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT; > >> + orig_page = find_get_page(vma->vm_file->f_inode->i_mapping, > >> + index); > >> + > >> + if (orig_page) { > >> + if (pages_identical(new_page, orig_page)) { > > > > Shouldn't we at least check PageUptodate? > > For page cache, we only do ClearPageUptodate() on read failures, Hmm. I don't think so. > so > this should be really rare case. But I guess we can check anyway. Can? I think we should or this code is simply wrong... > > and I am a bit surprised there is no simple way to unmap the old page > > in this case... > > The easiest way I have found requires flush_cache_page() plus a few > mmu_notifier calls around it. But we need to do this anyway? At least with your patch replace_page() still does this after page_add_file_rmap(). > I think current solution is better than > that, perhaps, I won't argue, > as it saves a page fault. I don't think it matters in this case. Oleg.