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[209.132.183.28]) by mx.google.com with ESMTPS id p187si3134607qkd.58.2019.02.20.03.49.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Feb 2019 03:49:02 -0800 (PST) Received-SPF: pass (google.com: domain of peterx@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 peterx@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2DC215945B; Wed, 20 Feb 2019 11:49:01 +0000 (UTC) Received: from xz-x1 (ovpn-12-37.pek2.redhat.com [10.72.12.37]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5ACAB17B15; Wed, 20 Feb 2019 11:48:52 +0000 (UTC) Date: Wed, 20 Feb 2019 19:48:49 +0800 From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: David Hildenbrand , Hugh Dickins , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: Re: [PATCH v2 04/26] mm: allow VM_FAULT_RETRY for multiple times Message-ID: <20190220114849.GA4060@xz-x1> References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-5-peterx@redhat.com> <20190213033444.GD11247@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190213033444.GD11247@xz-x1> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 20 Feb 2019 11:49:01 +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 Wed, Feb 13, 2019 at 11:34:44AM +0800, Peter Xu wrote: > On Tue, Feb 12, 2019 at 10:56:10AM +0800, Peter Xu wrote: > > [...] > > > @@ -1351,7 +1351,7 @@ EXPORT_SYMBOL_GPL(__lock_page_killable); > > int __lock_page_or_retry(struct page *page, struct mm_struct *mm, > > unsigned int flags) > > { > > - if (flags & FAULT_FLAG_ALLOW_RETRY) { > > + if (!flags & FAULT_FLAG_TRIED) { > > Sorry, this should be: > > if (!(flags & FAULT_FLAG_TRIED)) Ok this is problematic too... Because we for sure allow the page fault flags to be both !ALLOW_RETRY and !TRIED (e.g., when doing GUP and when __get_user_pages() is with locked==NULL and !FOLL_NOWAIT). So current code will fall through the if condition and call up_read(mmap_sem) even if above condition happened (while we shouldn't because the GUP caller would assume the mmap_sem should be still held). So the correct check should be: if ((flags & FAULT_FLAG_ALLOW_RETRY) && !(flags & FAULT_FLAG_TRIED)) To make things easier, I'll just repost this single patch later. Sorry for the noise. Regards, -- Peter Xu