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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4E5BC433DB for ; Tue, 19 Jan 2021 20:23:49 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4563923104 for ; Tue, 19 Jan 2021 20:23:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4563923104 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=v8Ly+XOnKcYo3cBc4uf2Xx5HxjdXsAHzMgjHp0ty0OM=; b=rArd1UWvgCwo1xU+qhJ8g8oX9 I5BVMSxOLcX/z4nH4bCeNWf9jtQJKUfOqoC/P6+kjj3V1pW5uMq+Xp2eWlrcrtFtpqqe7AlZd3fXU rSPMdz70OTz0NSGg2WyPuVO7bnMYReaxHUlJah8tpT3DQvSsqGRQgfFPuS3fiFjqhcqUsW3dQuuG4 iZ72fXP8dEGUAKGRBC+9VdZN4oBuGeFrjkZHAfZO5F+ZfOVOYga5fGWAjIu1Knv8gDsBWgBoYsIPd hvvVXrkpOzzVPqENCU/6o3D7W8IK7G+qpFlrTfl5nAv6UU+Pq1eAWOyV7qmQuMTziKxPynPO9uId9 KebP986uw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l1xX8-0007q1-Lx; Tue, 19 Jan 2021 20:23:22 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l1xX6-0007pj-13; Tue, 19 Jan 2021 20:23:20 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3skarH8usgooZsIjjZg9m11Y8vaFLaunY8jfnB6wGPQ=; b=IcFHUlBLm4M8B7XITZrlaPwJZk PxLbfPfkfkOKcDtLlhfkXiUHka5CvTPb7hLgrgmT3Ja+UqcHjN9zY1H6Tmg+WZOu5IRktFRwdo/cS V9j3hg1Ow8RITENXtDtJLmBCwghrrgT8ZPHCKw/4HQvv4xpai+rfbtNKnht6rSRWFZHmep0AFdaLc WpT0BIFZXKaOI1hvNwPxLTcH2Gpj0LlBuWbpsOxA9rDZtRWPCXjXziJFZX6g2OZYB33LP00RMcFkb 3de7nf3N03r6bUtfXPBA8XywS5tDj8kVNevPplCpPm+FZKgebPUFH+9MEl3Zc+oBbVK/fmh04LESS xKXNl/dg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1l1xW1-00EmeP-RV; Tue, 19 Jan 2021 20:22:22 +0000 Date: Tue, 19 Jan 2021 20:22:13 +0000 From: Matthew Wilcox To: Mike Rapoport Subject: Re: [PATCH v14 05/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <20210119202213.GI2260413@casper.infradead.org> References: <20201203062949.5484-1-rppt@kernel.org> <20201203062949.5484-6-rppt@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201203062949.5484-6-rppt@kernel.org> X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , David Hildenbrand , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, "H. Peter Anvin" , Christopher Lameter , Shuah Khan , Thomas Gleixner , Elena Reshetova , linux-arch@vger.kernel.org, Tycho Andersen , linux-nvdimm@lists.01.org, Will Deacon , x86@kernel.org, linux-riscv@lists.infradead.org, Mike Rapoport , Ingo Molnar , Michael Kerrisk , Arnd Bergmann , James Bottomley , Hagen Paul Pfeifer , Borislav Petkov , Alexander Viro , Andy Lutomirski , Paul Walmsley , "Kirill A. Shutemov" , Dan Williams , linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , linux-fsdevel@vger.kernel.org, Shakeel Butt , Andrew Morton , Rick Edgecombe , Roman Gushchin Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, Dec 03, 2020 at 08:29:44AM +0200, Mike Rapoport wrote: > +static vm_fault_t secretmem_fault(struct vm_fault *vmf) > +{ > + struct address_space *mapping = vmf->vma->vm_file->f_mapping; > + struct inode *inode = file_inode(vmf->vma->vm_file); > + pgoff_t offset = vmf->pgoff; > + vm_fault_t ret = 0; > + unsigned long addr; > + struct page *page; > + int err; > + > + if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) > + return vmf_error(-EINVAL); > + > + page = find_get_page(mapping, offset); > + if (!page) { > + > + page = secretmem_alloc_page(vmf->gfp_mask); > + if (!page) > + return vmf_error(-ENOMEM); Just use VM_FAULT_OOM directly. > + err = add_to_page_cache(page, mapping, offset, vmf->gfp_mask); > + if (unlikely(err)) > + goto err_put_page; What if the error is EEXIST because somebody else raced with you to add a new page to the page cache? > + err = set_direct_map_invalid_noflush(page, 1); > + if (err) > + goto err_del_page_cache; Does this work correctly if somebody else has a reference to the page in the meantime? > + addr = (unsigned long)page_address(page); > + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > + > + __SetPageUptodate(page); Once you've added it to the cache, somebody else can come along and try to lock it. They will set PageWaiter. Now you call __SetPageUptodate and wipe out their PageWaiter bit. So you won't wake them up when you unlock. You can call __SetPageUptodate before adding it to the page cache, but once it's visible to another thread, you can't do that. > + ret = VM_FAULT_LOCKED; > + } > + > + vmf->page = page; You're supposed to return the page locked, so use find_lock_page() instead of find_get_page(). > + return ret; > + > +err_del_page_cache: > + delete_from_page_cache(page); > +err_put_page: > + put_page(page); > + return vmf_error(err); > +} _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv