From patchwork Sun Dec 24 00:56:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10131721 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E738E6037D for ; Sun, 24 Dec 2017 01:04:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D727228B11 for ; Sun, 24 Dec 2017 01:04:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CBEAC28F78; Sun, 24 Dec 2017 01:04:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id C989628B11 for ; Sun, 24 Dec 2017 01:04:37 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 0C04A22225C10; Sat, 23 Dec 2017 16:59:46 -0800 (PST) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.31; helo=mga06.intel.com; envelope-from=dan.j.williams@intel.com; receiver=linux-nvdimm@lists.01.org Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 4BE8A222F4E28 for ; Sat, 23 Dec 2017 16:59:45 -0800 (PST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Dec 2017 17:04:36 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,448,1508828400"; d="scan'208";a="5189790" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.16]) by orsmga008.jf.intel.com with ESMTP; 23 Dec 2017 17:04:36 -0800 Subject: [PATCH v4 04/18] dax: require 'struct page' by default for filesystem dax From: Dan Williams To: akpm@linux-foundation.org Date: Sat, 23 Dec 2017 16:56:22 -0800 Message-ID: <151407698249.38751.17338746909239708376.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <151407695916.38751.2866053440557472361.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151407695916.38751.2866053440557472361.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jack@suse.cz, linux-nvdimm@lists.01.org, Benjamin Herrenschmidt , Heiko Carstens , linux-xfs@vger.kernel.org, Martin Schwidefsky , Paul Mackerras , Michael Ellerman , linux-fsdevel@vger.kernel.org, hch@lst.de, Gerald Schaefer Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Virus-Scanned: ClamAV using ClamSMTP If a dax buffer from a device that does not map pages is passed to read(2) or write(2) as a target for direct-I/O it triggers SIGBUS. If gdb attempts to examine the contents of a dax buffer from a device that does not map pages it triggers SIGBUS. If fork(2) is called on a process with a dax mapping from a device that does not map pages it triggers SIGBUS. 'struct page' is required otherwise several kernel code paths break in surprising ways. Disable filesystem-dax on devices that do not map pages. In addition to needing pfn_to_page() to be valid we also require devmap pages. We need this to detect dax pages in the get_user_pages_fast() path and so that we can stop managing the VM_MIXEDMAP flag. For DAX drivers that have not supported get_user_pages() to date we allow them to opt-in to supporting DAX with the CONFIG_FS_DAX_LIMITED configuration option which requires ->direct_access() to return pfn_t_special() pfns. This leaves DAX support in brd disabled and scheduled for removal. Note that when the initial dax support was being merged a few years back there was concern that struct page was unsuitable for use with next generation persistent memory devices. The theoretical concern was that struct page access, being such a hotly used data structure in the kernel, would lead to media wear out. While that was a reasonable conservative starting position it has not held true in practice. We have long since committed to using devm_memremap_pages() to support higher order kernel functionality that needs get_user_pages() and pfn_to_page(). Cc: Jan Kara Cc: Jeff Moyer Cc: Christoph Hellwig Cc: Ross Zwisler Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Gerald Schaefer Signed-off-by: Dan Williams Reviewed-by: Jan Kara Reviewed-by: Christoph Hellwig Reviewed-by: Gerald Schaefer --- arch/powerpc/platforms/Kconfig | 1 + drivers/dax/super.c | 10 ++++++++++ drivers/s390/block/Kconfig | 1 + fs/Kconfig | 7 +++++++ 4 files changed, 19 insertions(+) diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig index 5a96a2763e4a..2ce89b42a9f4 100644 --- a/arch/powerpc/platforms/Kconfig +++ b/arch/powerpc/platforms/Kconfig @@ -297,6 +297,7 @@ config AXON_RAM tristate "Axon DDR2 memory device driver" depends on PPC_IBM_CELL_BLADE && BLOCK select DAX + select FS_DAX_LIMITED default m help It registers one block device per Axon's DDR2 memory bank found diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 3ec804672601..473af694ad1c 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -123,6 +124,15 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize) return len < 0 ? len : -EIO; } + if ((IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) + || pfn_t_devmap(pfn)) + /* pass */; + else { + pr_debug("VFS (%s): error: dax support not enabled\n", + sb->s_id); + return -EOPNOTSUPP; + } + return 0; } EXPORT_SYMBOL_GPL(__bdev_dax_supported); diff --git a/drivers/s390/block/Kconfig b/drivers/s390/block/Kconfig index 31f014b57bfc..594ae5fc8e9d 100644 --- a/drivers/s390/block/Kconfig +++ b/drivers/s390/block/Kconfig @@ -15,6 +15,7 @@ config BLK_DEV_XPRAM config DCSSBLK def_tristate m select DAX + select FS_DAX_LIMITED prompt "DCSSBLK support" depends on S390 && BLOCK help diff --git a/fs/Kconfig b/fs/Kconfig index 7aee6d699fd6..b40128bf6d1a 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -58,6 +58,13 @@ config FS_DAX_PMD depends on ZONE_DEVICE depends on TRANSPARENT_HUGEPAGE +# Selected by DAX drivers that do not expect filesystem DAX to support +# get_user_pages() of DAX mappings. I.e. "limited" indicates no support +# for fork() of processes with MAP_SHARED mappings or support for +# direct-I/O to a DAX mapping. +config FS_DAX_LIMITED + bool + endif # BLOCK # Posix ACL utility routines