From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) (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 26D672034C087 for ; Thu, 19 Oct 2017 19:41:53 -0700 (PDT) Subject: [PATCH v3 02/13] dax: require 'struct page' for filesystem dax From: Dan Williams Date: Thu, 19 Oct 2017 19:39:07 -0700 Message-ID: <150846714747.24336.14704246566580871364.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> References: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: akpm@linux-foundation.org Cc: Jan Kara , linux-nvdimm@lists.01.org, Benjamin Herrenschmidt , Heiko Carstens , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Paul Mackerras , Michael Ellerman , Martin Schwidefsky , linux-fsdevel@vger.kernel.org, hch@lst.de, Gerald Schaefer List-ID: 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. This impacts the dax drivers that do not use dev_memremap_pages(): brd, dcssblk, and axonram. 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 --- arch/powerpc/sysdev/axonram.c | 1 + drivers/dax/super.c | 7 +++++++ drivers/s390/block/dcssblk.c | 1 + 3 files changed, 9 insertions(+) diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c index c60e84e4558d..9da64d95e6f1 100644 --- a/arch/powerpc/sysdev/axonram.c +++ b/arch/powerpc/sysdev/axonram.c @@ -172,6 +172,7 @@ static size_t axon_ram_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, static const struct dax_operations axon_ram_dax_ops = { .direct_access = axon_ram_dax_direct_access, + .copy_from_iter = axon_ram_copy_from_iter, }; diff --git a/drivers/dax/super.c b/drivers/dax/super.c index b0cc8117eebe..26c324a5aef4 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize) return len < 0 ? len : -EIO; } + if (!pfn_t_devmap(pfn)) { + 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/dcssblk.c b/drivers/s390/block/dcssblk.c index 7abb240847c0..e7e5db07e339 100644 --- a/drivers/s390/block/dcssblk.c +++ b/drivers/s390/block/dcssblk.c @@ -52,6 +52,7 @@ static size_t dcssblk_dax_copy_from_iter(struct dax_device *dax_dev, static const struct dax_operations dcssblk_dax_ops = { .direct_access = dcssblk_dax_direct_access, + .copy_from_iter = dcssblk_dax_copy_from_iter, }; _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752406AbdJTCpg (ORCPT ); Thu, 19 Oct 2017 22:45:36 -0400 Received: from mga09.intel.com ([134.134.136.24]:47993 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752324AbdJTCpd (ORCPT ); Thu, 19 Oct 2017 22:45:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,404,1503385200"; d="scan'208";a="325438219" Subject: [PATCH v3 02/13] dax: require 'struct page' for filesystem dax From: Dan Williams To: akpm@linux-foundation.org Cc: Jan Kara , linux-nvdimm@lists.01.org, Benjamin Herrenschmidt , Heiko Carstens , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Jeff Moyer , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , linux-fsdevel@vger.kernel.org, Ross Zwisler , hch@lst.de, Gerald Schaefer Date: Thu, 19 Oct 2017 19:39:07 -0700 Message-ID: <150846714747.24336.14704246566580871364.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> References: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. This impacts the dax drivers that do not use dev_memremap_pages(): brd, dcssblk, and axonram. 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 --- arch/powerpc/sysdev/axonram.c | 1 + drivers/dax/super.c | 7 +++++++ drivers/s390/block/dcssblk.c | 1 + 3 files changed, 9 insertions(+) diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c index c60e84e4558d..9da64d95e6f1 100644 --- a/arch/powerpc/sysdev/axonram.c +++ b/arch/powerpc/sysdev/axonram.c @@ -172,6 +172,7 @@ static size_t axon_ram_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, static const struct dax_operations axon_ram_dax_ops = { .direct_access = axon_ram_dax_direct_access, + .copy_from_iter = axon_ram_copy_from_iter, }; diff --git a/drivers/dax/super.c b/drivers/dax/super.c index b0cc8117eebe..26c324a5aef4 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize) return len < 0 ? len : -EIO; } + if (!pfn_t_devmap(pfn)) { + 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/dcssblk.c b/drivers/s390/block/dcssblk.c index 7abb240847c0..e7e5db07e339 100644 --- a/drivers/s390/block/dcssblk.c +++ b/drivers/s390/block/dcssblk.c @@ -52,6 +52,7 @@ static size_t dcssblk_dax_copy_from_iter(struct dax_device *dax_dev, static const struct dax_operations dcssblk_dax_ops = { .direct_access = dcssblk_dax_direct_access, + .copy_from_iter = dcssblk_dax_copy_from_iter, }; From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: [PATCH v3 02/13] dax: require 'struct page' for filesystem dax From: Dan Williams To: akpm@linux-foundation.org Cc: Jan Kara , linux-nvdimm@lists.01.org, Benjamin Herrenschmidt , Heiko Carstens , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Jeff Moyer , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , linux-fsdevel@vger.kernel.org, Ross Zwisler , hch@lst.de, Gerald Schaefer Date: Thu, 19 Oct 2017 19:39:07 -0700 Message-ID: <150846714747.24336.14704246566580871364.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> References: <150846713528.24336.4459262264611579791.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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. This impacts the dax drivers that do not use dev_memremap_pages(): brd, dcssblk, and axonram. 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 --- arch/powerpc/sysdev/axonram.c | 1 + drivers/dax/super.c | 7 +++++++ drivers/s390/block/dcssblk.c | 1 + 3 files changed, 9 insertions(+) diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c index c60e84e4558d..9da64d95e6f1 100644 --- a/arch/powerpc/sysdev/axonram.c +++ b/arch/powerpc/sysdev/axonram.c @@ -172,6 +172,7 @@ static size_t axon_ram_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, static const struct dax_operations axon_ram_dax_ops = { .direct_access = axon_ram_dax_direct_access, + .copy_from_iter = axon_ram_copy_from_iter, }; diff --git a/drivers/dax/super.c b/drivers/dax/super.c index b0cc8117eebe..26c324a5aef4 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize) return len < 0 ? len : -EIO; } + if (!pfn_t_devmap(pfn)) { + 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/dcssblk.c b/drivers/s390/block/dcssblk.c index 7abb240847c0..e7e5db07e339 100644 --- a/drivers/s390/block/dcssblk.c +++ b/drivers/s390/block/dcssblk.c @@ -52,6 +52,7 @@ static size_t dcssblk_dax_copy_from_iter(struct dax_device *dax_dev, static const struct dax_operations dcssblk_dax_ops = { .direct_access = dcssblk_dax_direct_access, + .copy_from_iter = dcssblk_dax_copy_from_iter, }; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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