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From: Dan Williams <dan.j.williams@intel.com>
To: akpm@linux-foundation.org
Cc: Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: [PATCH 1/3] dax: disable filesystem dax on devices that do not map pages
Date: Wed, 27 Sep 2017 16:49:43 -0700	[thread overview]
Message-ID: <150655618343.700.16350109614227108839.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In-Reply-To: <150655617774.700.5326522538400299973.stgit@dwillia2-desk3.amr.corp.intel.com>

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.

Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/super.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 30d8a5aedd23..d9ac57b3e49a 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -15,6 +15,7 @@
 #include <linux/mount.h>
 #include <linux/magic.h>
 #include <linux/genhd.h>
+#include <linux/pfn_t.h>
 #include <linux/cdev.h>
 #include <linux/hash.h>
 #include <linux/slab.h>
@@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
 		return len < 0 ? len : -EIO;
 	}
 
+	if (!pfn_t_has_page(pfn)) {
+		pr_err("VFS (%s): error: dax support not enabled\n",
+				sb->s_id);
+		return -EOPNOTSUPP;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__bdev_dax_supported);

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WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: akpm@linux-foundation.org
Cc: Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org, linux-mm@kvack.org,
	Jeff Moyer <jmoyer@redhat.com>,
	linux-fsdevel@vger.kernel.org,
	Ross Zwisler <ross.zwisler@linux.intel.com>,
	Christoph Hellwig <hch@lst.de>
Subject: [PATCH 1/3] dax: disable filesystem dax on devices that do not map pages
Date: Wed, 27 Sep 2017 16:49:43 -0700	[thread overview]
Message-ID: <150655618343.700.16350109614227108839.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In-Reply-To: <150655617774.700.5326522538400299973.stgit@dwillia2-desk3.amr.corp.intel.com>

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.

Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/super.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 30d8a5aedd23..d9ac57b3e49a 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -15,6 +15,7 @@
 #include <linux/mount.h>
 #include <linux/magic.h>
 #include <linux/genhd.h>
+#include <linux/pfn_t.h>
 #include <linux/cdev.h>
 #include <linux/hash.h>
 #include <linux/slab.h>
@@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
 		return len < 0 ? len : -EIO;
 	}
 
+	if (!pfn_t_has_page(pfn)) {
+		pr_err("VFS (%s): error: dax support not enabled\n",
+				sb->s_id);
+		return -EOPNOTSUPP;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__bdev_dax_supported);

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  reply	other threads:[~2017-09-27 23:52 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-27 23:49 [PATCH 0/3] dax: require 'struct page' and other fixups Dan Williams
2017-09-27 23:49 ` Dan Williams
2017-09-27 23:49 ` Dan Williams [this message]
2017-09-27 23:49   ` [PATCH 1/3] dax: disable filesystem dax on devices that do not map pages Dan Williams
2017-09-28 16:25   ` Jeff Moyer
2017-09-28 16:25     ` Jeff Moyer
2017-09-28 16:25     ` Jeff Moyer
2017-09-28 16:28     ` Dan Williams
2017-09-28 16:28       ` Dan Williams
2017-09-27 23:49 ` [PATCH 2/3] dax: stop using VM_MIXEDMAP for dax Dan Williams
2017-09-27 23:49   ` Dan Williams
2017-09-28  0:09   ` Dan Williams
2017-09-28  0:09     ` Dan Williams
2017-09-28 16:32   ` Jeff Moyer
2017-09-28 16:32     ` Jeff Moyer
2017-09-28 16:32     ` Jeff Moyer
2017-09-28 16:41     ` Dan Williams
2017-09-27 23:49 ` [PATCH 3/3] dax: stop using VM_HUGEPAGE " Dan Williams
2017-09-27 23:49   ` Dan Williams

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