The patch titled
Subject: dax: disable filesystem dax on devices that do not map pages
has been added to the -mm tree. Its filename is
dax-disable-filesystem-dax-on-devices-that-do-not-map-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/dax-disable-filesystem-dax-on-devices-that-do-not-map-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/dax-disable-filesystem-dax-on-devices-that-do-not-map-pages.patch
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------------------------------------------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: dax: disable filesystem dax on devices that do not map pages
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.
Link: http://lkml.kernel.org/r/150664807247.36094.11168730579639072446.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/dax/super.c | 7 +++++++
1 file changed, 7 insertions(+)
diff -puN drivers/dax/super.c~dax-disable-filesystem-dax-on-devices-that-do-not-map-pages drivers/dax/super.c
--- a/drivers/dax/super.c~dax-disable-filesystem-dax-on-devices-that-do-not-map-pages
+++ a/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_bl
return len < 0 ? len : -EIO;
}
+ if (!pfn_t_has_page(pfn)) {
+ pr_debug("VFS (%s): error: dax support not enabled\n",
+ sb->s_id);
+ return -EOPNOTSUPP;
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(__bdev_dax_supported);
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
dax-quiet-bdev_dax_supported.patch
dax-disable-filesystem-dax-on-devices-that-do-not-map-pages.patch
dax-stop-using-vm_mixedmap-for-dax.patch
dax-stop-using-vm_hugepage-for-dax.patch
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