The patch titled
Subject: dax: does not work correctly with virtual aliasing caches
has been added to the -mm tree. Its filename is
dax-does-not-work-correctly-with-virtual-aliasing-caches.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/dax-does-not-work-correctly-with-virtual-aliasing-caches.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/dax-does-not-work-correctly-with-virtual-aliasing-caches.patch
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------------------------------------------------------
From: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Subject: dax: does not work correctly with virtual aliasing caches
The DAX code accesses the underlying storage through the kernel's linear
mapping, which may not be cache-coherent with user mappings on ARM, MIPS
or SPARC. Temporarily disable the DAX code until this problem is
resolved.
The original XIP code also had this problem, but it was never noticed.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Cc: Andreas Dilger <andreas.dilger@xxxxxxxxx>
Cc: Boaz Harrosh <boaz@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/dax.txt | 3 +++
fs/Kconfig | 1 +
2 files changed, 4 insertions(+)
diff -puN Documentation/filesystems/dax.txt~dax-does-not-work-correctly-with-virtual-aliasing-caches Documentation/filesystems/dax.txt
--- a/Documentation/filesystems/dax.txt~dax-does-not-work-correctly-with-virtual-aliasing-caches
+++ a/Documentation/filesystems/dax.txt
@@ -82,6 +82,9 @@ Shortcomings
Even if the kernel or its modules are stored on a filesystem that supports
DAX on a block device that supports DAX, they will still be copied into RAM.
+The DAX code does not work correctly on architectures which have virtually
+mapped caches such as ARM, MIPS and SPARC.
+
Calling get_user_pages() on a range of user memory that has been mmaped
from a DAX file will fail as there are no 'struct page' to describe
those pages. This problem is being worked on. That means that O_DIRECT
diff -puN fs/Kconfig~dax-does-not-work-correctly-with-virtual-aliasing-caches fs/Kconfig
--- a/fs/Kconfig~dax-does-not-work-correctly-with-virtual-aliasing-caches
+++ a/fs/Kconfig
@@ -36,6 +36,7 @@ source "fs/nilfs2/Kconfig"
config FS_DAX
bool "Direct Access (DAX) support"
depends on MMU
+ depends on !(ARM || MIPS || SPARC)
help
Direct Access (DAX) can be used on memory-backed block devices.
If the block device supports DAX and the filesystem supports DAX,
_
Patches currently in -mm which might be from matthew.r.wilcox@xxxxxxxxx are
origin.patch
mm-fix-xip-fault-vs-truncate-race.patch
mm-allow-page-fault-handlers-to-perform-the-cow.patch
vfsext2-introduce-is_daxinode.patch
daxext2-replace-xip-read-and-write-with-dax-i-o.patch
daxext2-replace-ext2_clear_xip_target-with-dax_clear_blocks.patch
daxext2-replace-the-xip-page-fault-handler-with-the-dax-page-fault-handler.patch
daxext2-replace-xip_truncate_page-with-dax_truncate_page.patch
vfs-remove-get_xip_mem.patch
ext2-remove-ext2_xip_verify_sb.patch
ext2-remove-ext2_use_xip.patch
ext2-remove-xipc-and-xiph.patch
vfsext2-remove-config_ext2_fs_xip-and-rename-config_fs_xip-to-config_fs_dax.patch
ext2-remove-ext2_aops_xip.patch
ext2-get-rid-of-most-mentions-of-xip-in-ext2.patch
dax-add-dax_zero_page_range.patch
ext4-add-dax-functionality.patch
brd-rename-xip-to-dax.patch
dax-does-not-work-correctly-with-virtual-aliasing-caches.patch
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