Commit d92576f1 authored Feb 16, 2015 by Matthew Wilcox Committed by Linus Torvalds Feb 16, 2015

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@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a7a97fc9

Documentation/filesystems/dax.txt

+3 −0

Original line number	Diff line number	Diff line
		@@ -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

fs/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -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,

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