Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d92576f1 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

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: default avatarMatthew 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus 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,