From d92576f1167cacf7844e5993f343eed4a6d8a147 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox <matthew.r.wilcox@intel.com> Date: Mon, 16 Feb 2015 15:59:44 -0800 Subject: [PATCH] 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> --- Documentation/filesystems/dax.txt | 3 +++ fs/Kconfig | 1 + 2 files changed, 4 insertions(+) diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt index be376d91d0585..baf41118660d6 100644 --- a/Documentation/filesystems/dax.txt +++ b/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 --git a/fs/Kconfig b/fs/Kconfig index 5331497d5b254..ec35851e5b71c 100644 --- a/fs/Kconfig +++ b/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, -- 2.39.5