data cache.
This issue is found by Guo Ren. Based on the Documentation/core-api/cachetlb.rst
and it says:

"Any necessary cache flushing or other coherency operations
that need to occur should happen here.  If the processor's
instruction cache does not snoop cpu stores, it is very
likely that you will need to flush the instruction cache
for copy_to_user_page()."

"If the icache does not snoop stores then this
routine(flush_icache_range) will need to flush it."

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

It broke the 'allmodconfig' build.
fs/xfs/xfs_buf.c: In function 'xfs_buf_bio_end_io':
fs/xfs/xfs_buf.c:1242:3: error: implicit declaration of function 'invalidate_kernel_vmap_range' [-Werror=implicit-function-declaration]
   invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/xfs/xfs_buf.c: In function 'xfs_buf_ioapply_map':
fs/xfs/xfs_buf.c:1312:4: error: implicit declaration of function 'flush_kernel_vmap_range' [-Werror=implicit-function-declaration]
    flush_kernel_vmap_range(bp->b_addr,
    ^~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.

[willy@infradead.org: fix nds32, fs/dax.c]
  Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch contains cache and TLB maintenance functions.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>