Asynchronous Fsync: initial extraction of Async Fsync from HTC

Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:

	drivers/mmc/core/mmc.c

Conflicts:
	fs/Kconfig
Signed-off-by: klozz <xxx.reptar.rawrr.xxx@gmail.com>
 fs/Kconfig: fix warnings

Signed-off-by: Paul Reioux <reioux@gmail.com>
Signed-off-by: klozz <xxx.reptar.rawrr.xxx@gmail.com>
f2fs:data: add AIO optimization

Signed-off-by: klozz <xxx.reptar.rawrr.xxx@gmail.com>
aio: add aio_kernel_() interface

This adds an interface that lets kernel callers submit aio iocbs without
going through the user space syscalls.  This lets kernel callers avoid
the management limits and overhead of the context.  It will also let us
integrate aio operations with other kernel apis that the user space
interface doesn't have access to.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
modified for Mako from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>
loop: use aio to perform io on the underlying file

This uses the new kernel aio interface to process loopback IO by
submitting concurrent direct aio.  Previously loop's IO was serialized
by synchronous processing in a thread.

The aio operations specify the memory for the IO with the bio_vec arrays
directly instead of mappings of the pages.

The use of aio operations is enabled when the backing file supports the
read_iter, write_iter and direct_IO methods.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
modified for Mako from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>
fs: create file_readable() and file_writable() functions

Create functions to simplify if file_ops contain either a read
or aio_read op, or likewise write or aio_write. We will be adding
read_iter and write_iter and don't need to be complicating the code
in multiple places.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
modified for Mako from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>
fix build

Signed-off-by: klozz <xxx.reptar.rawrr.xxx@gmail.com>