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: Zach Brown <zab@zabbo.net>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Tested-by: Sedat Dilek <sedat.dilek@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>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
fs: use read_iter and write_iter rather than aio_read and aio_write

File systems implementing read_iter & write_iter should not be required
to keep aio_read and aio_write as well. The vfs should always call
read/write_iter if they exist. This will make it easier to remove the
aio_read/write operation in the future.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Zach Brown <zab@zabbo.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: linux-aio@kvack.org
fs: add read_iter and write_iter to several file systems

These are the simple ones.

File systems that use generic_file_aio_read() and generic_file_aio_write()
can trivially support generic_file_read_iter() and generic_file_write_iter().

This patch adds those file_operations for 9p, adfs, affs, bfs, exofs, ext2,
ext3, fat, f2fs, hfs, hfsplus, hostfs, hpfs, jfs, jffs2, logfs, minix, nilfs2,
omfs, ramfs, reiserfs, romfs, sysv, and ufs.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Boaz Harrosh <bharrosh@panasas.com>
Cc: Zach Brown <zab@zabbo.net>
ocfs2: add support for read_iter and write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Joel Becker <jlbec@evilplan.org>
Cc: Zach Brown <zab@zabbo.net>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: ocfs2-devel@oss.oracle.com
ext4: add support for read_iter and write_iter

use the generic_file_read_iter(), create ext4_file_write_iter() based on
ext4_file_write(), and make ext4_file_write() a wrapper around
ext4_file_write_iter().

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Zach Brown <zab@zabbo.net>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
nfs: add support for read_iter, write_iter

This patch implements the read_iter and write_iter file operations which
allow kernel code to initiate directIO. This allows the loop device to
read and write directly to the server, bypassing the page cache.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: linux-nfs@vger.kernel.org
nfs: simplify swap

swap_writepage can now call nfs's write_iter f_op, eliminating the need to
implement for the special-case direct_IO a_op. There is no longer a need to
pass the uio flag through the direct write path.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: linux-nfs@vger.kernel.org
btrfs: add support for read_iter and write_iter

btrfs can use generic_file_read_iter(). Base btrfs_file_write_iter()
on btrfs_file_aio_write(), then have the latter call the former.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: linux-btrfs@vger.kernel.org
block_dev: add support for read_iter, write_iter

Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
xfs: add support for read_iter and write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Ben Myers <bpm@sgi.com>
Cc: Alex Elder <elder@kernel.org>
Cc: xfs@oss.sgi.com
gfs2: Convert aio_read/write ops to read/write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: cluster-devel@redhat.com
udf: convert file ops from aio_read/write to read/write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Acked-by: Jan Kara <jack@suse.cz>
afs: add support for read_iter and write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Cc: linux-afs@lists.infradead.org
ecrpytfs: Convert aio_read/write ops to read/write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Dustin Kirkland <dustin.kirkland@gazzang.com>
Cc: ecryptfs@vger.kernel.org
ubifs: convert file ops from aio_read/write to read/write_iter

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: linux-mtd@lists.infradead.org
tmpfs: add support for read_iter and write_iter

Convert tmpfs do_shmem_file_read() to shmem_file_read_iter().
Make file_read_iter_actor() global so tmpfs can use it too: delete
file_read_actor(), which was made global in 2.4.4 for use by tmpfs.
Replace tmpfs generic_file_aio_write() by generic_file_write_iter().

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>