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>
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>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.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>
Cc: v9fs-developer@lists.sourceforge.net
Cc: Tigran A. Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Benny Halevy <bhalevy@tonian.com>
Cc: osd-dev@open-osd.org
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: jfs-discussion@lists.sourceforge.net
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: linux-mtd@lists.infradead.org
Cc: Joern Engel <joern@logfs.org>
Cc: Prasad Joshi <prasadjoshi.linux@gmail.com>
Cc: logfs@logfs.org
Cc: linux-nilfs@vger.kernel.org
Cc: Bob Copeland <me@bobcopeland.com>
Cc: linux-karma-devel@lists.sourceforge.net
Cc: reiserfs-devel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
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>
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
modified for Mako from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>
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
iov_iter: move into its own file (bug fix)

I found the problem. iov_iter_shorten() wasn't setting i->count to the new
value.

This fixes it. I'll fix the patchset tomorrow.

Thanks,
Shaggy
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>
modified for Mako from LKML reference

Signed-off-by: faux123 <reioux@gmail.com>
aio: convert the ioctx list to radix tree

Date	Wed, 3 Apr 2013 16:20:48 +0300

When using a large number of threads performing AIO operations the
IOCTX list may get a significant number of entries which will cause
significant overhead. For example, when running this fio script:

rw=randrw; size=256k ;directory=/mnt/fio; ioengine=libaio; iodepth=1
blocksize=1024; numjobs=512; thread; loops=100

on an EXT2 filesystem mounted on top of a ramdisk we can observe up to
30% CPU time spent by lookup_ioctx:

 32.51%  [guest.kernel]  [g] lookup_ioctx
  9.19%  [guest.kernel]  [g] __lock_acquire.isra.28
  4.40%  [guest.kernel]  [g] lock_release
  4.19%  [guest.kernel]  [g] sched_clock_local
  3.86%  [guest.kernel]  [g] local_clock
  3.68%  [guest.kernel]  [g] native_sched_clock
  3.08%  [guest.kernel]  [g] sched_clock_cpu
  2.64%  [guest.kernel]  [g] lock_release_holdtime.part.11
  2.60%  [guest.kernel]  [g] memcpy
  2.33%  [guest.kernel]  [g] lock_acquired
  2.25%  [guest.kernel]  [g] lock_acquire
  1.84%  [guest.kernel]  [g] do_io_submit

This patchs converts the ioctx list to a radix tree. For a performance
comparison the above FIO script was run on a 2 sockets 8 core
machine. This are the results for the original list based
implementation and for the radix tree based implementation:

cores         1         2         4         8         16        32
list        111025 ms  62219 ms  34193 ms  22998 ms  19335 ms  15956 ms
radix        75400 ms  42668 ms  23923 ms  17206 ms  15820 ms  13295 ms
% of radix
relative      68%       69%       70%       75%       82%       83%
to list

To consider the impact of the patch on the typical case of having
only one ctx per process the following FIO script was run:

rw=randrw; size=100m ;directory=/mnt/fio; ioengine=libaio; iodepth=1
blocksize=1024; numjobs=1; thread; loops=100

on the same system and the results are the following:

list        65241 ms
radix       65402 ms
% of radix
relative    100.25%
to list

Cc: Andi Kleen <ak@linux.intel.com>

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
modified for Mako hybrid from LKML

Signed-off-by: Paul Reioux <reioux@gmail.com>
exfat: AIO Optimization compatibility fixup

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