iov_iter: add bvec support

This adds a set of iov_iter_ops calls which work with memory which is
specified by an array of bio_vec structs instead of an array of iovec
structs.

The big difference is that the pages referenced by the bio_vec elements
are pinned.  They don't need to be faulted in and we can always use
kmap_atomic() to map them one at a time.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
iov_iter: add a shorten call

The generic direct write path wants to shorten its memory vector.  It
does this when it finds that it has to perform a partial write due to
LIMIT_FSIZE.  .direct_IO() always performs IO on all of the referenced
memory because it doesn't have an argument to specify the length of the
IO.

We add an iov_iter operation for this so that the generic path can ask
to shorten the memory vector without having to know what kind it is.
We're happy to shorten the kernel copy of the iovec array, but we refuse
to shorten the bio_vec array and return an error in this case.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
iov_iter: let callers extract iovecs and bio_vecs

direct IO treats memory from user iovecs and memory from arrays of
kernel pages very differently.  User memory is pinned and worked with in
batches while kernel pages are always pinned and don't require
additional processing.

Rather than try and provide an abstraction that includes these
different behaviours we let direct IO extract the memory structs and
hand them to the existing code.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
dio: Convert direct_IO to use iov_iter

Change the direct_IO aop to take an iov_iter argument rather than an iovec.
This will get passed down through most filesystems so that only the
__blockdev_direct_IO helper need be aware of whether user or kernel memory
is being passed to the function.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
dio: add bio_vec support to __blockdev_direct_IO()

The trick here is to initialize the dio state so that do_direct_IO()
consumes the pages we provide and never tries to map user pages.  This
is done by making sure that final_block_in_request covers the page that
we set in the dio.  do_direct_IO() will return before running out of
pages.

The caller is responsible for dirtying these pages, if needed.  We add
an option to the dio struct that makes sure we only dirty pages when
we're operating on iovecs of user addresses.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
fs: pull iov_iter use higher up the stack

Right now only callers of generic_perform_write() pack their iovec
arguments into an iov_iter structure.  All the callers higher up in the
stack work on raw iovec arguments.

This patch introduces the use of the iov_iter abstraction higher up the
stack.  Private generic path functions are changed to operation on
iov_iter instead of on raw iovecs.  Exported interfaces that take iovecs
immediately pack their arguments into an iov_iter and call into the
shared functions.

File operation struct functions are added with iov_iter as an argument
so that callers to the generic file system functions can specify
abstract memory rather than iovec arrays only.

Almost all of this patch only transforms arguments and shouldn't change
functionality.  The buffered read path is the exception.  We add a
read_actor function which uses the iov_iter helper functions instead of
operating on each individual iovec element.  This may improve
performance as the iov_iter helper can copy multiple iovec elements from
one mapped page cache page.

As always, the direct IO path is special.  Sadly, it may still be
cleanest to have it work on the underlying memory structures directly
instead of working through the iov_iter abstraction.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
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>
aio: add aio support for iov_iter arguments

This adds iocb cmds which specify that memory is held in iov_iter
structures.  This lets kernel callers specify memory that can be
expressed in an iov_iter, which includes pages in bio_vec arrays.

Only kernel callers can provide an iov_iter so it doesn't make a lot of
sense to expose the IOCB_CMD values for this as part of the user space
ABI.

But kernel callers should also be able to perform the usual aio
operations which suggests using the the existing operation namespace and
support code.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
bio: add bvec_length(), like iov_length()

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

ocfs2's .aio_read and .aio_write methods are changed to take
iov_iter and pass it to generic functions.  Wrappers are made to pack
the iovecs into iters and call these new functions.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Cc: Zach Brown <zab@zabbo.net>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
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>
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>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: linux-nfs@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
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>
Cc: Ben Myers <bpm@sgi.com>
Cc: Alex Elder <elder@kernel.org>
Cc: xfs@oss.sgi.com