[PATCH v2 0/4] block & aio: improve loop with kernel aio

[Ming Lei <ming.lei@canonical.com>]

Hi Guys,

The 1st two patches introduce kernel AIO support, most of
is borrowed from previous Dave's work, and thanks to ITER_BVEC,
it is much simper to implement kernel AIO now.

The last two patches applies kernel aio to loop-mq.

Follows benefits from using kernel aio in loop:
	- avoid double cache, and memory usage decreased a lot
	- system load gets much decreased

In the commit log of patch 4, detailed performance data
and system resource monitor information is provided about
using kernel aio for loop block.

V2:
	- remove 'extra' parameter to aio_kernel_alloc()
	- try to avoid memory allcation inside queue req callback
	- introduce 'use_mq' sysfs file for enabling kernel aio or disabling it
V1:
	- link:
		http://marc.info/?t=140803157700004&r=1&w=2
	- improve failure path in aio_kernel_submit()

 drivers/block/loop.c |  173 ++++++++++++++++++++++++++++++++++++++++++++++++--
 drivers/block/loop.h |   11 ++++
 fs/aio.c             |  121 +++++++++++++++++++++++++++++++++++
 fs/direct-io.c       |    9 ++-
 include/linux/aio.h  |   17 ++++-
 5 files changed, 323 insertions(+), 8 deletions(-)


Thanks,
Ming Lei