This patchset try to solve one deadlock problem which might be caused
by memory allocation with block I/O during runtime resume and block device
error handling path. Traditionly, the problem is addressed by passing
GFP_NOIO statically to mm, but that is not a effective solution, see
detailed description in patch 1's commit log.

This patch set introduces one process flag and trys to fix one deadlock
problem on block device/network device during runtime resume or usb bus reset.

The 1st one is the change on include/sched.h and mm.

The 2nd patch introduces the flag of memalloc_noio_resume on 'dev_pm_info',
and pm_runtime_set_memalloc_noio(), so that PM Core can teach mm to not
allocate mm with GFP_IOFS during the runtime_resume callback only on
device with the flag set.

The following 2 patches apply the introduced pm_runtime_set_memalloc_noio()
to mark all devices as memalloc_noio_resume in the path from the block or
network device to the root device in device tree.

The last 2 patches are applied again PM and USB subsystem to demonstrate
how to use the introduced mechanism to fix the deadlock problem.

V3:
	- patch 2/6 and 5/6 changed, see their commit log
	- remove RFC from title since several guys have expressed that
	it is a reasonable solution
V2:
        - remove changes on 'may_writepage' and 'may_swap'(1/6)
        - unset GFP_IOFS in try_to_free_pages() path(1/6)
        - introduce pm_runtime_set_memalloc_noio()
        - only apply the meachnism on block/network device and its ancestors
        for runtime resume context
V1:
        - take Minchan's change to avoid the check in alloc_page hot path
        - change the helpers' style into save/restore as suggested by Alan
        - memory allocation with no io in usb bus reset path for all devices
        as suggested by Greg and Oliver

 block/genhd.c                |    8 ++++
 drivers/base/power/runtime.c |   88 +++++++++++++++++++++++++++++++++++++++++-
 drivers/usb/core/hub.c       |   15 +++++++
 include/linux/pm.h           |    1 +
 include/linux/pm_runtime.h   |    5 +++
 include/linux/sched.h        |   10 +++++
 mm/page_alloc.c              |   10 ++++-
 mm/vmscan.c                  |   12 ++++++
 net/core/net-sysfs.c         |    5 +++
 9 files changed, 152 insertions(+), 2 deletions(-)


Thanks,
--
Ming Lei