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Subject[PATCH v4 0/6] solve deadlock caused by memory allocation with I/O
This patchset try to solve one deadlock problem which might be caused
by memory allocation with block I/O during runtime PM 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 the deadlock
problem on block device/network device during runtime PM 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 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.

Change logs:
- patches from the 2nd to the 6th changed
- call pm_runtime_set_memalloc_noio() after device_add() as pointed
by Alan
- set PF_MEMALLOC_NOIO during runtime_suspend()

- 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
- 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
- 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 | 9 +++++
drivers/base/power/runtime.c | 89 +++++++++++++++++++++++++++++++++++++++++-
drivers/usb/core/hub.c | 13 ++++++
include/linux/pm.h | 1 +
include/linux/pm_runtime.h | 3 ++
include/linux/sched.h | 10 +++++
mm/page_alloc.c | 10 ++++-
mm/vmscan.c | 12 ++++++
net/core/net-sysfs.c | 5 +++

Ming Lei

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