[PATCH v3 0/3] Support memory hot-delete to boot memory

[Toshi Kani <toshi.kani@hp.com>]

Memory hot-delete to a memory range present at boot causes an
error message in __release_region(), such as:

 Trying to free nonexistent resource <0000000070000000-0000000077ffffff>

Hot-delete operation still continues since __release_region() is 
a void function, but the target memory range is not freed from
iomem_resource as the result.  This also leads a failure in a 
subsequent hot-add operation to the same memory range since the
address range is still in-use in iomem_resource.

This problem happens because the granularity of memory resource ranges
may be different between boot and hot-delete.  During bootup,
iomem_resource is set up from the boot descriptor table, such as EFI
Memory Table and e820.  Each resource entry usually covers the whole
contiguous memory range.  Hot-delete request, on the other hand, may
target to a particular range of memory resource, and its size can be
much smaller than the whole contiguous memory.  Since the existing
release interfaces like __release_region() require a requested region
to be exactly matched to a resource entry, they do not allow a partial
resource to be released.

This patchset introduces release_mem_region_adjustable() for memory
hot-delete operations, which allows releasing a partial memory range
and adjusts remaining resource accordingly.  This patchset makes no
changes to the existing interfaces since their restriction is still
valid for I/O resources.

---
v3:
- Added #ifdef CONFIG_MEMORY_HOTPLUG to release_mem_region_adjustable()
  as suggested by Andrew Morton.  This #ifdef will be changed to
  CONFIG_MEMORY_HOTREMOVE after David Rientjes's patch gets accepted.
- Updated comments & change log of release_mem_region_adjustable()
  per code reviews from Ram Pai and Andrew Morton. 

v2:
- Updated release_mem_region_adjustable() per code reviews from
  Yasuaki Ishimatsu, Ram Pai and Gu Zheng. 

---
Toshi Kani (3):
 resource: Add __adjust_resource() for internal use
 resource: Add release_mem_region_adjustable()
 mm: Change __remove_pages() to call release_mem_region_adjustable()

---
 include/linux/ioport.h |   4 ++
 kernel/resource.c      | 135 ++++++++++++++++++++++++++++++++++++++++++++-----
 mm/memory_hotplug.c    |  11 +++-
 3 files changed, 135 insertions(+), 15 deletions(-)

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