[PATCH v2 0/2] Change PAT to support mremap use-cases

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

This patch-set fixes two issues found in PAT when mremap() is used on
a VM_PFNMAP range.

Patch 1/2 fixes an issue for mremap() with MREMAP_FIXED, which moves
a pfnmap from old vma to new vma.  untrack_pfn_moved() is added to
clear VM_PAT from old vma.

Patch 2/2 fixes an issue for mremap() with a shrinking map size.
The free_memtype() path is changed to support this mremap case in
addition to the regular munmap case. 

Note, using mremap() with an expanded map size is not a valid case
since VM_DONTEXPAND is set along with VM_PFNMAP.

v2:
 - Add an explicit call in the mremap code which clears the PAT flag.
   (Thomas Gleixner)
 - Add comment to explain how memtype_rb_match() is used for shrinking
   case. (Thomas Gleixner)

---
Toshi Kani (2):
 1/2 x86/mm/pat: Add untrack_pfn_moved for mremap
 2/2 x86/mm/pat: Change free_memtype() to support shrinking case

---
 arch/x86/mm/pat.c             | 12 +++++++++-
 arch/x86/mm/pat_rbtree.c      | 52 +++++++++++++++++++++++++++++++++++--------
 include/asm-generic/pgtable.h | 10 ++++++++-
 mm/mremap.c                   |  4 ++++
 4 files changed, 67 insertions(+), 11 deletions(-)

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