[PATCH 0/7] mm/thp: fix THP splitting unmap BUGs and related

[Hugh Dickins <hughd@google.com>]

Here is a batch of long-standing THP bug fixes that I had not got
around to sending before, but prompted now by Wang Yugui's report
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/

Wang Yugui has tested a rollup of these fixes applied to 5.10.39,
and they have done no harm, but have *not* fixed that issue:
something more is needed and I have no idea of what.

But at least these clear up related issues, and should go to stable
(except for the last, which is just an optimization: it would be
fine in stable, but it's not required there).

These are against 5.13-rc4: easy for others to try out, but my next
task is to work out how to shoehorn them into mmotm and linux-next.

I would have said just before Yang Shi's related
mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch
except that (which should also go to stable) is currently placed after
Alistair Popple's "Add support for SVM atomics in Nouveau" series,
mm-rmap-split-try_to_munlock-from-try_to_unmap.patch etc.
I expect I shall offer you some rediffs of Alistair's, we'll see.

1/7 mm/thp: fix __split_huge_pmd_locked() on shmem migration entry
2/7 mm/thp: try_to_unmap() use TTU_SYNC for safe DEBUG_VM splitting
3/7 mm/thp: fix vma_address() if virtual address below file offset
4/7 mm/thp: fix page_address_in_vma() on file THP tails
5/7 mm/thp: fix page_vma_mapped_walk() if huge page mapped by ptes
6/7 mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page()
7/7 mm/thp: remap_page() is only needed on anonymous THP

 include/linux/mm.h   |    3 
 include/linux/rmap.h |    3 
 mm/huge_memory.c     |   47 ++++++++----
 mm/internal.h        |   54 ++++++++++----
 mm/memory.c          |   40 ++++++++++
 mm/page_vma_mapped.c |  163 ++++++++++++++++++++++++++-----------------
 mm/pgtable-generic.c |    5 -
 mm/rmap.c            |   39 +++++++---
 mm/truncate.c        |   43 +++++------
 9 files changed, 266 insertions(+), 131 deletions(-)

Hugh