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Subject[PATCH 0/3] hugetlbfs: use i_mmap_rwsem for better synchronization
These patches are a follow up to the RFC,
Comments made by Naoya were addressed.

There are two primary issues addressed here:
1) For shared pmds, huge PE pointers returned by huge_pte_alloc can become
invalid via a call to huge_pmd_unshare by another thread.
2) hugetlbfs page faults can race with truncation causing invalid global
reserve counts and state.
Both issues are addressed by expanding the use of i_mmap_rwsem.

These issues have existed for a long time. They can be recreated with a
test program that causes page fault/truncation races. For simple mappings,
this results in a negative HugePages_Rsvd count. If racing with mappings
that contain shared pmds, we can hit "BUG at fs/hugetlbfs/inode.c:444!" or
Oops! as the result of an invalid memory reference.

I broke up the larger RFC into separate patches addressing each issue.
Hopefully, this is easier to understand/review.

Mike Kravetz (3):
hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization
hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race
hugetlbfs: remove unnecessary code after i_mmap_rwsem synchronization

fs/hugetlbfs/inode.c | 50 +++++++++----------------
mm/hugetlb.c | 87 +++++++++++++++++++++++++++++++-------------
mm/memory-failure.c | 14 ++++++-
mm/migrate.c | 13 ++++++-
mm/rmap.c | 3 ++
mm/userfaultfd.c | 11 +++++-
6 files changed, 116 insertions(+), 62 deletions(-)


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