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Subject[PATCH v3 0/2] hugetlbfs: use i_mmap_rwsem for better synchronization
There are two primary issues addressed here:
1) For shared pmds, huge PTE 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.

v2 -> v3
Incorporated suggestions from Kirill. Code change to hold i_mmap_rwsem
for duration of copy in copy_hugetlb_page_range. Took i_mmap_rwsem in
hugetlbfs_evict_inode to be consistent with other callers. Other changes
were to documentation/comments.
v1 -> v2
Combined patches 2 and 3 of v1 series as suggested by Aneesh. No other
changes were made.
Patches are a follow up to the RFC,
Comments made by Naoya were addressed.

Mike Kravetz (2):
hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization
hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race

fs/hugetlbfs/inode.c | 61 +++++++++++++++-----------------
mm/hugetlb.c | 84 +++++++++++++++++++++++++++++++-------------
mm/memory-failure.c | 14 +++++++-
mm/migrate.c | 13 ++++++-
mm/rmap.c | 4 +++
mm/userfaultfd.c | 11 ++++--
6 files changed, 125 insertions(+), 62 deletions(-)


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