On Sat, Dec 22, 2018 at 02:30:11PM -0800, Mike Kravetz wrote: > 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, > http://lkml.kernel.org/r/20181024045053.1467-1-mike.kravetz@xxxxxxxxxx > 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 Looks good to me. Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kirill A. Shutemov
