• Mike Kravetz's avatar
    hugetlbfs: revert "use i_mmap_rwsem for more pmd sharing synchronization" · ddeaab32
    Mike Kravetz authored
    This reverts b43a9990
    
    The reverted commit caused issues with migration and poisoning of anon
    huge pages.  The LTP move_pages12 test will cause an "unable to handle
    kernel NULL pointer" BUG would occur with stack similar to:
    
      RIP: 0010:down_write+0x1b/0x40
      Call Trace:
        migrate_pages+0x81f/0xb90
        __ia32_compat_sys_migrate_pages+0x190/0x190
        do_move_pages_to_node.isra.53.part.54+0x2a/0x50
        kernel_move_pages+0x566/0x7b0
        __x64_sys_move_pages+0x24/0x30
        do_syscall_64+0x5b/0x180
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    The purpose of the reverted patch was to fix some long existing races
    with huge pmd sharing.  It used i_mmap_rwsem for this purpose with the
    idea that this could also be used to address truncate/page fault races
    with another patch.  Further analysis has determined that i_mmap_rwsem
    can not be used to address all these hugetlbfs synchronization issues.
    Therefore, revert this patch while working an another approach to the
    underlying issues.
    
    Link: http://lkml.kernel.org/r/20190103235452.29335-2-mike.kravetz@oracle.comSigned-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
    Reported-by: default avatarJan Stancek <jstancek@redhat.com>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    ddeaab32
userfaultfd.c 16 KB