- Modify fs/ntfs/ntfs_readdir() to copy the index root attribute value
  to a buffer so that we can put the search context and unmap the mft
  record before calling the filldir() callback.  We need to do this
  because of NFSd which calls ->lookup() from its filldir callback()
  and this causes NTFS to deadlock as ntfs_lookup() maps the mft record
  of the directory and since ntfs_readdir() has got it mapped already
  ntfs_lookup() deadlocks.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>