mmap_lock_speculate_try_begin
if (mmap_lock_speculate_try_begin(mm, &seq)) {
if (!mmap_lock_speculate_try_begin(mm, &seq))
if (!mmap_lock_speculate_try_begin(mm, &seq))
mmap_unlocked = mmap_lock_speculate_try_begin(mm, &mm_wr_seq);