EXTENT_BUFFER_WRITEBACK
while (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
clear_and_wake_up_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
return (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_WRITEBACK,