AS_ENOSPC
set_bit(AS_ENOSPC, &mapping->flags);
if (test_bit(AS_ENOSPC, &mapping->flags) &&
test_and_clear_bit(AS_ENOSPC, &mapping->flags))
if (test_bit(AS_ENOSPC, &mapping->flags))
clear_bit(AS_ENOSPC, &mapping->flags);