#define READ_SYNC (READ | (1 << BIO_RW_SYNC))
#define READ_META (READ | (1 << BIO_RW_META))
#define WRITE_SYNC (WRITE | (1 << BIO_RW_SYNC))
+#define SWRITE_SYNC (SWRITE | (1 << BIO_RW_SYNC))
#define WRITE_BARRIER ((1 << BIO_RW) | (1 << BIO_RW_BARRIER))
#define SEL_IN 1