- * The below are the various read and write types that we support. Some of
- * them include behavioral modifiers that send information down to the
- * block layer and IO scheduler. Terminology:
- *
- * The block layer uses device plugging to defer IO a little bit, in
- * the hope that we will see more IO very shortly. This increases
- * coalescing of adjacent IO and thus reduces the number of IOs we
- * have to send to the device. It also allows for better queuing,
- * if the IO isn't mergeable. If the caller is going to be waiting
- * for the IO, then he must ensure that the device is unplugged so
- * that the IO is dispatched to the driver.
- *
- * All IO is handled async in Linux. This is fine for background
- * writes, but for reads or writes that someone waits for completion
- * on, we want to notify the block layer and IO scheduler so that they
- * know about it. That allows them to make better scheduling
- * decisions. So when the below references 'sync' and 'async', it
- * is referencing this priority hint.
- *
- * With that in mind, the available types are:
- *
- * READ A normal read operation. Device will be plugged.
- * READ_SYNC A synchronous read. Device is not plugged, caller can
- * immediately wait on this read without caring about
- * unplugging.
- * READA Used for read-ahead operations. Lower priority, and the
- * block layer could (in theory) choose to ignore this
- * request if it runs into resource problems.
- * WRITE A normal async write. Device will be plugged.
- * WRITE_SYNC Synchronous write. Identical to WRITE, but passes down
- * the hint that someone will be waiting on this IO
- * shortly. The write equivalent of READ_SYNC.
- * WRITE_ODIRECT Special case write for O_DIRECT only.
- * WRITE_FLUSH Like WRITE_SYNC but with preceding cache flush.
- * WRITE_FUA Like WRITE_SYNC but data is guaranteed to be on
- * non-volatile media on completion.
- * WRITE_FLUSH_FUA Combination of WRITE_FLUSH and FUA. The IO is preceded
- * by a cache flush and data is guaranteed to be on
- * non-volatile media on completion.
- *
- */
-#define RW_MASK REQ_WRITE
-#define RWA_MASK REQ_RAHEAD
-
-#define READ 0
-#define WRITE RW_MASK
-#define READA RWA_MASK
-#define KERNEL_READ (READ|REQ_KERNEL)
-#define KERNEL_WRITE (WRITE|REQ_KERNEL)
-
-#define READ_SYNC (READ | REQ_SYNC)
-#define WRITE_SYNC (WRITE | REQ_SYNC | REQ_NOIDLE)
-#define WRITE_ODIRECT (WRITE | REQ_SYNC)
-#define WRITE_FLUSH (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH)
-#define WRITE_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FUA)
-#define WRITE_FLUSH_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH | REQ_FUA)
-
-
-/*