rwbs

For tracing observability, the kernel provides a way to describe the type of each I/O using a character string named rwbs. This is defined in the kernel blk_fill_rwbs() function, and uses the characters:

• R: Read
• W: Write
• M: Metadata
• S: Synchronous
• A: Read-ahead
• F: Flush or Force Unit Access • D: Discard
• E: Erase