April 2012
Intermediate to advanced
352 pages
8h
English
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Block I/O Structures
A bio structure represents a block-centric I/O request. Loosely speaking, when the kernel needs to transfer some data to or from a storage device, it puts together a bio structure to describe that operation; then it passes that structure to the appropriate driver.
struct bio is defined in the <sys/bio.h> header as follows:
struct bio { uint8_t bio_cmd; /* I/O operation. */ uint8_t bio_flags; /* General flags. */ uint8_t bio_cflags; /* Private use by the consumer. */ uint8_t bio_pflags; /* Private use by the provider. */ struct cdev *bio_dev; /* Device to perform I/O on. */ struct disk *bio_disk; /* Disk structure. */ off_t bio_offset; /* Requested position in file. */ long bio_bcount; /* Number of (valid) bytes. */ caddr_t bio_data; ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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