mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-17 01:04:19 +08:00
26bbb29a2a
Jens Axboe's old email address bounces. Signed-off-by: Rob Landley <rob@landley.net> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
89 lines
2.0 KiB
Plaintext
89 lines
2.0 KiB
Plaintext
|
|
struct request documentation
|
|
|
|
Jens Axboe <jens.axboe@oracle.com> 27/05/02
|
|
|
|
1.0
|
|
Index
|
|
|
|
2.0 Struct request members classification
|
|
|
|
2.1 struct request members explanation
|
|
|
|
3.0
|
|
|
|
|
|
2.0
|
|
Short explanation of request members
|
|
|
|
Classification flags:
|
|
|
|
D driver member
|
|
B block layer member
|
|
I I/O scheduler member
|
|
|
|
Unless an entry contains a D classification, a device driver must not access
|
|
this member. Some members may contain D classifications, but should only be
|
|
access through certain macros or functions (eg ->flags).
|
|
|
|
<linux/blkdev.h>
|
|
|
|
2.1
|
|
Member Flag Comment
|
|
------ ---- -------
|
|
|
|
struct list_head queuelist BI Organization on various internal
|
|
queues
|
|
|
|
void *elevator_private I I/O scheduler private data
|
|
|
|
unsigned char cmd[16] D Driver can use this for setting up
|
|
a cdb before execution, see
|
|
blk_queue_prep_rq
|
|
|
|
unsigned long flags DBI Contains info about data direction,
|
|
request type, etc.
|
|
|
|
int rq_status D Request status bits
|
|
|
|
kdev_t rq_dev DBI Target device
|
|
|
|
int errors DB Error counts
|
|
|
|
sector_t sector DBI Target location
|
|
|
|
unsigned long hard_nr_sectors B Used to keep sector sane
|
|
|
|
unsigned long nr_sectors DBI Total number of sectors in request
|
|
|
|
unsigned long hard_nr_sectors B Used to keep nr_sectors sane
|
|
|
|
unsigned short nr_phys_segments DB Number of physical scatter gather
|
|
segments in a request
|
|
|
|
unsigned short nr_hw_segments DB Number of hardware scatter gather
|
|
segments in a request
|
|
|
|
unsigned int current_nr_sectors DB Number of sectors in first segment
|
|
of request
|
|
|
|
unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane
|
|
|
|
int tag DB TCQ tag, if assigned
|
|
|
|
void *special D Free to be used by driver
|
|
|
|
char *buffer D Map of first segment, also see
|
|
section on bouncing SECTION
|
|
|
|
struct completion *waiting D Can be used by driver to get signalled
|
|
on request completion
|
|
|
|
struct bio *bio DBI First bio in request
|
|
|
|
struct bio *biotail DBI Last bio in request
|
|
|
|
struct request_queue *q DB Request queue this request belongs to
|
|
|
|
struct request_list *rl B Request list this request came from
|