request.txt
2.03 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
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