About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / block / request.txt




Custom Search

Based on kernel version 3.16. Page generated on 2014-08-06 21:36 EST.

1	
2	struct request documentation
3	
4	Jens Axboe <jens.axboe@oracle.com> 27/05/02
5	
6	1.0
7	Index
8	
9	2.0 Struct request members classification
10	
11		2.1 struct request members explanation
12	
13	3.0
14	
15	
16	2.0
17	Short explanation of request members
18	
19	Classification flags:
20	
21		D	driver member
22		B	block layer member
23		I	I/O scheduler member
24	
25	Unless an entry contains a D classification, a device driver must not access
26	this member. Some members may contain D classifications, but should only be
27	access through certain macros or functions (eg ->flags).
28	
29	<linux/blkdev.h>
30	
31	2.1
32	Member				Flag	Comment
33	------				----	-------
34	
35	struct list_head queuelist	BI	Organization on various internal
36						queues
37	
38	void *elevator_private		I	I/O scheduler private data
39	
40	unsigned char cmd[16]		D	Driver can use this for setting up
41						a cdb before execution, see
42						blk_queue_prep_rq
43	
44	unsigned long flags		DBI	Contains info about data direction,
45						request type, etc.
46	
47	int rq_status			D	Request status bits
48	
49	kdev_t rq_dev			DBI	Target device
50	
51	int errors			DB	Error counts
52	
53	sector_t sector			DBI	Target location
54	
55	unsigned long hard_nr_sectors	B	Used to keep sector sane
56	
57	unsigned long nr_sectors	DBI	Total number of sectors in request
58	
59	unsigned long hard_nr_sectors	B	Used to keep nr_sectors sane
60	
61	unsigned short nr_phys_segments	DB	Number of physical scatter gather
62						segments in a request
63	
64	unsigned short nr_hw_segments	DB	Number of hardware scatter gather
65						segments in a request
66	
67	unsigned int current_nr_sectors	DB	Number of sectors in first segment
68						of request
69	
70	unsigned int hard_cur_sectors	B	Used to keep current_nr_sectors sane
71	
72	int tag				DB	TCQ tag, if assigned
73	
74	void *special			D	Free to be used by driver
75	
76	char *buffer			D	Map of first segment, also see
77						section on bouncing SECTION
78	
79	struct completion *waiting	D	Can be used by driver to get signalled
80						on request completion
81	
82	struct bio *bio			DBI	First bio in request
83	
84	struct bio *biotail		DBI	Last bio in request
85	
86	struct request_queue *q		DB	Request queue this request belongs to
87	
88	struct request_list *rl		B	Request list this request came from
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.