1 /*
2  * Copyright (C) 2003 Sistina Software
3  * Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
4  *
5  * Device-Mapper low-level I/O.
6  *
7  * This file is released under the GPL.
8  */
9 
10 #ifndef _LINUX_DM_IO_H
11 #define _LINUX_DM_IO_H
12 
13 #ifdef __KERNEL__
14 
15 #include <linux/types.h>
16 
17 struct dm_io_region {
18 	struct block_device *bdev;
19 	sector_t sector;
20 	sector_t count;		/* If this is zero the region is ignored. */
21 };
22 
23 struct page_list {
24 	struct page_list *next;
25 	struct page *page;
26 };
27 
28 typedef void (*io_notify_fn)(unsigned long error, void *context);
29 
30 enum dm_io_mem_type {
31 	DM_IO_PAGE_LIST,/* Page list */
32 	DM_IO_BVEC,	/* Bio vector */
33 	DM_IO_VMA,	/* Virtual memory area */
34 	DM_IO_KMEM,	/* Kernel memory */
35 };
36 
37 struct dm_io_memory {
38 	enum dm_io_mem_type type;
39 
40 	unsigned offset;
41 
42 	union {
43 		struct page_list *pl;
44 		struct bio_vec *bvec;
45 		void *vma;
46 		void *addr;
47 	} ptr;
48 };
49 
50 struct dm_io_notify {
51 	io_notify_fn fn;	/* Callback for asynchronous requests */
52 	void *context;		/* Passed to callback */
53 };
54 
55 /*
56  * IO request structure
57  */
58 struct dm_io_client;
59 struct dm_io_request {
60 	int bi_rw;			/* READ|WRITE - not READA */
61 	struct dm_io_memory mem;	/* Memory to use for io */
62 	struct dm_io_notify notify;	/* Synchronous if notify.fn is NULL */
63 	struct dm_io_client *client;	/* Client memory handler */
64 };
65 
66 /*
67  * For async io calls, users can alternatively use the dm_io() function below
68  * and dm_io_client_create() to create private mempools for the client.
69  *
70  * Create/destroy may block.
71  */
72 struct dm_io_client *dm_io_client_create(unsigned num_pages);
73 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client);
74 void dm_io_client_destroy(struct dm_io_client *client);
75 
76 /*
77  * IO interface using private per-client pools.
78  * Each bit in the optional 'sync_error_bits' bitset indicates whether an
79  * error occurred doing io to the corresponding region.
80  */
81 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
82 	  struct dm_io_region *region, unsigned long *sync_error_bits);
83 
84 #endif	/* __KERNEL__ */
85 #endif	/* _LINUX_DM_IO_H */
86