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1 | kcopyd |
2 | ====== |
3 | |
4 | Kcopyd provides the ability to copy a range of sectors from one block-device |
5 | to one or more other block-devices, with an asynchronous completion |
6 | notification. It is used by dm-snapshot and dm-mirror. |
7 | |
8 | Users of kcopyd must first create a client and indicate how many memory pages |
9 | to set aside for their copy jobs. This is done with a call to |
10 | kcopyd_client_create(). |
11 | |
12 | int kcopyd_client_create(unsigned int num_pages, |
13 | struct kcopyd_client **result); |
14 | |
15 | To start a copy job, the user must set up io_region structures to describe |
16 | the source and destinations of the copy. Each io_region indicates a |
17 | block-device along with the starting sector and size of the region. The source |
18 | of the copy is given as one io_region structure, and the destinations of the |
19 | copy are given as an array of io_region structures. |
20 | |
21 | struct io_region { |
22 | struct block_device *bdev; |
23 | sector_t sector; |
24 | sector_t count; |
25 | }; |
26 | |
27 | To start the copy, the user calls kcopyd_copy(), passing in the client |
28 | pointer, pointers to the source and destination io_regions, the name of a |
29 | completion callback routine, and a pointer to some context data for the copy. |
30 | |
31 | int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from, |
32 | unsigned int num_dests, struct io_region *dests, |
33 | unsigned int flags, kcopyd_notify_fn fn, void *context); |
34 | |
35 | typedef void (*kcopyd_notify_fn)(int read_err, unsigned int write_err, |
36 | void *context); |
37 | |
38 | When the copy completes, kcopyd will call the user's completion routine, |
39 | passing back the user's context pointer. It will also indicate if a read or |
40 | write error occurred during the copy. |
41 | |
42 | When a user is done with all their copy jobs, they should call |
43 | kcopyd_client_destroy() to delete the kcopyd client, which will release the |
44 | associated memory pages. |
45 | |
46 | void kcopyd_client_destroy(struct kcopyd_client *kc); |
47 | |
48 |
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Tags:
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