Commit | Line | Data |
---|---|---|
3407ef52 JB |
1 | dm-flakey |
2 | ========= | |
3 | ||
b26f5e3d MS |
4 | This target is the same as the linear target except that it exhibits |
5 | unreliable behaviour periodically. It's been found useful in simulating | |
6 | failing devices for testing purposes. | |
3407ef52 JB |
7 | |
8 | Starting from the time the table is loaded, the device is available for | |
b26f5e3d MS |
9 | <up interval> seconds, then exhibits unreliable behaviour for <down |
10 | interval> seconds, and then this cycle repeats. | |
3407ef52 | 11 | |
b26f5e3d MS |
12 | Also, consider using this in combination with the dm-delay target too, |
13 | which can delay reads and writes and/or send them to different | |
14 | underlying devices. | |
15 | ||
16 | Table parameters | |
17 | ---------------- | |
18 | <dev path> <offset> <up interval> <down interval> \ | |
19 | [<num_features> [<feature arguments>]] | |
20 | ||
21 | Mandatory parameters: | |
3407ef52 JB |
22 | <dev path>: Full pathname to the underlying block-device, or a |
23 | "major:minor" device-number. | |
24 | <offset>: Starting sector within the device. | |
25 | <up interval>: Number of seconds device is available. | |
26 | <down interval>: Number of seconds device returns errors. | |
b26f5e3d MS |
27 | |
28 | Optional feature parameters: | |
29 | If no feature parameters are present, during the periods of | |
30 | unreliability, all I/O returns errors. | |
31 | ||
32 | drop_writes: | |
33 | All write I/O is silently ignored. | |
34 | Read I/O is handled correctly. | |
a3998799 | 35 | |
0c6c987f NB |
36 | error_writes: |
37 | All write I/O is failed with an error signalled. | |
38 | Read I/O is handled correctly. | |
39 | ||
a3998799 MS |
40 | corrupt_bio_byte <Nth_byte> <direction> <value> <flags>: |
41 | During <down interval>, replace <Nth_byte> of the data of | |
42 | each matching bio with <value>. | |
43 | ||
44 | <Nth_byte>: The offset of the byte to replace. | |
45 | Counting starts at 1, to replace the first byte. | |
46 | <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes. | |
47 | 'w' is incompatible with drop_writes. | |
48 | <value>: The value (from 0-255) to write. | |
1eff9d32 | 49 | <flags>: Perform the replacement only if bio->bi_opf has all the |
a3998799 MS |
50 | selected flags set. |
51 | ||
52 | Examples: | |
53 | corrupt_bio_byte 32 r 1 0 | |
54 | - replaces the 32nd byte of READ bios with the value 1 | |
55 | ||
56 | corrupt_bio_byte 224 w 0 32 | |
57 | - replaces the 224th byte of REQ_META (=32) bios with the value 0 |