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1 | dm-flakey |
2 | ========= |
3 | |
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. |
7 | |
8 | Starting from the time the table is loaded, the device is available for |
9 | <up interval> seconds, then exhibits unreliable behaviour for <down |
10 | interval> seconds, and then this cycle repeats. |
11 | |
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: |
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. |
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. |
35 | |
36 | corrupt_bio_byte <Nth_byte> <direction> <value> <flags>: |
37 | During <down interval>, replace <Nth_byte> of the data of |
38 | each matching bio with <value>. |
39 | |
40 | <Nth_byte>: The offset of the byte to replace. |
41 | Counting starts at 1, to replace the first byte. |
42 | <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes. |
43 | 'w' is incompatible with drop_writes. |
44 | <value>: The value (from 0-255) to write. |
45 | <flags>: Perform the replacement only if bio->bi_rw has all the |
46 | selected flags set. |
47 | |
48 | Examples: |
49 | corrupt_bio_byte 32 r 1 0 |
50 | - replaces the 32nd byte of READ bios with the value 1 |
51 | |
52 | corrupt_bio_byte 224 w 0 32 |
53 | - replaces the 224th byte of REQ_META (=32) bios with the value 0 |
54 |
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Tags:
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