1 ========= 1 =========
2 dm-flakey 2 dm-flakey
3 ========= 3 =========
4 4
5 This target is the same as the linear target e 5 This target is the same as the linear target except that it exhibits
6 unreliable behaviour periodically. It's been 6 unreliable behaviour periodically. It's been found useful in simulating
7 failing devices for testing purposes. 7 failing devices for testing purposes.
8 8
9 Starting from the time the table is loaded, th 9 Starting from the time the table is loaded, the device is available for
10 <up interval> seconds, then exhibits unreliabl 10 <up interval> seconds, then exhibits unreliable behaviour for <down
11 interval> seconds, and then this cycle repeats 11 interval> seconds, and then this cycle repeats.
12 12
13 Also, consider using this in combination with 13 Also, consider using this in combination with the dm-delay target too,
14 which can delay reads and writes and/or send t 14 which can delay reads and writes and/or send them to different
15 underlying devices. 15 underlying devices.
16 16
17 Table parameters 17 Table parameters
18 ---------------- 18 ----------------
19 19
20 :: 20 ::
21 21
22 <dev path> <offset> <up interval> <down inte 22 <dev path> <offset> <up interval> <down interval> \
23 [<num_features> [<feature arguments>]] 23 [<num_features> [<feature arguments>]]
24 24
25 Mandatory parameters: 25 Mandatory parameters:
26 26
27 <dev path>: 27 <dev path>:
28 Full pathname to the underlying block- 28 Full pathname to the underlying block-device, or a
29 "major:minor" device-number. 29 "major:minor" device-number.
30 <offset>: 30 <offset>:
31 Starting sector within the device. 31 Starting sector within the device.
32 <up interval>: 32 <up interval>:
33 Number of seconds device is available. 33 Number of seconds device is available.
34 <down interval>: 34 <down interval>:
35 Number of seconds device returns error 35 Number of seconds device returns errors.
36 36
37 Optional feature parameters: 37 Optional feature parameters:
38 38
39 If no feature parameters are present, during 39 If no feature parameters are present, during the periods of
40 unreliability, all I/O returns errors. 40 unreliability, all I/O returns errors.
41 41
42 error_reads: 42 error_reads:
43 All read I/O is failed with an error s 43 All read I/O is failed with an error signalled.
44 Write I/O is handled correctly. 44 Write I/O is handled correctly.
45 45
46 drop_writes: 46 drop_writes:
47 All write I/O is silently ignored. 47 All write I/O is silently ignored.
48 Read I/O is handled correctly. 48 Read I/O is handled correctly.
49 49
50 error_writes: 50 error_writes:
51 All write I/O is failed with an error 51 All write I/O is failed with an error signalled.
52 Read I/O is handled correctly. 52 Read I/O is handled correctly.
53 53
54 corrupt_bio_byte <Nth_byte> <direction> <val 54 corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
55 During <down interval>, replace <Nth_b 55 During <down interval>, replace <Nth_byte> of the data of
56 each matching bio with <value>. 56 each matching bio with <value>.
57 57
58 <Nth_byte>: 58 <Nth_byte>:
59 The offset of the byte to replace. 59 The offset of the byte to replace.
60 Counting starts at 1, to replace the f 60 Counting starts at 1, to replace the first byte.
61 <direction>: 61 <direction>:
62 Either 'r' to corrupt reads or 'w' to 62 Either 'r' to corrupt reads or 'w' to corrupt writes.
63 'w' is incompatible with drop_writes. 63 'w' is incompatible with drop_writes.
64 <value>: 64 <value>:
65 The value (from 0-255) to write. 65 The value (from 0-255) to write.
66 <flags>: 66 <flags>:
67 Perform the replacement only if bio->b 67 Perform the replacement only if bio->bi_opf has all the
68 selected flags set. 68 selected flags set.
69 69
70 random_read_corrupt <probability> 70 random_read_corrupt <probability>
71 During <down interval>, replace random 71 During <down interval>, replace random byte in a read bio
72 with a random value. probability is an 72 with a random value. probability is an integer between
73 0 and 1000000000 meaning 0% to 100% pr 73 0 and 1000000000 meaning 0% to 100% probability of corruption.
74 74
75 random_write_corrupt <probability> 75 random_write_corrupt <probability>
76 During <down interval>, replace random 76 During <down interval>, replace random byte in a write bio
77 with a random value. probability is an 77 with a random value. probability is an integer between
78 0 and 1000000000 meaning 0% to 100% pr 78 0 and 1000000000 meaning 0% to 100% probability of corruption.
79 79
80 Examples: 80 Examples:
81 81
82 Replaces the 32nd byte of READ bios with the v 82 Replaces the 32nd byte of READ bios with the value 1::
83 83
84 corrupt_bio_byte 32 r 1 0 84 corrupt_bio_byte 32 r 1 0
85 85
86 Replaces the 224th byte of REQ_META (=32) bios 86 Replaces the 224th byte of REQ_META (=32) bios with the value 0::
87 87
88 corrupt_bio_byte 224 w 0 32 88 corrupt_bio_byte 224 w 0 32
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