tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1=========
2dm-flakey
3=========
4
5This target is the same as the linear target except that it exhibits
6unreliable behaviour periodically. It's been found useful in simulating
7failing devices for testing purposes.
8
9Starting from the time the table is loaded, the device is available for
10<up interval> seconds, then exhibits unreliable behaviour for <down
11interval> seconds, and then this cycle repeats.
12
13Also, consider using this in combination with the dm-delay target too,
14which can delay reads and writes and/or send them to different
15underlying devices.
16
17Table parameters
18----------------
19
20::
21
22 <dev path> <offset> <up interval> <down interval> \
23 [<num_features> [<feature arguments>]]
24
25Mandatory parameters:
26
27 <dev path>:
28 Full pathname to the underlying block-device, or a
29 "major:minor" device-number.
30 <offset>:
31 Starting sector within the device.
32 <up interval>:
33 Number of seconds device is available.
34 <down interval>:
35 Number of seconds device returns errors.
36
37Optional feature parameters:
38
39 If no feature parameters are present, during the periods of
40 unreliability, all I/O returns errors.
41
42 error_reads:
43 All read I/O is failed with an error signalled.
44 Write I/O is handled correctly.
45
46 drop_writes:
47 All write I/O is silently ignored.
48 Read I/O is handled correctly.
49
50 error_writes:
51 All write I/O is failed with an error signalled.
52 Read I/O is handled correctly.
53
54 corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
55 During <down interval>, replace <Nth_byte> of the data of
56 each matching bio with <value>.
57
58 <Nth_byte>:
59 The offset of the byte to replace.
60 Counting starts at 1, to replace the first byte.
61 <direction>:
62 Either 'r' to corrupt reads or 'w' to corrupt writes.
63 'w' is incompatible with drop_writes.
64 <value>:
65 The value (from 0-255) to write.
66 <flags>:
67 Perform the replacement only if bio->bi_opf has all the
68 selected flags set.
69
70Examples:
71
72Replaces the 32nd byte of READ bios with the value 1::
73
74 corrupt_bio_byte 32 r 1 0
75
76Replaces the 224th byte of REQ_META (=32) bios with the value 0::
77
78 corrupt_bio_byte 224 w 0 32