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1=========2dm-flakey3=========4 5This target is the same as the linear target except that it exhibits6unreliable behaviour periodically. It's been found useful in simulating7failing devices for testing purposes.8 9Starting from the time the table is loaded, the device is available for10<up interval> seconds, then exhibits unreliable behaviour for <down11interval> 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 different15underlying devices.16 17Table parameters18----------------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 a29 "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 of40 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 of56 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 the68 selected flags set.69 70 random_read_corrupt <probability>71 During <down interval>, replace random byte in a read bio72 with a random value. probability is an integer between73 0 and 1000000000 meaning 0% to 100% probability of corruption.74 75 random_write_corrupt <probability>76 During <down interval>, replace random byte in a write bio77 with a random value. probability is an integer between78 0 and 1000000000 meaning 0% to 100% probability of corruption.79 80Examples:81 82Replaces the 32nd byte of READ bios with the value 1::83 84 corrupt_bio_byte 32 r 1 085 86Replaces the 224th byte of REQ_META (=32) bios with the value 0::87 88 corrupt_bio_byte 224 w 0 3289