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-dm-flakey
-=========
-
-This target is the same as the linear target except that it exhibits
-unreliable behaviour periodically. It's been found useful in simulating
-failing devices for testing purposes.
-
-Starting from the time the table is loaded, the device is available for
-<up interval> seconds, then exhibits unreliable behaviour for <down
-interval> seconds, and then this cycle repeats.
-
-Also, consider using this in combination with the dm-delay target too,
-which can delay reads and writes and/or send them to different
-underlying devices.
-
-Table parameters
-----------------
- <dev path> <offset> <up interval> <down interval> \
- [<num_features> [<feature arguments>]]
-
-Mandatory parameters:
- <dev path>: Full pathname to the underlying block-device, or a
- "major:minor" device-number.
- <offset>: Starting sector within the device.
- <up interval>: Number of seconds device is available.
- <down interval>: Number of seconds device returns errors.
-
-Optional feature parameters:
- If no feature parameters are present, during the periods of
- unreliability, all I/O returns errors.
-
- drop_writes:
- All write I/O is silently ignored.
- Read I/O is handled correctly.
-
- corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
- During <down interval>, replace <Nth_byte> of the data of
- each matching bio with <value>.
-
- <Nth_byte>: The offset of the byte to replace.
- Counting starts at 1, to replace the first byte.
- <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes.
- 'w' is incompatible with drop_writes.
- <value>: The value (from 0-255) to write.
- <flags>: Perform the replacement only if bio->bi_rw has all the
- selected flags set.
-
-Examples:
- corrupt_bio_byte 32 r 1 0
- - replaces the 32nd byte of READ bios with the value 1
-
- corrupt_bio_byte 224 w 0 32
- - replaces the 224th byte of REQ_META (=32) bios with the value 0