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