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-rw-r--r--Documentation/device-mapper/dm-flakey.txt19
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
index 1b66c868ee7e..6ff5c2327227 100644
--- a/Documentation/device-mapper/dm-flakey.txt
+++ b/Documentation/device-mapper/dm-flakey.txt
@@ -32,3 +32,22 @@ Optional feature parameters:
32 drop_writes: 32 drop_writes:
33 All write I/O is silently ignored. 33 All write I/O is silently ignored.
34 Read I/O is handled correctly. 34 Read I/O is handled correctly.
35
36 corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
37 During <down interval>, replace <Nth_byte> of the data of
38 each matching bio with <value>.
39
40 <Nth_byte>: The offset of the byte to replace.
41 Counting starts at 1, to replace the first byte.
42 <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes.
43 'w' is incompatible with drop_writes.
44 <value>: The value (from 0-255) to write.
45 <flags>: Perform the replacement only if bio->bi_rw has all the
46 selected flags set.
47
48Examples:
49 corrupt_bio_byte 32 r 1 0
50 - replaces the 32nd byte of READ bios with the value 1
51
52 corrupt_bio_byte 224 w 0 32
53 - replaces the 224th byte of REQ_META (=32) bios with the value 0