dm flakey: add corrupt_bio_byte feature

[pandora-kernel.git] / Documentation / device-mapper / dm-flakey.txt

diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
index 1b66c86..6ff5c23 100644 (file)
--- a/Documentation/device-mapper/dm-flakey.txt
+++ b/Documentation/device-mapper/dm-flakey.txt
@@ -32,3 +32,22 @@ Optional feature parameters:
   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