[dm-devel] [PATCH] dm flakey: document corrupt_bio_byte and optional feature precedence
Mike Snitzer
snitzer at redhat.com
Wed Jun 29 14:41:13 UTC 2011
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
Documentation/device-mapper/dm-flakey.txt | 15 ++++++++++++++-
1 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
index 6b40f79..6b4df49 100644
--- a/Documentation/device-mapper/dm-flakey.txt
+++ b/Documentation/device-mapper/dm-flakey.txt
@@ -27,7 +27,20 @@ Mandatory parameters:
Optional feature parameters:
If no feature parameters are present, during the periods of
- unreliability, all I/O returns errors.
+ unreliability, all I/O returns errors. Optional features may be
+ combined (e.g. corrupt_bio_byte on READ and drop_writes). Conflicting
+ features (e.g. corrupt_bio_byte on WRITE and drop_writes) are resolved
+ according to the following feature precedence (descending order):
+
+ corrupt_bio_byte <Nth byte> <bio_flags> <value>:
+ Corrupt bios that have specific bi_rw flag(s), e.g.: READ=0 or
+ REQ_WRITE=1|REQ_META=32, by writing <value> to the <Nth byte> of
+ bios that have data.
+ Examples:
+ 1) corrupt 32nd byte in READ bios with the value 1:
+ corrupt_bio_byte 32 0 1
+ 2) corrupt 224th byte in WRITE|REQ_META bios with the value 0:
+ corrupt_bio_byte 224 33 0
drop_writes:
All write I/O is silently ignored.
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