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-   -   dm flakey: document corrupt_bio_byte and optional feature precedence (http://www.linux-archive.org/device-mapper-development/546063-dm-flakey-document-corrupt_bio_byte-optional-feature-precedence.html)

Mike Snitzer 06-29-2011 02:41 PM

dm flakey: document corrupt_bio_byte and optional feature precedence
 
Signed-off-by: Mike Snitzer <snitzer@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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Mike Snitzer 06-29-2011 02:52 PM

dm flakey: document corrupt_bio_byte and optional feature precedence
 
On Wed, Jun 29 2011 at 10:41am -0400,
Mike Snitzer <snitzer@redhat.com> wrote:

> Signed-off-by: Mike Snitzer <snitzer@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.

Gah, we should also add:

<value> may be 0 or 1. Bios that don't match <bio_flags> fall through
to the other optional feature(s) or the default of returning I/O error.

> + 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.
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel

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