Re: [Qemu-devel] [PATCH v12 16/17] blkdebug: fix "once" rule

[Max Reitz <mreitz@redhat.com>]

On 2015-02-09 at 20:35, John Snow wrote:
> Background:
>    The blkdebug scripts are currently engineered so that when a debug
> event occurs, a prefilter browses a master list of parsed rules for a
> certain event and adds them to an "active list" of rules to be used for
> the forthcoming action, provided the events and state numbers match.
>
>    Then, once the request is received, the last active rule is used to
> inject an error if certain parameters match.
>
>    This active list is cleared every time the prefilter injects a new
> rule for the first time during a debug event.
>
>    The "once" rule currently causes the error injection, if it is
> triggered, to only clear the active list. This is insufficient for
> preventing future injections of the same rule.
>
> Remedy:
>    This patch /deletes/ the rule from the list that the prefilter
> browses, so it is gone for good. In V2, we remove only the rule of
> interest from the active list instead of allowing the "once" rule to
> clear the entire list of active rules.
>
> Impact:
>    This affects iotests 026. Several ENOSPC tests that used "once" can
> be seen to have output that shows multiple failure messages. After
> this patch, the error messages tend to be smaller and less severe, but
> the injection can still be seen to be working. I have patched the
> expected output to expect the smaller error messages.
>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>   block/blkdebug.c           |  6 ++++--
>   tests/qemu-iotests/026.out | 24 ++++--------------------
>   2 files changed, 8 insertions(+), 22 deletions(-)

Well, I think this shouldn't be part of this series, but you can find my 
R-b here: 
http://lists.nongnu.org/archive/html/qemu-devel/2015-02/msg01209.html

Max