Re: [Qemu-devel] [PATCH v3] blkdebug: fix "once" rule

[Max Reitz <mreitz@redhat.com>]

On 2015-02-06 at 16:26, 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>
> ---
>
> V3:
>    - Fix interaction of "immediately" and "once" rule
>    - Remembered that my patch sending script does not work well with
>      single patches and moved the version history below the commit bump
>
> V2:
>    - Remove only the offending "once" rule from the active list instead
>      of clearing the entire active list.
>
>   block/blkdebug.c           |  6 ++++--
>   tests/qemu-iotests/026.out | 24 ++++--------------------
>   2 files changed, 8 insertions(+), 22 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>