Re: [OSSTEST PATCH 4/9] mg-schema-test-database: Borrow shares properly

From: Ian Campbell <ian.campbell@citrix.com>
To: Ian Jackson <ian.jackson@eu.citrix.com>, xen-devel@lists.xenproject.org
Subject: Re: [OSSTEST PATCH 4/9] mg-schema-test-database: Borrow shares properly
Date: Thu, 17 Dec 2015 17:26:20 +0000	[thread overview]
Message-ID: <1450373180.4053.143.camel@citrix.com> (raw)
In-Reply-To: <1450371968-27997-4-git-send-email-ian.jackson@eu.citrix.com>

On Thu, 2015-12-17 at 17:06 +0000, Ian Jackson wrote:
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> ---
>  mg-schema-test-database |   14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/mg-schema-test-database b/mg-schema-test-database
> index a4cb732..4e0ee68 100755
> --- a/mg-schema-test-database
> +++ b/mg-schema-test-database
> @@ -448,12 +448,22 @@ END
>  	done
>  
>  	# As we copy, we note everything we're not borrowing as
> -	# belonging to the parent db.
> +	# belonging to the parent db.  We borrow shares of a shared
> +	# resource.  If we borrow only some rather than all of the
> +	# shares, neither DB will be able to unshare it.

This is what actually happens, rather than this comment explaining a thing
we are avoiding, right?

I ask because although the text (and the use of "properly" in the subject)
seems pretty clear it's the former I was surprised to find this code was
borrowing partial shares and therefore setting up such a situation. Given
the caveat below would it not be better to just never allow this? I suppose
that given the list of tasks to borrow came from the user this might be
considered a "keep both pieces" situation.

> +
> +	# In principle it might be possible to actually use different
> +	# shares of the same resource with different dbs.  However the
> +	# `sharetype' contains the osstest revision, which prevents
> +	# sharing between test and real versions of osstest code.
> +
>  	cat >>$t.import <<END
>  		$(make_xdbref_task $maindbname 'not borrowed' '' PARENT)
>  		UPDATE resources
>  			SET owntaskid = $(taskid xdbref $maindbname)
> -			WHERE owntaskid != $(borrowtaskid $task);
> +			WHERE owntaskid != $(borrowtaskid $task)
> +			  AND owntaskid != $(taskid magic shared)
> +			  AND owntaskid != $(taskid magic preparing);
>  		COMMIT;
>  END
>  

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