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Subject: Re: [PATCH v2 1/3] xen: xenbus_dev_frontend: Fix XS_TRANSACTION_END
 handling
To:     Simon Gaiser <simon@invisiblethingslab.com>,
        xen-devel@lists.xenproject.org
Cc:     stable@vger.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        linux-kernel@vger.kernel.org
References: <20180315024322.27429-1-simon@invisiblethingslab.com>
From:   Juergen Gross <jgross@suse.com>
Message-ID: <3e626882-eac6-12db-9f5e-a75994bbdf2d@suse.com>
Date:   Thu, 15 Mar 2018 11:33:36 +0100
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On 15/03/18 03:43, Simon Gaiser wrote:
> Commit fd8aa9095a95 ("xen: optimize xenbus driver for multiple
> concurrent xenstore accesses") made a subtle change to the semantic of
> xenbus_dev_request_and_reply() and xenbus_transaction_end().
> 
> Before on an error response to XS_TRANSACTION_END
> xenbus_dev_request_and_reply() would not decrement the active
> transaction counter. But xenbus_transaction_end() has always counted the
> transaction as finished regardless of the response.
> 
> The new behavior is that xenbus_dev_request_and_reply() and
> xenbus_transaction_end() will always count the transaction as finished
> regardless the response code (handled in xs_request_exit()).
> 
> But xenbus_dev_frontend tries to end a transaction on closing of the
> device if the XS_TRANSACTION_END failed before. Trying to close the
> transaction twice corrupts the reference count. So fix this by also
> considering a transaction closed if we have sent XS_TRANSACTION_END once
> regardless of the return code.
> 
> Cc: <stable@vger.kernel.org> # 4.11
> Fixes: fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
> Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen