Re: [Xen-devel] tapdisk in debian 3.11 kernel

[James Harper <james.harper@xxxxxxxxxxxxxxxx>]

> 
> I can't get tapdisk to run after upgrading to 3.11 (wheezy-backports). strace
> tells me it is failing on the call to io_setup with EINVAL.
> 
> The man page for io_setup tells me that ctx_idp parameter should be
> initialised to 0, and EINVAL means ctx_idp is not initialised. Looking at the
> code for tapdisk, it appears to initialise ctx_idp to 1, with a comment:
> 
> /*
>  * We used a kernel patch to return an fd associated with the AIO context
>  * so that we can concurrently poll on synchronous and async descriptors.
>  * This is signalled by passing 1 as the io context to io_setup.
>  */
> #define REQUEST_ASYNC_FD ((io_context_t)1)
> 
> And if I create a basic test program, I can see that calling it with param 1 
> it
> does return EINVAL.
> 
> What is this patch the comment refers to? It was working under Debian 3.2.x
> 

I got it working by initialising ctx_idp to 0. I believe it uses eventfd now 
anyway and the patch is no longer required.

James

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