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Message-ID: <da824cf30803030933j5647b0d4k61f6d110ff9f29bb@mail.gmail.com>
Date: Mon, 3 Mar 2008 09:33:15 -0800
From: "Grant Grundler" <grundler@google.com>
To: "Hannes Reinecke" <hare@suse.de>
Subject: Re: [RFC PATCH 1/3] block: add rq->complete_io hook for request stacking
Cc: "Kiyoshi Ueda" <k-ueda@ct.jp.nec.com>, jens.axboe@oracle.com,
       linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
       dm-devel@redhat.com, j-nomura@ce.jp.nec.com
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On Mon, Mar 3, 2008 at 8:24 AM, Hannes Reinecke <hare@suse.de> wrote:

>  I would rather have rq->complete_io() to be pointing to blk_end_io in the
>  default case, this way rq->complete_io() would always be valid and we
>  would be saving us the if() clause.

This is a good idea. But...

...
>  So when using my proposal this would just become:
>
>  {
>     BUG_ON(!rq->complete_io);
>
>     return rq->complete_io(rq, error, nr_bytes, 0, NULL);
>  }

This "BUG_ON" is also an "if()" clause except
it will panic. The box will panic if the function
pointer is a null pointer and it won't be hard to
sort out why. I suggest omitting the BUG_ON.

thanks,
grant
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