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Date: Mon, 17 Oct 2011 14:23:01 +0100
From: "Jan Beulich" <JBeulich@suse.com>
To: "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>
Cc: "Ian Campbell" <Ian.Campbell@citrix.com>,
        "hch@infradead.org" <hch@infradead.org>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
        "Dong Yang Li" <lidongyang@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance
	 discard support with secure erasing support.
References: <1318260494-27985-1-git-send-email-konrad.wilk@oracle.com>
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 <1318263187.21903.464.camel@zakaz.uk.xensource.com>
 <20111010164250.GG28646@phenom.oracle.com>
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>>> On 11.10.11 at 22:57, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
>...
> @@ -705,7 +711,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  static void blkif_completion(struct blk_shadow *s)
>  {
>  	int i;

This function gets called for all types of requests, and hence must filter
discard ones now that what would be nr_segments can be non-zero,
e.g.

	if (s->req.operation == BLKIF_OP_DISCARD)
		return;

Jan

> -	for (i = 0; i < s->req.nr_segments; i++)
> +	for (i = 0; i < s->req.u1.nr_segments; i++)
>  		gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
>  }
>