linux-kernel - Re: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance discard support with secure erasing support.

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Message-ID: <20111020034631.GC2401@phenom.dumpdata.com>
Date:	Wed, 19 Oct 2011 23:46:31 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Li Dongyang <lidongyang@...ell.com>
Cc:	Jan Beulich <JBeulich@...e.com>,
	Dong Yang Li <lidongyang@...e.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hch@...radead.org" <hch@...radead.org>
Subject: Re: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance discard
 support with secure erasing support.

On Thu, Oct 20, 2011 at 11:17:14AM +0800, Li Dongyang wrote:
> I think we also should mark the vbd has discard_secure if we are
> usingthe file backend,as if we punch a hole in the image, those blocks
> are freed tofilesystem and hardly to getthem back, or maybe write
> zeros to the range before we punch the hole is better?

You would have to write zeros to that range (or perhaps random values)
to emulate the secure delete. If you have a patch for that I would be interested
in seeing it.

Hmm, which reminds me - I should repost this patch series.

> On Mon, Oct 17, 2011 at 9:23 PM, Jan Beulich <JBeulich@...e.com> wrote:
> >>>> On 11.10.11 at 22:57, Konrad Rzeszutek Wilk <konrad.wilk@...cle.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);
> >>  }
> >>
> >
> >
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xensource.com
> http://lists.xensource.com/xen-devel
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