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From: Stefan Hajnoczi <stefanha@redhat.com>
To: Max Reitz <mreitz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH v2 2/4] luks: implement .bdrv_measure()
Date: Wed, 15 Jan 2020 13:41:40 +0000
Message-ID: <20200115134140.GH163546@stefanha-x1.localdomain> (raw)
In-Reply-To: <1e812068-4009-9203-c252-5922000dbbb3@redhat.com>

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On Tue, Jan 14, 2020 at 04:43:36PM +0100, Max Reitz wrote:
> On 09.01.20 12:10, Stefan Hajnoczi wrote:
> > Add qemu-img measure support in the "luks" block driver.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  block/crypto.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 82 insertions(+)
> > 
> > diff --git a/block/crypto.c b/block/crypto.c
> > index ed32202fa2..51f37bb1f6 100644
> > --- a/block/crypto.c
> > +++ b/block/crypto.c
> > @@ -548,6 +548,87 @@ static int64_t block_crypto_getlength(BlockDriverState *bs)
> 
> [...]
> 
> > +            if (ret & BDRV_BLOCK_ZERO) {
> > +                /* Skip zero regions */
> > +            } else if ((ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) ==
> > +                       (BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED)) {
> > +                /* Count clusters we've seen */
> > +                required += pnum;
> > +            }
> 
> Don’t LUKS-encrypted files allocate effectively everything because zero
> data has to be encrypted, too?
> 
> (“Effectively”, because you could zero out regions that are zero when
> encrypted, but...)
> 
> > +        }
> > +    }
> > +
> > +    /* Take into account preallocation.  Nothing special is needed for
> > +     * PREALLOC_MODE_METADATA since metadata is always counted.
> > +     */
> > +    if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) {
> > +        required = virtual_size;
> 
> Same here.  I think required should always be set to virtual_size.

Good points.  I may have inherited this from the qcow2 code, where the
L2 tables can still have unallocated/zero clusters.

I'll check if this logic makes sense outside of qcow2.

Stefan

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  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-09 11:10 [PATCH v2 0/4] luks: add qemu-img measure support Stefan Hajnoczi
2020-01-09 11:10 ` [PATCH v2 1/4] luks: extract block_crypto_calculate_payload_offset() Stefan Hajnoczi
2020-01-14 15:25   ` Max Reitz
2020-01-15 13:40     ` Stefan Hajnoczi
2020-01-15 14:35       ` Max Reitz
2020-01-09 11:10 ` [PATCH v2 2/4] luks: implement .bdrv_measure() Stefan Hajnoczi
2020-01-14 15:43   ` Max Reitz
2020-01-15 13:41     ` Stefan Hajnoczi [this message]
2020-01-09 11:10 ` [PATCH v2 3/4] qemu-img: allow qemu-img measure --object without a filename Stefan Hajnoczi
2020-01-14 15:44   ` Max Reitz
2020-01-09 11:10 ` [PATCH v2 4/4] iotests: add 282 luks qemu-img measure test Stefan Hajnoczi
2020-01-14 15:48   ` Max Reitz

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