Re: [Qemu-devel] [PATCH 03/21] qcow2: Use 64 bits for refcount values

[Max Reitz]

On 2014-11-10 at 21:59, Eric Blake wrote:
> On 11/10/2014 06:45 AM, Max Reitz wrote:
> > Refcounts may have a width of up to 64 bit, so qemu should use the same
> s/bit/bits/

See my reply to your review on patch 2. I keep swapping knowing which to 
use - now I know, thanks!

> > width to represent refcount values internally.
> >
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >   block/qcow2-cluster.c  |  9 ++++++---
> >   block/qcow2-refcount.c | 37 ++++++++++++++++++++-----------------
> >   block/qcow2.h          |  7 ++++---
> >   3 files changed, 30 insertions(+), 23 deletions(-)
> >
> > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> > index df0b2c9..ab43902 100644
> > --- a/block/qcow2-cluster.c
> > +++ b/block/qcow2-cluster.c
> > @@ -1640,7 +1640,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState 
> > *bs, uint64_t *l1_table,
> >       for (i = 0; i < l1_size; i++) {
> >           uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
> >           bool l2_dirty = false;
> > -        int l2_refcount;
> > +        int64_t l2_refcount;
> You may want to mention in the commit message that you choose a signed
> type to allow negative for errors, and therefore we really allow only up
> to 63 useful bits.  Or even mention that this is  okay because no one
> can feasibly generate an image with more than 2^63 refs to the same
> cluster (there isn't that much storage or time to do such a task in our
> lifetime...)

Will do.

Max

> Reviewed-by: Eric Blake <address@hidden>