Re: [Qemu-devel] [PATCH 6/8] qemu-img: use bdrv_write_zeroes to write zeroes

[Paolo Bonzini <pbonzini@redhat.com>]

Il 24/06/2013 18:17, Peter Lieven ha scritto:
> Am 24.06.2013 16:33, schrieb Paolo Bonzini:
>> Il 22/06/2013 22:58, Peter Lieven ha scritto:
>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>> ---
>>>  qemu-img.c |   10 +++++++---
>>>  1 file changed, 7 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/qemu-img.c b/qemu-img.c
>>> index 809b4f1..5aa53ab 100644
>>> --- a/qemu-img.c
>>> +++ b/qemu-img.c
>>> @@ -1513,9 +1513,13 @@ static int img_convert(int argc, char **argv)
>>>                     If the output is to a host device, we also write out
>>>                     sectors that are entirely 0, since whatever data was
>>>                     already there is garbage, not 0s. */
>>> -                if (!has_zero_init || out_baseimg ||
>>> -                    is_allocated_sectors_min(buf1, n, &n1, min_sparse)) {
>>> -                    ret = bdrv_write(out_bs, sector_num, buf1, n1);
>>> +                int allocated = is_allocated_sectors_min(buf1, n, &n1, min_sparse);
>>> +                if (!has_zero_init || out_baseimg || allocated) {
>>> +                    if (allocated || out_baseimg) {
>>> +                        ret = bdrv_write(out_bs, sector_num, buf1, n1);
>>> +                    } else {
>>> +                        ret = bdrv_write_zeroes(out_bs, sector_num, n1);
>> I think it should still do the write only if !has_zero_init.
> With this I am still in trouble with iSCSI, but Kevin pointed out another
> possible solution for the allocating everything problem.
> 
> a) let iscsi_create discard the whole device if lbpz && lbprz
> b) return 1 for has_zero_init if lbprz.
> 
> What do you think?

Fine by me (but the discard may take a looong time! :)).

Paolo