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block: make bdrv_has_zero_init return false for copy-on-write-images 

This helps implementing is_allocated on top of get_block_status.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-09-04 19:00:27 +02:00 committed by Stefan Hajnoczi
parent e4a86f88cc
commit 11212d8fa0
2 changed files with 6 additions and 8 deletions
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5
block.c
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@ -3031,6 +3031,11 @@ int bdrv_has_zero_init(BlockDriverState *bs)
{
assert(bs->drv);
/* If BS is a copy on write image, it is initialized to
the contents of the base image, which may not be zeroes. */
if (bs->backing_hd) {
return 0;
}
if (bs->drv->bdrv_has_zero_init) {
return bs->drv->bdrv_has_zero_init(bs);
}

9
qemu-img.c
View File

@ -1537,14 +1537,7 @@ static int img_convert(int argc, char **argv)
should add a specific call to have the info to go faster */
buf1 = buf;
while (n > 0) {
/* If the output image is being created as a copy on write image,
copy all sectors even the ones containing only NUL bytes,
because they may differ from the sectors in the base image.
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 ||
if (!has_zero_init ||
is_allocated_sectors_min(buf1, n, &n1, min_sparse)) {
ret = bdrv_write(out_bs, sector_num, buf1, n1);
if (ret < 0) {