If the target has_zero_init = 0, but supports efficiently
writing zeroes by unmapping we call bdrv_zeroize to
avoid fully allocating the target. Ihis currently
is designed especially for iscsi.
Reviewed-by: Eric Blake <ebl...@redhat.com>
Signed-off-by: Peter Lieven <p...@kamp.de>
---
qemu-img.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/qemu-img.c b/qemu-img.c
index c6eff15..2a41942 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1353,7 +1353,7 @@ static int img_convert(int argc, char **argv)
}
}
- flags = BDRV_O_RDWR;
+ flags = min_sparse ? (BDRV_O_RDWR | BDRV_O_UNMAP) : BDRV_O_RDWR;
ret = bdrv_parse_cache_flags(cache, &flags);
if (ret < 0) {
error_report("Invalid cache option: %s", cache);
@@ -1469,6 +1469,14 @@ static int img_convert(int argc, char **argv)
} else {
int has_zero_init = min_sparse ? bdrv_has_zero_init(out_bs) : 0;
+ if (!has_zero_init && bdrv_has_discard_write_zeroes(out_bs)) {
+ ret = bdrv_zeroize(out_bs, BDRV_REQ_MAY_UNMAP);
+ if (ret < 0) {
+ goto out;
+ }
+ has_zero_init = 1;
+ }
+
sector_num = 0; // total number of sectors converted so far
nb_sectors = total_sectors - sector_num;
if (nb_sectors != 0) {
--
1.7.9.5
