Image file compression works at cluster granularity. It is not possible
to compress less than a cluster of data at a time.
Print an error when attempting qemu-img convert -c with an input file
that is not a multiple of the cluster size.
I considered automatically adjusting the output file size but think it's
better to be explicit. This avoids confusion when users notice that
image file size changed after conversion.
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
qemu-img.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/qemu-img.c b/qemu-img.c
index 31627b0..2273851 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1370,6 +1370,13 @@ static int img_convert(int argc, char **argv)
goto out;
}
cluster_sectors = cluster_size >> 9;
+ if (total_sectors % cluster_sectors) {
+ error_report("compression requires that input file size is a "
+ "multiple of %d bytes",
+ cluster_size);
+ ret = -1;
+ goto out;
+ }
sector_num = 0;
nb_sectors = total_sectors;
--
1.8.1.4
