Now after shrinking the image, at the end of the image file, there might be a
tail that probably will never be used. So we can find the last used cluster and
cut the tail.
Signed-off-by: Pavel Butsykin <address@hidden>
Reviewed-by: John Snow <address@hidden>
---
block/qcow2-refcount.c | 22 ++++++++++++++++++++++
block/qcow2.c | 23 +++++++++++++++++++++++
block/qcow2.h | 1 +
3 files changed, 46 insertions(+)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 88d5a3f1ad..aa3fd6cf17 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -3181,3 +3181,25 @@ out:
g_free(reftable_tmp);
return ret;
}
+
+int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size)
+{
+ BDRVQcow2State *s = bs->opaque;
+ int64_t i;
+
+ for (i = size_to_clusters(s, size) - 1; i >= 0; i--) {
+ uint64_t refcount;
+ int ret = qcow2_get_refcount(bs, i, &refcount);
+ if (ret < 0) {
+ fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
+ i, strerror(-ret));
+ return ret;
+ }
+ if (refcount > 0) {
+ return i;
+ }
+ }
+ qcow2_signal_corruption(bs, true, -1, -1,
+ "There are no references in the refcount table.");
+ return -EIO;
+}
diff --git a/block/qcow2.c b/block/qcow2.c
index 8a4311d338..f08c69ccd9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t
offset,
new_l1_size = size_to_l1(s, offset);
if (offset < old_length) {
+ int64_t last_cluster, old_file_size;
if (prealloc != PREALLOC_MODE_OFF) {
error_setg(errp,
"Preallocation can't be used for shrinking an image");
@@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t
offset,
"Failed to discard unused refblocks");
return ret;
}
+
+ old_file_size = bdrv_getlength(bs->file->bs);
+ if (old_file_size < 0) {
+ error_setg_errno(errp, -old_file_size,
+ "Failed to inquire current file length");
+ return old_file_size;
+ }
+ last_cluster = qcow2_get_last_cluster(bs, old_file_size);
+ if (last_cluster < 0) {
+ error_setg_errno(errp, -last_cluster,
+ "Failed to find the last cluster");
+ return last_cluster;
+ }
+ if ((last_cluster + 1) * s->cluster_size < old_file_size) {
+ ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size,
+ PREALLOC_MODE_OFF, NULL);
+ if (ret < 0) {
+ warn_report("Failed to truncate the tail of the image: "
+ "ret = %d", ret);