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-rw-r--r--block/qcow2.c46
-rw-r--r--block/qcow2.h6
2 files changed, 48 insertions, 4 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 4fa3ff99d2..21ed6f8753 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -140,7 +140,7 @@ static int qcow_read_extensions(BlockDriverState *bs, uint64_t start_offset,
static int qcow_open(BlockDriverState *bs, int flags)
{
BDRVQcowState *s = bs->opaque;
- int len, i, shift;
+ int len, i;
QCowHeader header;
uint64_t ext_end;
@@ -188,8 +188,7 @@ static int qcow_open(BlockDriverState *bs, int flags)
/* read the level 1 table */
s->l1_size = header.l1_size;
- shift = s->cluster_bits + s->l2_bits;
- s->l1_vm_state_index = (header.size + (1LL << shift) - 1) >> shift;
+ s->l1_vm_state_index = size_to_l1(s, header.size);
/* the L1 table must contain at least enough entries to put
header.size bytes */
if (s->l1_size < s->l1_vm_state_index)
@@ -851,6 +850,43 @@ static int qcow_make_empty(BlockDriverState *bs)
return 0;
}
+static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
+{
+ BDRVQcowState *s = bs->opaque;
+ int ret, new_l1_size;
+
+ if (offset & 511) {
+ return -EINVAL;
+ }
+
+ /* cannot proceed if image has snapshots */
+ if (s->nb_snapshots) {
+ return -ENOTSUP;
+ }
+
+ /* shrinking is currently not supported */
+ if (offset < bs->total_sectors * 512) {
+ return -ENOTSUP;
+ }
+
+ new_l1_size = size_to_l1(s, offset);
+ ret = qcow2_grow_l1_table(bs, new_l1_size);
+ if (ret < 0) {
+ return ret;
+ }
+
+ /* write updated header.size */
+ offset = cpu_to_be64(offset);
+ ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, size),
+ &offset, sizeof(uint64_t));
+ if (ret < 0) {
+ return ret;
+ }
+
+ s->l1_vm_state_index = new_l1_size;
+ return 0;
+}
+
/* XXX: put compressed sectors first, then all the cluster aligned
tables to avoid losing bytes in alignment */
static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num,
@@ -1050,7 +1086,9 @@ static BlockDriver bdrv_qcow2 = {
.bdrv_aio_readv = qcow_aio_readv,
.bdrv_aio_writev = qcow_aio_writev,
.bdrv_aio_flush = qcow_aio_flush,
- .bdrv_write_compressed = qcow_write_compressed,
+
+ .bdrv_truncate = qcow2_truncate,
+ .bdrv_write_compressed = qcow_write_compressed,
.bdrv_snapshot_create = qcow2_snapshot_create,
.bdrv_snapshot_goto = qcow2_snapshot_goto,
diff --git a/block/qcow2.h b/block/qcow2.h
index 5bd08db11c..01053b79d9 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -150,6 +150,12 @@ static inline int size_to_clusters(BDRVQcowState *s, int64_t size)
return (size + (s->cluster_size - 1)) >> s->cluster_bits;
}
+static inline int size_to_l1(BDRVQcowState *s, int64_t size)
+{
+ int shift = s->cluster_bits + s->l2_bits;
+ return (size + (1ULL << shift) - 1) >> shift;
+}
+
static inline int64_t align_offset(int64_t offset, int n)
{
offset = (offset + n - 1) & ~(n - 1);