Implement bdrv_amend_options for compat, size, backing_file, backing_fmt
and lazy_refcounts.
Downgrading images from compat=1.1 to compat=0.10 is achieved through
handling all incompatible flags accordingly, clearing all compatible and
autoclear flags and expanding all zero clusters.
Signed-off-by: Max Reitz <address@hidden>
---
block/qcow2-cluster.c | 165 ++++++++++++++++++++++++++++++++++++++++++
block/qcow2.c | 194 +++++++++++++++++++++++++++++++++++++++++++++++++-
block/qcow2.h | 3 +
3 files changed, 361 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index cca76d4..e0ca104 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1476,3 +1476,168 @@ fail:
return ret;
}
+
+/*
+ * Expands all zero clusters in a specific L1 table (or deallocates them, for
+ * non-backed non-pre-allocated zero clusters).
+ */
+static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
+ int l1_size)
+{
+ BDRVQcowState *s = bs->opaque;
+ bool is_active_l1 = (l1_table == s->l1_table);
+ uint64_t *l2_table;
+ int ret;
+ int i, j;
+
+ if (!is_active_l1) {
+ /* inactive L2 tables require a buffer to be stored in when loading
+ * them from disk */
+ l2_table = qemu_blockalign(bs, s->cluster_size);
+ }
+
+ for (i = 0; i < l1_size; i++) {
+ uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
+ bool l2_dirty = false;
+
+ if (!l2_offset) {
+ /* unallocated */
+ continue;
+ }
+
+ if (is_active_l1) {
+ /* get active L2 tables from cache */
+ ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
+ (void **)&l2_table);
+ } else {
+ /* load inactive L2 tables from disk */
+ ret = bdrv_read(bs->file, l2_offset / BDRV_SECTOR_SIZE,
+ (void *)l2_table, s->cluster_sectors);
+ }
+ if (ret < 0) {
+ goto fail;
+ }
+
+ for (j = 0; j < s->l2_size; j++) {
+ uint64_t l2_entry = be64_to_cpu(l2_table[j]);
+ int64_t offset;
+
+ if (qcow2_get_cluster_type(l2_entry) != QCOW2_CLUSTER_ZERO) {
+ continue;
+ }
+
+ offset = l2_entry & L2E_OFFSET_MASK;
+ if (!offset) {
+ /* not preallocated */
+ if (!bs->backing_hd) {
+ /* not backed; therefore we can simply deallocate the
+ * cluster */
+ l2_table[j] = 0;
+ l2_dirty = true;
+ continue;
+ }
+
+ offset = qcow2_alloc_clusters(bs, s->cluster_size);
+ if (offset < 0) {
+ ret = offset;
+ goto fail;
+ }
+ }
+
+ ret = bdrv_write_zeroes(bs->file, offset / BDRV_SECTOR_SIZE,
+ s->cluster_sectors);
+ if (ret < 0) {
+ qcow2_free_clusters(bs, offset, s->cluster_size,
+ QCOW2_DISCARD_ALWAYS);
+ goto fail;
+ }
+
+ l2_table[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED);
+ l2_dirty = true;
+ }
+
+ if (is_active_l1) {
+ if (l2_dirty) {
+ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
+ qcow2_cache_depends_on_flush(s->l2_table_cache);
+ }
+ ret = qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
+ if (ret < 0) {
+ l2_table = NULL;
+ goto fail;
+ }
+ } else {
+ if (l2_dirty) {
+ ret = bdrv_write(bs->file, l2_offset / BDRV_SECTOR_SIZE,
+ (void *)l2_table, s->cluster_sectors);
+ if (ret < 0) {
+ goto fail;
+ }
+ }
+ }
+ }
+
+ ret = 0;
+
+fail:
+ if (l2_table) {
+ if (!is_active_l1) {
+ qemu_vfree(l2_table);
+ } else {
+ if (ret < 0) {
+ qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
+ } else {
+ ret = qcow2_cache_put(bs, s->l2_table_cache,
+ (void **)&l2_table);
+ }
+ }
+ }
+ return ret;
+}
+
+/*
+ * For backed images, expands all zero clusters on the image. For non-backed
+ * images, deallocates all non-pre-allocated zero clusters (and claims the
+ * allocation for pre-allocated ones). This is important for downgrading to a
+ * qcow2 version which doesn't yet support metadata zero clusters.
+ */
+int qcow2_expand_zero_clusters(BlockDriverState *bs)
+{
+ BDRVQcowState *s = bs->opaque;
+ uint64_t *l1_table = NULL;
+ int ret;
+ int i, j;
+
+ ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size);
+ if (ret < 0) {
+ goto fail;
+ }
+
+ for (i = 0; i < s->nb_snapshots; i++) {
+ int l1_sectors = (s->snapshots[i].l1_size * sizeof(uint64_t) +
+ BDRV_SECTOR_SIZE - 1) / BDRV_SECTOR_SIZE;
+
+ l1_table = g_realloc(l1_table, l1_sectors * BDRV_SECTOR_SIZE);
+
+ ret = bdrv_read(bs->file, s->snapshots[i].l1_table_offset /
+ BDRV_SECTOR_SIZE, (void *)l1_table, l1_sectors);
+ if (ret < 0) {
+ goto fail;
+ }
+
+ for (j = 0; j < s->snapshots[i].l1_size; j++) {
+ be64_to_cpus(&l1_table[j]);
+ }
+
+ ret = expand_zero_clusters_in_l1(bs, l1_table,
s->snapshots[i].l1_size);
+ if (ret < 0) {
+ goto fail;
+ }
+ }
+
+ ret = 0;
+
+fail:
+ g_free(l1_table);
+ return ret;
+}
diff --git a/block/qcow2.c b/block/qcow2.c
index 78097e5..a8eaf45 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -409,6 +409,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options,
int flags)
ret = -ENOTSUP;
goto fail;
}
+ s->refcount_order = header.refcount_order;
if (header.cluster_bits < MIN_CLUSTER_BITS ||
header.cluster_bits > MAX_CLUSTER_BITS) {
@@ -1076,7 +1077,7 @@ int qcow2_update_header(BlockDriverState *bs)
.incompatible_features = cpu_to_be64(s->incompatible_features),
.compatible_features = cpu_to_be64(s->compatible_features),
.autoclear_features = cpu_to_be64(s->autoclear_features),
- .refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT),
+ .refcount_order = cpu_to_be32(s->refcount_order),
.header_length = cpu_to_be32(header_length),
};
@@ -1735,6 +1736,196 @@ static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
return ret;
}
+/*
+ * Downgrades an image's version. To achieve this, any incompatible features
+ * have to be removed.
+ */
+static int qcow2_downgrade(BlockDriverState *bs, int target_version)
+{
+ BDRVQcowState *s = bs->opaque;
+ int current_version = s->qcow_version;
+ int ret;
+
+ if (target_version == current_version) {
+ return 0;
+ } else if (target_version > current_version) {
+ return -EINVAL;
+ } else if (target_version != 2) {
+ return -EINVAL;
+ }
+
+ if (s->refcount_order != 4) {
+ /* we would have to convert the image to a refcount_order == 4 image
+ * here; however, since qemu (at the time of writing this) does not
+ * support anything different than 4 anyway, there is no point in doing
+ * so right now; however, we should error out (if qemu supports this in
+ * the future and this code has not been adapted) */
+ error_report("qcow2_downgrade: Image refcount orders other than 4 are"
+ "currently not supported.");
+ return -ENOTSUP;
+ }
+
+ /* clear incompatible features */
+ if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) {
+ ret = qcow2_mark_clean(bs);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ if (s->incompatible_features) {
+ return -ENOTSUP;
+ }
+
+ /* since we can ignore compatible features, we can set them to 0 as well */
+ s->compatible_features = 0;
+ /* if lazy refcounts have been used, they have already been fixed through
+ * clearing the dirty flag */
+
+ /* clearing autoclear features is trivial */
+ s->autoclear_features = 0;
+
+ ret = qcow2_expand_zero_clusters(bs);
+ if (ret < 0) {
+ return ret;
+ }
+
+ s->qcow_version = target_version;
+ ret = qcow2_update_header(bs);
+ if (ret < 0) {
+ s->qcow_version = current_version;
+ return ret;
+ }
+ return 0;
+}
+
+static int qcow2_amend_options(BlockDriverState *bs,
+ QEMUOptionParameter *options)
+{
+ BDRVQcowState *s = bs->opaque;
+ int old_version = s->qcow_version, new_version = old_version;
+ uint64_t new_size = 0;
+ const char *backing_file = NULL, *backing_format = NULL;
+ bool lazy_refcounts = s->use_lazy_refcounts;
+ int ret;
+ int i;
+
+ for (i = 0; options[i].name; i++)
+ {
+ if (!strcmp(options[i].name, "compat")) {
+ if (!options[i].value.s) {
+ /* preserve default */
+ } else if (!strcmp(options[i].value.s, "0.10")) {
+ new_version = 2;
+ } else if (!strcmp(options[i].value.s, "1.1")) {
+ new_version = 3;
+ } else {
+ fprintf(stderr, "Unknown compatibility level %s.\n",
+ options[i].value.s);
+ return -EINVAL;
+ }
+ } else if (!strcmp(options[i].name, "preallocation")) {
+ if (options[i].assigned) {