qcow2-cluster: Expand zero clusters
Add functionality for expanding zero clusters. This is necessary for downgrading the image version to one without zero cluster support. For non-backed images, this function may also just discard zero clusters instead of truly expanding them. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz
Kevin Wolf
parent
e7108feaac
commit
32b6444d23
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@ -1497,3 +1497,236 @@ fail:
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return ret;
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}
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/*
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* Expands all zero clusters in a specific L1 table (or deallocates them, for
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* non-backed non-pre-allocated zero clusters).
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*
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* expanded_clusters is a bitmap where every bit corresponds to one cluster in
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* the image file; a bit gets set if the corresponding cluster has been used for
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* zero expansion (i.e., has been filled with zeroes and is referenced from an
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* L2 table). nb_clusters contains the total cluster count of the image file,
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* i.e., the number of bits in expanded_clusters.
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*/
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static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
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int l1_size, uint8_t *expanded_clusters,
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uint64_t nb_clusters)
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{
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BDRVQcowState *s = bs->opaque;
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bool is_active_l1 = (l1_table == s->l1_table);
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uint64_t *l2_table = NULL;
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int ret;
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int i, j;
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if (!is_active_l1) {
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/* inactive L2 tables require a buffer to be stored in when loading
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* them from disk */
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l2_table = qemu_blockalign(bs, s->cluster_size);
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}
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for (i = 0; i < l1_size; i++) {
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uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
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bool l2_dirty = false;
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if (!l2_offset) {
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/* unallocated */
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continue;
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}
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if (is_active_l1) {
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/* get active L2 tables from cache */
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ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
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(void **)&l2_table);
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} else {
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/* load inactive L2 tables from disk */
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ret = bdrv_read(bs->file, l2_offset / BDRV_SECTOR_SIZE,
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(void *)l2_table, s->cluster_sectors);
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}
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if (ret < 0) {
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goto fail;
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}
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for (j = 0; j < s->l2_size; j++) {
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uint64_t l2_entry = be64_to_cpu(l2_table[j]);
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int64_t offset = l2_entry & L2E_OFFSET_MASK, cluster_index;
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int cluster_type = qcow2_get_cluster_type(l2_entry);
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if (cluster_type == QCOW2_CLUSTER_NORMAL) {
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cluster_index = offset >> s->cluster_bits;
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assert((cluster_index >= 0) && (cluster_index < nb_clusters));
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if (expanded_clusters[cluster_index / 8] &
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(1 << (cluster_index % 8))) {
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/* Probably a shared L2 table; this cluster was a zero
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* cluster which has been expanded, its refcount
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* therefore most likely requires an update. */
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ret = qcow2_update_cluster_refcount(bs, cluster_index, 1,
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QCOW2_DISCARD_NEVER);
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if (ret < 0) {
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goto fail;
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}
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/* Since we just increased the refcount, the COPIED flag may
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* no longer be set. */
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l2_table[j] = cpu_to_be64(l2_entry & ~QCOW_OFLAG_COPIED);
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l2_dirty = true;
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}
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continue;
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}
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else if (qcow2_get_cluster_type(l2_entry) != QCOW2_CLUSTER_ZERO) {
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continue;
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}
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if (!offset) {
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/* not preallocated */
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if (!bs->backing_hd) {
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/* not backed; therefore we can simply deallocate the
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* cluster */
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l2_table[j] = 0;
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l2_dirty = true;
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continue;
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}
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offset = qcow2_alloc_clusters(bs, s->cluster_size);
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if (offset < 0) {
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ret = offset;
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goto fail;
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}
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}
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ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT,
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offset, s->cluster_size);
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if (ret < 0) {
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qcow2_free_clusters(bs, offset, s->cluster_size,
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QCOW2_DISCARD_ALWAYS);
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goto fail;
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}
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ret = bdrv_write_zeroes(bs->file, offset / BDRV_SECTOR_SIZE,
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s->cluster_sectors);
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if (ret < 0) {
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qcow2_free_clusters(bs, offset, s->cluster_size,
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QCOW2_DISCARD_ALWAYS);
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goto fail;
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}
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l2_table[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED);
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l2_dirty = true;
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cluster_index = offset >> s->cluster_bits;
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assert((cluster_index >= 0) && (cluster_index < nb_clusters));
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expanded_clusters[cluster_index / 8] |= 1 << (cluster_index % 8);
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}
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if (is_active_l1) {
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if (l2_dirty) {
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qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
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qcow2_cache_depends_on_flush(s->l2_table_cache);
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}
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ret = qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
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if (ret < 0) {
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l2_table = NULL;
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goto fail;
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}
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} else {
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if (l2_dirty) {
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ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT &
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~(QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2), l2_offset,
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s->cluster_size);
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if (ret < 0) {
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goto fail;
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}
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ret = bdrv_write(bs->file, l2_offset / BDRV_SECTOR_SIZE,
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(void *)l2_table, s->cluster_sectors);
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if (ret < 0) {
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goto fail;
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}
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}
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}
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}
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ret = 0;
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fail:
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if (l2_table) {
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if (!is_active_l1) {
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qemu_vfree(l2_table);
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} else {
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if (ret < 0) {
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qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
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} else {
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ret = qcow2_cache_put(bs, s->l2_table_cache,
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(void **)&l2_table);
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}
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}
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}
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return ret;
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}
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/*
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* For backed images, expands all zero clusters on the image. For non-backed
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* images, deallocates all non-pre-allocated zero clusters (and claims the
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* allocation for pre-allocated ones). This is important for downgrading to a
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* qcow2 version which doesn't yet support metadata zero clusters.
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*/
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int qcow2_expand_zero_clusters(BlockDriverState *bs)
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{
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BDRVQcowState *s = bs->opaque;
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uint64_t *l1_table = NULL;
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int cluster_to_sector_bits = s->cluster_bits - BDRV_SECTOR_BITS;
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uint64_t nb_clusters;
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uint8_t *expanded_clusters;
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int ret;
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int i, j;
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nb_clusters = (bs->total_sectors + (1 << cluster_to_sector_bits) - 1)
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>> cluster_to_sector_bits;
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expanded_clusters = g_malloc0((nb_clusters + 7) / 8);
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ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size,
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expanded_clusters, nb_clusters);
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if (ret < 0) {
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goto fail;
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}
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/* Inactive L1 tables may point to active L2 tables - therefore it is
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* necessary to flush the L2 table cache before trying to access the L2
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* tables pointed to by inactive L1 entries (else we might try to expand
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* zero clusters that have already been expanded); furthermore, it is also
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* necessary to empty the L2 table cache, since it may contain tables which
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* are now going to be modified directly on disk, bypassing the cache.
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* qcow2_cache_empty() does both for us. */
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ret = qcow2_cache_empty(bs, s->l2_table_cache);
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if (ret < 0) {
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goto fail;
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}
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for (i = 0; i < s->nb_snapshots; i++) {
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int l1_sectors = (s->snapshots[i].l1_size * sizeof(uint64_t) +
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BDRV_SECTOR_SIZE - 1) / BDRV_SECTOR_SIZE;
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l1_table = g_realloc(l1_table, l1_sectors * BDRV_SECTOR_SIZE);
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ret = bdrv_read(bs->file, s->snapshots[i].l1_table_offset /
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BDRV_SECTOR_SIZE, (void *)l1_table, l1_sectors);
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if (ret < 0) {
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goto fail;
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}
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for (j = 0; j < s->snapshots[i].l1_size; j++) {
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be64_to_cpus(&l1_table[j]);
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}
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ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size,
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expanded_clusters, nb_clusters);
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if (ret < 0) {
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goto fail;
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}
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}
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ret = 0;
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fail:
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g_free(expanded_clusters);
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g_free(l1_table);
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return ret;
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}
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@ -601,10 +601,10 @@ fail:
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* If the return value is non-negative, it is the new refcount of the cluster.
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* If it is negative, it is -errno and indicates an error.
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*/
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static int update_cluster_refcount(BlockDriverState *bs,
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int64_t cluster_index,
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int addend,
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enum qcow2_discard_type type)
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int qcow2_update_cluster_refcount(BlockDriverState *bs,
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int64_t cluster_index,
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int addend,
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enum qcow2_discard_type type)
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{
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BDRVQcowState *s = bs->opaque;
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int ret;
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@ -733,8 +733,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
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if (free_in_cluster == 0)
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s->free_byte_offset = 0;
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if ((offset & (s->cluster_size - 1)) != 0)
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update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
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QCOW2_DISCARD_NEVER);
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qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
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QCOW2_DISCARD_NEVER);
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} else {
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offset = qcow2_alloc_clusters(bs, s->cluster_size);
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if (offset < 0) {
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@ -744,8 +744,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
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if ((cluster_offset + s->cluster_size) == offset) {
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/* we are lucky: contiguous data */
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offset = s->free_byte_offset;
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update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
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QCOW2_DISCARD_NEVER);
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qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,
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QCOW2_DISCARD_NEVER);
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s->free_byte_offset += size;
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} else {
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s->free_byte_offset = offset;
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@ -754,8 +754,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
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}
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/* The cluster refcount was incremented, either by qcow2_alloc_clusters()
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* or explicitly by update_cluster_refcount(). Refcount blocks must be
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* flushed before the caller's L2 table updates.
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* or explicitly by qcow2_update_cluster_refcount(). Refcount blocks must
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* be flushed before the caller's L2 table updates.
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*/
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qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
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return offset;
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@ -896,8 +896,9 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
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break;
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}
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if (addend != 0) {
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refcount = update_cluster_refcount(bs, cluster_index, addend,
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QCOW2_DISCARD_SNAPSHOT);
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refcount = qcow2_update_cluster_refcount(bs,
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cluster_index, addend,
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QCOW2_DISCARD_SNAPSHOT);
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} else {
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refcount = get_refcount(bs, cluster_index);
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}
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@ -936,8 +937,8 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
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if (addend != 0) {
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refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend,
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QCOW2_DISCARD_SNAPSHOT);
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refcount = qcow2_update_cluster_refcount(bs, l2_offset >>
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s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT);
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} else {
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refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
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}
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@ -411,6 +411,9 @@ int qcow2_update_header(BlockDriverState *bs);
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int qcow2_refcount_init(BlockDriverState *bs);
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void qcow2_refcount_close(BlockDriverState *bs);
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int qcow2_update_cluster_refcount(BlockDriverState *bs, int64_t cluster_index,
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int addend, enum qcow2_discard_type type);
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int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size);
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int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
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int nb_clusters);
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@ -458,6 +461,8 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
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int nb_sectors, enum qcow2_discard_type type);
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int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
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int qcow2_expand_zero_clusters(BlockDriverState *bs);
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/* qcow2-snapshot.c functions */
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int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
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int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
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