qcow2: Rebuild refcount structure during check
The previous commit introduced the "rebuild" variable to qcow2's implementation of the image consistency check. Now make use of this by adding a function which creates a completely new refcount structure based solely on the in-memory information gathered before. The old refcount structure will be leaked, however. This leak will be dealt with in a follow-up commit. 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
f307b2558f
commit
c7c0681bc8
@ -1687,6 +1687,285 @@ static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
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}
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}
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/*
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* Allocates clusters using an in-memory refcount table (IMRT) in contrast to
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* the on-disk refcount structures.
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*
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* On input, *first_free_cluster tells where to start looking, and need not
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* actually be a free cluster; the returned offset will not be before that
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* cluster. On output, *first_free_cluster points to the first gap found, even
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* if that gap was too small to be used as the returned offset.
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*
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* Note that *first_free_cluster is a cluster index whereas the return value is
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* an offset.
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*/
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static int64_t alloc_clusters_imrt(BlockDriverState *bs,
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int cluster_count,
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uint16_t **refcount_table,
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int64_t *imrt_nb_clusters,
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int64_t *first_free_cluster)
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{
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BDRVQcowState *s = bs->opaque;
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int64_t cluster = *first_free_cluster, i;
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bool first_gap = true;
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int contiguous_free_clusters;
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/* Starting at *first_free_cluster, find a range of at least cluster_count
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* continuously free clusters */
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for (contiguous_free_clusters = 0;
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cluster < *imrt_nb_clusters &&
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contiguous_free_clusters < cluster_count;
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cluster++)
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{
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if (!(*refcount_table)[cluster]) {
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contiguous_free_clusters++;
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if (first_gap) {
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/* If this is the first free cluster found, update
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* *first_free_cluster accordingly */
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*first_free_cluster = cluster;
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first_gap = false;
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}
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} else if (contiguous_free_clusters) {
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contiguous_free_clusters = 0;
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}
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}
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/* If contiguous_free_clusters is greater than zero, it contains the number
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* of continuously free clusters until the current cluster; the first free
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* cluster in the current "gap" is therefore
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* cluster - contiguous_free_clusters */
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/* If no such range could be found, grow the in-memory refcount table
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* accordingly to append free clusters at the end of the image */
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if (contiguous_free_clusters < cluster_count) {
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int64_t old_imrt_nb_clusters = *imrt_nb_clusters;
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uint16_t *new_refcount_table;
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/* contiguous_free_clusters clusters are already empty at the image end;
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* we need cluster_count clusters; therefore, we have to allocate
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* cluster_count - contiguous_free_clusters new clusters at the end of
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* the image (which is the current value of cluster; note that cluster
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* may exceed old_imrt_nb_clusters if *first_free_cluster pointed beyond
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* the image end) */
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*imrt_nb_clusters = cluster + cluster_count - contiguous_free_clusters;
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new_refcount_table = g_try_realloc(*refcount_table,
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*imrt_nb_clusters *
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sizeof(**refcount_table));
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if (!new_refcount_table) {
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*imrt_nb_clusters = old_imrt_nb_clusters;
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return -ENOMEM;
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}
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*refcount_table = new_refcount_table;
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memset(*refcount_table + old_imrt_nb_clusters, 0,
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(*imrt_nb_clusters - old_imrt_nb_clusters) *
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sizeof(**refcount_table));
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}
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/* Go back to the first free cluster */
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cluster -= contiguous_free_clusters;
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for (i = 0; i < cluster_count; i++) {
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(*refcount_table)[cluster + i] = 1;
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}
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return cluster << s->cluster_bits;
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}
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/*
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* Creates a new refcount structure based solely on the in-memory information
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* given through *refcount_table. All necessary allocations will be reflected
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* in that array.
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*
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* On success, the old refcount structure is leaked (it will be covered by the
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* new refcount structure).
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*/
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static int rebuild_refcount_structure(BlockDriverState *bs,
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BdrvCheckResult *res,
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uint16_t **refcount_table,
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int64_t *nb_clusters)
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{
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BDRVQcowState *s = bs->opaque;
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int64_t first_free_cluster = 0, reftable_offset = -1, cluster = 0;
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int64_t refblock_offset, refblock_start, refblock_index;
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uint32_t reftable_size = 0;
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uint64_t *on_disk_reftable = NULL;
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uint16_t *on_disk_refblock;
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int i, ret = 0;
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struct {
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uint64_t reftable_offset;
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uint32_t reftable_clusters;
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} QEMU_PACKED reftable_offset_and_clusters;
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qcow2_cache_empty(bs, s->refcount_block_cache);
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write_refblocks:
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for (; cluster < *nb_clusters; cluster++) {
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if (!(*refcount_table)[cluster]) {
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continue;
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}
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refblock_index = cluster >> s->refcount_block_bits;
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refblock_start = refblock_index << s->refcount_block_bits;
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/* Don't allocate a cluster in a refblock already written to disk */
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if (first_free_cluster < refblock_start) {
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first_free_cluster = refblock_start;
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}
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refblock_offset = alloc_clusters_imrt(bs, 1, refcount_table,
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nb_clusters, &first_free_cluster);
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if (refblock_offset < 0) {
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fprintf(stderr, "ERROR allocating refblock: %s\n",
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strerror(-refblock_offset));
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res->check_errors++;
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ret = refblock_offset;
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goto fail;
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}
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if (reftable_size <= refblock_index) {
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uint32_t old_reftable_size = reftable_size;
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uint64_t *new_on_disk_reftable;
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reftable_size = ROUND_UP((refblock_index + 1) * sizeof(uint64_t),
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s->cluster_size) / sizeof(uint64_t);
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new_on_disk_reftable = g_try_realloc(on_disk_reftable,
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reftable_size *
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sizeof(uint64_t));
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if (!new_on_disk_reftable) {
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res->check_errors++;
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ret = -ENOMEM;
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goto fail;
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}
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on_disk_reftable = new_on_disk_reftable;
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memset(on_disk_reftable + old_reftable_size, 0,
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(reftable_size - old_reftable_size) * sizeof(uint64_t));
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/* The offset we have for the reftable is now no longer valid;
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* this will leak that range, but we can easily fix that by running
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* a leak-fixing check after this rebuild operation */
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reftable_offset = -1;
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}
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on_disk_reftable[refblock_index] = refblock_offset;
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/* If this is apparently the last refblock (for now), try to squeeze the
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* reftable in */
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if (refblock_index == (*nb_clusters - 1) >> s->refcount_block_bits &&
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reftable_offset < 0)
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{
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uint64_t reftable_clusters = size_to_clusters(s, reftable_size *
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sizeof(uint64_t));
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reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,
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refcount_table, nb_clusters,
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&first_free_cluster);
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if (reftable_offset < 0) {
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fprintf(stderr, "ERROR allocating reftable: %s\n",
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strerror(-reftable_offset));
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res->check_errors++;
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ret = reftable_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, 0, refblock_offset,
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s->cluster_size);
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if (ret < 0) {
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fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));
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goto fail;
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}
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on_disk_refblock = qemu_blockalign0(bs->file, s->cluster_size);
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for (i = 0; i < s->refcount_block_size &&
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refblock_start + i < *nb_clusters; i++)
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{
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on_disk_refblock[i] =
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cpu_to_be16((*refcount_table)[refblock_start + i]);
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}
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ret = bdrv_write(bs->file, refblock_offset / BDRV_SECTOR_SIZE,
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(void *)on_disk_refblock, s->cluster_sectors);
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qemu_vfree(on_disk_refblock);
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if (ret < 0) {
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fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));
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goto fail;
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}
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/* Go to the end of this refblock */
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cluster = refblock_start + s->refcount_block_size - 1;
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}
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if (reftable_offset < 0) {
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uint64_t post_refblock_start, reftable_clusters;
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post_refblock_start = ROUND_UP(*nb_clusters, s->refcount_block_size);
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reftable_clusters = size_to_clusters(s,
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reftable_size * sizeof(uint64_t));
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/* Not pretty but simple */
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if (first_free_cluster < post_refblock_start) {
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first_free_cluster = post_refblock_start;
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}
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reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,
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refcount_table, nb_clusters,
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&first_free_cluster);
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if (reftable_offset < 0) {
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fprintf(stderr, "ERROR allocating reftable: %s\n",
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strerror(-reftable_offset));
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res->check_errors++;
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ret = reftable_offset;
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goto fail;
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}
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goto write_refblocks;
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}
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assert(on_disk_reftable);
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for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {
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cpu_to_be64s(&on_disk_reftable[refblock_index]);
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}
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ret = qcow2_pre_write_overlap_check(bs, 0, reftable_offset,
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reftable_size * sizeof(uint64_t));
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if (ret < 0) {
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fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));
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goto fail;
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}
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assert(reftable_size < INT_MAX / sizeof(uint64_t));
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ret = bdrv_pwrite(bs->file, reftable_offset, on_disk_reftable,
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reftable_size * sizeof(uint64_t));
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if (ret < 0) {
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fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));
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goto fail;
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}
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/* Enter new reftable into the image header */
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cpu_to_be64w(&reftable_offset_and_clusters.reftable_offset,
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reftable_offset);
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cpu_to_be32w(&reftable_offset_and_clusters.reftable_clusters,
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size_to_clusters(s, reftable_size * sizeof(uint64_t)));
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ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader,
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refcount_table_offset),
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&reftable_offset_and_clusters,
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sizeof(reftable_offset_and_clusters));
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if (ret < 0) {
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fprintf(stderr, "ERROR setting reftable: %s\n", strerror(-ret));
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goto fail;
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}
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for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {
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be64_to_cpus(&on_disk_reftable[refblock_index]);
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}
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s->refcount_table = on_disk_reftable;
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s->refcount_table_offset = reftable_offset;
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s->refcount_table_size = reftable_size;
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return 0;
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fail:
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g_free(on_disk_reftable);
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return ret;
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}
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/*
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* Checks an image for refcount consistency.
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*
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@ -1697,6 +1976,7 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
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BdrvCheckMode fix)
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{
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BDRVQcowState *s = bs->opaque;
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BdrvCheckResult pre_compare_res;
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int64_t size, highest_cluster, nb_clusters;
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uint16_t *refcount_table = NULL;
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bool rebuild = false;
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@ -1723,14 +2003,33 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
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goto fail;
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}
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compare_refcounts(bs, res, fix, &rebuild, &highest_cluster, refcount_table,
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/* In case we don't need to rebuild the refcount structure (but want to fix
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* something), this function is immediately called again, in which case the
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* result should be ignored */
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pre_compare_res = *res;
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compare_refcounts(bs, res, 0, &rebuild, &highest_cluster, refcount_table,
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nb_clusters);
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if (rebuild && (fix & BDRV_FIX_ERRORS)) {
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fprintf(stderr, "Rebuilding refcount structure\n");
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ret = rebuild_refcount_structure(bs, res, &refcount_table,
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&nb_clusters);
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if (ret < 0) {
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goto fail;
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}
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} else if (fix) {
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if (rebuild) {
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fprintf(stderr, "ERROR need to rebuild refcount structures\n");
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res->check_errors++;
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/* Just carry on, the rest does not rely on the on-disk refcount
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* structures */
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ret = -EIO;
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goto fail;
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}
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if (res->leaks || res->corruptions) {
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*res = pre_compare_res;
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compare_refcounts(bs, res, fix, &rebuild, &highest_cluster,
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refcount_table, nb_clusters);
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}
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}
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/* check OFLAG_COPIED */
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