diff options
Diffstat (limited to 'block/qcow2-refcount.c')
| -rw-r--r-- | block/qcow2-refcount.c | 311 |
1 files changed, 305 insertions, 6 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index e96466635a..9bfc75e9cf 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -1688,6 +1688,285 @@ static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res, } /* + * Allocates clusters using an in-memory refcount table (IMRT) in contrast to + * the on-disk refcount structures. + * + * On input, *first_free_cluster tells where to start looking, and need not + * actually be a free cluster; the returned offset will not be before that + * cluster. On output, *first_free_cluster points to the first gap found, even + * if that gap was too small to be used as the returned offset. + * + * Note that *first_free_cluster is a cluster index whereas the return value is + * an offset. + */ +static int64_t alloc_clusters_imrt(BlockDriverState *bs, + int cluster_count, + uint16_t **refcount_table, + int64_t *imrt_nb_clusters, + int64_t *first_free_cluster) +{ + BDRVQcowState *s = bs->opaque; + int64_t cluster = *first_free_cluster, i; + bool first_gap = true; + int contiguous_free_clusters; + + /* Starting at *first_free_cluster, find a range of at least cluster_count + * continuously free clusters */ + for (contiguous_free_clusters = 0; + cluster < *imrt_nb_clusters && + contiguous_free_clusters < cluster_count; + cluster++) + { + if (!(*refcount_table)[cluster]) { + contiguous_free_clusters++; + if (first_gap) { + /* If this is the first free cluster found, update + * *first_free_cluster accordingly */ + *first_free_cluster = cluster; + first_gap = false; + } + } else if (contiguous_free_clusters) { + contiguous_free_clusters = 0; + } + } + + /* If contiguous_free_clusters is greater than zero, it contains the number + * of continuously free clusters until the current cluster; the first free + * cluster in the current "gap" is therefore + * cluster - contiguous_free_clusters */ + + /* If no such range could be found, grow the in-memory refcount table + * accordingly to append free clusters at the end of the image */ + if (contiguous_free_clusters < cluster_count) { + int64_t old_imrt_nb_clusters = *imrt_nb_clusters; + uint16_t *new_refcount_table; + + /* contiguous_free_clusters clusters are already empty at the image end; + * we need cluster_count clusters; therefore, we have to allocate + * cluster_count - contiguous_free_clusters new clusters at the end of + * the image (which is the current value of cluster; note that cluster + * may exceed old_imrt_nb_clusters if *first_free_cluster pointed beyond + * the image end) */ + *imrt_nb_clusters = cluster + cluster_count - contiguous_free_clusters; + new_refcount_table = g_try_realloc(*refcount_table, + *imrt_nb_clusters * + sizeof(**refcount_table)); + if (!new_refcount_table) { + *imrt_nb_clusters = old_imrt_nb_clusters; + return -ENOMEM; + } + *refcount_table = new_refcount_table; + + memset(*refcount_table + old_imrt_nb_clusters, 0, + (*imrt_nb_clusters - old_imrt_nb_clusters) * + sizeof(**refcount_table)); + } + + /* Go back to the first free cluster */ + cluster -= contiguous_free_clusters; + for (i = 0; i < cluster_count; i++) { + (*refcount_table)[cluster + i] = 1; + } + + return cluster << s->cluster_bits; +} + +/* + * Creates a new refcount structure based solely on the in-memory information + * given through *refcount_table. All necessary allocations will be reflected + * in that array. + * + * On success, the old refcount structure is leaked (it will be covered by the + * new refcount structure). + */ +static int rebuild_refcount_structure(BlockDriverState *bs, + BdrvCheckResult *res, + uint16_t **refcount_table, + int64_t *nb_clusters) +{ + BDRVQcowState *s = bs->opaque; + int64_t first_free_cluster = 0, reftable_offset = -1, cluster = 0; + int64_t refblock_offset, refblock_start, refblock_index; + uint32_t reftable_size = 0; + uint64_t *on_disk_reftable = NULL; + uint16_t *on_disk_refblock; + int i, ret = 0; + struct { + uint64_t reftable_offset; + uint32_t reftable_clusters; + } QEMU_PACKED reftable_offset_and_clusters; + + qcow2_cache_empty(bs, s->refcount_block_cache); + +write_refblocks: + for (; cluster < *nb_clusters; cluster++) { + if (!(*refcount_table)[cluster]) { + continue; + } + + refblock_index = cluster >> s->refcount_block_bits; + refblock_start = refblock_index << s->refcount_block_bits; + + /* Don't allocate a cluster in a refblock already written to disk */ + if (first_free_cluster < refblock_start) { + first_free_cluster = refblock_start; + } + refblock_offset = alloc_clusters_imrt(bs, 1, refcount_table, + nb_clusters, &first_free_cluster); + if (refblock_offset < 0) { + fprintf(stderr, "ERROR allocating refblock: %s\n", + strerror(-refblock_offset)); + res->check_errors++; + ret = refblock_offset; + goto fail; + } + + if (reftable_size <= refblock_index) { + uint32_t old_reftable_size = reftable_size; + uint64_t *new_on_disk_reftable; + + reftable_size = ROUND_UP((refblock_index + 1) * sizeof(uint64_t), + s->cluster_size) / sizeof(uint64_t); + new_on_disk_reftable = g_try_realloc(on_disk_reftable, + reftable_size * + sizeof(uint64_t)); + if (!new_on_disk_reftable) { + res->check_errors++; + ret = -ENOMEM; + goto fail; + } + on_disk_reftable = new_on_disk_reftable; + + memset(on_disk_reftable + old_reftable_size, 0, + (reftable_size - old_reftable_size) * sizeof(uint64_t)); + + /* The offset we have for the reftable is now no longer valid; + * this will leak that range, but we can easily fix that by running + * a leak-fixing check after this rebuild operation */ + reftable_offset = -1; + } + on_disk_reftable[refblock_index] = refblock_offset; + + /* If this is apparently the last refblock (for now), try to squeeze the + * reftable in */ + if (refblock_index == (*nb_clusters - 1) >> s->refcount_block_bits && + reftable_offset < 0) + { + uint64_t reftable_clusters = size_to_clusters(s, reftable_size * + sizeof(uint64_t)); + reftable_offset = alloc_clusters_imrt(bs, reftable_clusters, + refcount_table, nb_clusters, + &first_free_cluster); + if (reftable_offset < 0) { + fprintf(stderr, "ERROR allocating reftable: %s\n", + strerror(-reftable_offset)); + res->check_errors++; + ret = reftable_offset; + goto fail; + } + } + + ret = qcow2_pre_write_overlap_check(bs, 0, refblock_offset, + s->cluster_size); + if (ret < 0) { + fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret)); + goto fail; + } + + on_disk_refblock = qemu_blockalign0(bs->file, s->cluster_size); + for (i = 0; i < s->refcount_block_size && + refblock_start + i < *nb_clusters; i++) + { + on_disk_refblock[i] = + cpu_to_be16((*refcount_table)[refblock_start + i]); + } + + ret = bdrv_write(bs->file, refblock_offset / BDRV_SECTOR_SIZE, + (void *)on_disk_refblock, s->cluster_sectors); + qemu_vfree(on_disk_refblock); + if (ret < 0) { + fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret)); + goto fail; + } + + /* Go to the end of this refblock */ + cluster = refblock_start + s->refcount_block_size - 1; + } + + if (reftable_offset < 0) { + uint64_t post_refblock_start, reftable_clusters; + + post_refblock_start = ROUND_UP(*nb_clusters, s->refcount_block_size); + reftable_clusters = size_to_clusters(s, + reftable_size * sizeof(uint64_t)); + /* Not pretty but simple */ + if (first_free_cluster < post_refblock_start) { + first_free_cluster = post_refblock_start; + } + reftable_offset = alloc_clusters_imrt(bs, reftable_clusters, + refcount_table, nb_clusters, + &first_free_cluster); + if (reftable_offset < 0) { + fprintf(stderr, "ERROR allocating reftable: %s\n", + strerror(-reftable_offset)); + res->check_errors++; + ret = reftable_offset; + goto fail; + } + + goto write_refblocks; + } + + assert(on_disk_reftable); + + for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) { + cpu_to_be64s(&on_disk_reftable[refblock_index]); + } + + ret = qcow2_pre_write_overlap_check(bs, 0, reftable_offset, + reftable_size * sizeof(uint64_t)); + if (ret < 0) { + fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret)); + goto fail; + } + + assert(reftable_size < INT_MAX / sizeof(uint64_t)); + ret = bdrv_pwrite(bs->file, reftable_offset, on_disk_reftable, + reftable_size * sizeof(uint64_t)); + if (ret < 0) { + fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret)); + goto fail; + } + + /* Enter new reftable into the image header */ + cpu_to_be64w(&reftable_offset_and_clusters.reftable_offset, + reftable_offset); + cpu_to_be32w(&reftable_offset_and_clusters.reftable_clusters, + size_to_clusters(s, reftable_size * sizeof(uint64_t))); + ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, + refcount_table_offset), + &reftable_offset_and_clusters, + sizeof(reftable_offset_and_clusters)); + if (ret < 0) { + fprintf(stderr, "ERROR setting reftable: %s\n", strerror(-ret)); + goto fail; + } + + for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) { + be64_to_cpus(&on_disk_reftable[refblock_index]); + } + s->refcount_table = on_disk_reftable; + s->refcount_table_offset = reftable_offset; + s->refcount_table_size = reftable_size; + + return 0; + +fail: + g_free(on_disk_reftable); + return ret; +} + +/* * Checks an image for refcount consistency. * * Returns 0 if no errors are found, the number of errors in case the image is @@ -1697,6 +1976,7 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix) { BDRVQcowState *s = bs->opaque; + BdrvCheckResult pre_compare_res; int64_t size, highest_cluster, nb_clusters; uint16_t *refcount_table = NULL; bool rebuild = false; @@ -1723,14 +2003,33 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, goto fail; } - compare_refcounts(bs, res, fix, &rebuild, &highest_cluster, refcount_table, + /* In case we don't need to rebuild the refcount structure (but want to fix + * something), this function is immediately called again, in which case the + * result should be ignored */ + pre_compare_res = *res; + compare_refcounts(bs, res, 0, &rebuild, &highest_cluster, refcount_table, nb_clusters); - if (rebuild) { - fprintf(stderr, "ERROR need to rebuild refcount structures\n"); - res->check_errors++; - /* Just carry on, the rest does not rely on the on-disk refcount - * structures */ + if (rebuild && (fix & BDRV_FIX_ERRORS)) { + fprintf(stderr, "Rebuilding refcount structure\n"); + ret = rebuild_refcount_structure(bs, res, &refcount_table, + &nb_clusters); + if (ret < 0) { + goto fail; + } + } else if (fix) { + if (rebuild) { + fprintf(stderr, "ERROR need to rebuild refcount structures\n"); + res->check_errors++; + ret = -EIO; + goto fail; + } + + if (res->leaks || res->corruptions) { + *res = pre_compare_res; + compare_refcounts(bs, res, fix, &rebuild, &highest_cluster, + refcount_table, nb_clusters); + } } /* check OFLAG_COPIED */ |