/* * Block driver for the QCOW version 2 format * * Copyright (c) 2004-2006 Fabrice Bellard * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include "qemu-common.h" #include "block_int.h" #include "block/qcow2.h" static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size); static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, int64_t offset, int64_t length, int addend); static int cache_refcount_updates = 0; static int write_refcount_block(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; size_t size = s->cluster_size; if (s->refcount_block_cache_offset == 0) { return 0; } BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE); if (bdrv_pwrite(bs->file, s->refcount_block_cache_offset, s->refcount_block_cache, size) != size) { return -EIO; } return 0; } /*********************************************************/ /* refcount handling */ int qcow2_refcount_init(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; int ret, refcount_table_size2, i; s->refcount_block_cache = qemu_malloc(s->cluster_size); refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t); s->refcount_table = qemu_malloc(refcount_table_size2); if (s->refcount_table_size > 0) { BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_LOAD); ret = bdrv_pread(bs->file, s->refcount_table_offset, s->refcount_table, refcount_table_size2); if (ret != refcount_table_size2) goto fail; for(i = 0; i < s->refcount_table_size; i++) be64_to_cpus(&s->refcount_table[i]); } return 0; fail: return -ENOMEM; } void qcow2_refcount_close(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; qemu_free(s->refcount_block_cache); qemu_free(s->refcount_table); } static int load_refcount_block(BlockDriverState *bs, int64_t refcount_block_offset) { BDRVQcowState *s = bs->opaque; int ret; if (cache_refcount_updates) { ret = write_refcount_block(bs); if (ret < 0) { return ret; } } BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD); ret = bdrv_pread(bs->file, refcount_block_offset, s->refcount_block_cache, s->cluster_size); if (ret < 0) { return ret; } s->refcount_block_cache_offset = refcount_block_offset; return 0; } /* * Returns the refcount of the cluster given by its index. Any non-negative * return value is the refcount of the cluster, negative values are -errno * and indicate an error. */ static int get_refcount(BlockDriverState *bs, int64_t cluster_index) { BDRVQcowState *s = bs->opaque; int refcount_table_index, block_index; int64_t refcount_block_offset; int ret; refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); if (refcount_table_index >= s->refcount_table_size) return 0; refcount_block_offset = s->refcount_table[refcount_table_index]; if (!refcount_block_offset) return 0; if (refcount_block_offset != s->refcount_block_cache_offset) { /* better than nothing: return allocated if read error */ ret = load_refcount_block(bs, refcount_block_offset); if (ret < 0) { return ret; } } block_index = cluster_index & ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); return be16_to_cpu(s->refcount_block_cache[block_index]); } /* * Rounds the refcount table size up to avoid growing the table for each single * refcount block that is allocated. */ static unsigned int next_refcount_table_size(BDRVQcowState *s, unsigned int min_size) { unsigned int min_clusters = (min_size >> (s->cluster_bits - 3)) + 1; unsigned int refcount_table_clusters = MAX(1, s->refcount_table_size >> (s->cluster_bits - 3)); while (min_clusters > refcount_table_clusters) { refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2; } return refcount_table_clusters << (s->cluster_bits - 3); } /* Checks if two offsets are described by the same refcount block */ static int in_same_refcount_block(BDRVQcowState *s, uint64_t offset_a, uint64_t offset_b) { uint64_t block_a = offset_a >> (2 * s->cluster_bits - REFCOUNT_SHIFT); uint64_t block_b = offset_b >> (2 * s->cluster_bits - REFCOUNT_SHIFT); return (block_a == block_b); } /* * Loads a refcount block. If it doesn't exist yet, it is allocated first * (including growing the refcount table if needed). * * Returns the offset of the refcount block on success or -errno in error case */ static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index) { BDRVQcowState *s = bs->opaque; unsigned int refcount_table_index; int ret; BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC); /* Find the refcount block for the given cluster */ refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); if (refcount_table_index < s->refcount_table_size) { uint64_t refcount_block_offset = s->refcount_table[refcount_table_index]; /* If it's already there, we're done */ if (refcount_block_offset) { if (refcount_block_offset != s->refcount_block_cache_offset) { ret = load_refcount_block(bs, refcount_block_offset); if (ret < 0) { return ret; } } return refcount_block_offset; } } /* * If we came here, we need to allocate something. Something is at least * a cluster for the new refcount block. It may also include a new refcount * table if the old refcount table is too small. * * Note that allocating clusters here needs some special care: * * - We can't use the normal qcow2_alloc_clusters(), it would try to * increase the refcount and very likely we would end up with an endless * recursion. Instead we must place the refcount blocks in a way that * they can describe them themselves. * * - We need to consider that at this point we are inside update_refcounts * and doing the initial refcount increase. This means that some clusters * have already been allocated by the caller, but their refcount isn't * accurate yet. free_cluster_index tells us where this allocation ends * as long as we don't overwrite it by freeing clusters. * * - alloc_clusters_noref and qcow2_free_clusters may load a different * refcount block into the cache */ if (cache_refcount_updates) { ret = write_refcount_block(bs); if (ret < 0) { return ret; } } /* Allocate the refcount block itself and mark it as used */ int64_t new_block = alloc_clusters_noref(bs, s->cluster_size); if (new_block < 0) { return new_block; } #ifdef DEBUG_ALLOC2 fprintf(stderr, "qcow2: Allocate refcount block %d for %" PRIx64 " at %" PRIx64 "\n", refcount_table_index, cluster_index << s->cluster_bits, new_block); #endif if (in_same_refcount_block(s, new_block, cluster_index << s->cluster_bits)) { /* Zero the new refcount block before updating it */ memset(s->refcount_block_cache, 0, s->cluster_size); s->refcount_block_cache_offset = new_block; /* The block describes itself, need to update the cache */ int block_index = (new_block >> s->cluster_bits) & ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); s->refcount_block_cache[block_index] = cpu_to_be16(1); } else { /* Described somewhere else. This can recurse at most twice before we * arrive at a block that describes itself. */ ret = update_refcount(bs, new_block, s->cluster_size, 1); if (ret < 0) { goto fail_block; } /* Initialize the new refcount block only after updating its refcount, * update_refcount uses the refcount cache itself */ memset(s->refcount_block_cache, 0, s->cluster_size); s->refcount_block_cache_offset = new_block; } /* Now the new refcount block needs to be written to disk */ BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE); ret = bdrv_pwrite(bs->file, new_block, s->refcount_block_cache, s->cluster_size); if (ret < 0) { goto fail_block; } /* If the refcount table is big enough, just hook the block up there */ if (refcount_table_index < s->refcount_table_size) { uint64_t data64 = cpu_to_be64(new_block); BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_HOOKUP); ret = bdrv_pwrite(bs->file, s->refcount_table_offset + refcount_table_index * sizeof(uint64_t), &data64, sizeof(data64)); if (ret < 0) { goto fail_block; } s->refcount_table[refcount_table_index] = new_block; return new_block; } /* * If we come here, we need to grow the refcount table. Again, a new * refcount table needs some space and we can't simply allocate to avoid * endless recursion. * * Therefore let's grab new refcount blocks at the end of the image, which * will describe themselves and the new refcount table. This way we can * reference them only in the new table and do the switch to the new * refcount table at once without producing an inconsistent state in * between. */ BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW); /* Calculate the number of refcount blocks needed so far */ uint64_t refcount_block_clusters = 1 << (s->cluster_bits - REFCOUNT_SHIFT); uint64_t blocks_used = (s->free_cluster_index + refcount_block_clusters - 1) / refcount_block_clusters; /* And now we need at least one block more for the new metadata */ uint64_t table_size = next_refcount_table_size(s, blocks_used + 1); uint64_t last_table_size; uint64_t blocks_clusters; do { uint64_t table_clusters = size_to_clusters(s, table_size); blocks_clusters = 1 + ((table_clusters + refcount_block_clusters - 1) / refcount_block_clusters); uint64_t meta_clusters = table_clusters + blocks_clusters; last_table_size = table_size; table_size = next_refcount_table_size(s, blocks_used + ((meta_clusters + refcount_block_clusters - 1) / refcount_block_clusters)); } while (last_table_size != table_size); #ifdef DEBUG_ALLOC2 fprintf(stderr, "qcow2: Grow refcount table %" PRId32 " => %" PRId64 "\n", s->refcount_table_size, table_size); #endif /* Create the new refcount table and blocks */ uint64_t meta_offset = (blocks_used * refcount_block_clusters) * s->cluster_size; uint64_t table_offset = meta_offset + blocks_clusters * s->cluster_size; uint16_t *new_blocks = qemu_mallocz(blocks_clusters * s->cluster_size); uint64_t *new_table = qemu_mallocz(table_size * sizeof(uint64_t)); assert(meta_offset >= (s->free_cluster_index * s->cluster_size)); /* Fill the new refcount table */ memcpy(new_table, s->refcount_table, s->refcount_table_size * sizeof(uint64_t)); new_table[refcount_table_index] = new_block; int i; for (i = 0; i < blocks_clusters; i++) { new_table[blocks_used + i] = meta_offset + (i * s->cluster_size); } /* Fill the refcount blocks */ uint64_t table_clusters = size_to_clusters(s, table_size * sizeof(uint64_t)); int block = 0; for (i = 0; i < table_clusters + blocks_clusters; i++) { new_blocks[block++] = cpu_to_be16(1); } /* Write refcount blocks to disk */ BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_BLOCKS); ret = bdrv_pwrite(bs->file, meta_offset, new_blocks, blocks_clusters * s->cluster_size); qemu_free(new_blocks); if (ret < 0) { goto fail_table; } /* Write refcount table to disk */ for(i = 0; i < table_size; i++) { cpu_to_be64s(&new_table[i]); } BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_TABLE); ret = bdrv_pwrite(bs->file, table_offset, new_table, table_size * sizeof(uint64_t)); if (ret < 0) { goto fail_table; } for(i = 0; i < table_size; i++) { cpu_to_be64s(&new_table[i]); } /* Hook up the new refcount table in the qcow2 header */ uint8_t data[12]; cpu_to_be64w((uint64_t*)data, table_offset); cpu_to_be32w((uint32_t*)(data + 8), table_clusters); BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE); ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, refcount_table_offset), data, sizeof(data)); if (ret < 0) { goto fail_table; } /* And switch it in memory */ uint64_t old_table_offset = s->refcount_table_offset; uint64_t old_table_size = s->refcount_table_size; qemu_free(s->refcount_table); s->refcount_table = new_table; s->refcount_table_size = table_size; s->refcount_table_offset = table_offset; /* Free old table. Remember, we must not change free_cluster_index */ uint64_t old_free_cluster_index = s->free_cluster_index; qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t)); s->free_cluster_index = old_free_cluster_index; ret = load_refcount_block(bs, new_block); if (ret < 0) { goto fail_block; } return new_block; fail_table: qemu_free(new_table); fail_block: s->refcount_block_cache_offset = 0; return ret; } #define REFCOUNTS_PER_SECTOR (512 >> REFCOUNT_SHIFT) static int write_refcount_block_entries(BlockDriverState *bs, int64_t refcount_block_offset, int first_index, int last_index) { BDRVQcowState *s = bs->opaque; size_t size; int ret; if (cache_refcount_updates) { return 0; } if (first_index < 0) { return 0; } first_index &= ~(REFCOUNTS_PER_SECTOR - 1); last_index = (last_index + REFCOUNTS_PER_SECTOR) & ~(REFCOUNTS_PER_SECTOR - 1); size = (last_index - first_index) << REFCOUNT_SHIFT; BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART); ret = bdrv_pwrite(bs->file, refcount_block_offset + (first_index << REFCOUNT_SHIFT), &s->refcount_block_cache[first_index], size); if (ret < 0) { return ret; } return 0; } /* XXX: cache several refcount block clusters ? */ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, int64_t offset, int64_t length, int addend) { BDRVQcowState *s = bs->opaque; int64_t start, last, cluster_offset; int64_t refcount_block_offset = 0; int64_t table_index = -1, old_table_index; int first_index = -1, last_index = -1; int ret; #ifdef DEBUG_ALLOC2 printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n", offset, length, addend); #endif if (length < 0) { return -EINVAL; } else if (length == 0) { return 0; } start = offset & ~(s->cluster_size - 1); last = (offset + length - 1) & ~(s->cluster_size - 1); for(cluster_offset = start; cluster_offset <= last; cluster_offset += s->cluster_size) { int block_index, refcount; int64_t cluster_index = cluster_offset >> s->cluster_bits; int64_t new_block; /* Only write refcount block to disk when we are done with it */ old_table_index = table_index; table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); if ((old_table_index >= 0) && (table_index != old_table_index)) { ret = write_refcount_block_entries(bs, refcount_block_offset, first_index, last_index); if (ret < 0) { return ret; } first_index = -1; last_index = -1; } /* Load the refcount block and allocate it if needed */ new_block = alloc_refcount_block(bs, cluster_index); if (new_block < 0) { ret = new_block; goto fail; } refcount_block_offset = new_block; /* we can update the count and save it */ block_index = cluster_index & ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); if (first_index == -1 || block_index < first_index) { first_index = block_index; } if (block_index > last_index) { last_index = block_index; } refcount = be16_to_cpu(s->refcount_block_cache[block_index]); refcount += addend; if (refcount < 0 || refcount > 0xffff) { ret = -EINVAL; goto fail; } if (refcount == 0 && cluster_index < s->free_cluster_index) { s->free_cluster_index = cluster_index; } s->refcount_block_cache[block_index] = cpu_to_be16(refcount); } ret = 0; fail: /* Write last changed block to disk */ if (refcount_block_offset != 0) { int wret; wret = write_refcount_block_entries(bs, refcount_block_offset, first_index, last_index); if (wret < 0) { return ret < 0 ? ret : wret; } } /* * Try do undo any updates if an error is returned (This may succeed in * some cases like ENOSPC for allocating a new refcount block) */ if (ret < 0) { int dummy; dummy = update_refcount(bs, offset, cluster_offset - offset, -addend); } return ret; } /* * Increases or decreases the refcount of a given cluster by one. * addend must be 1 or -1. * * If the return value is non-negative, it is the new refcount of the cluster. * If it is negative, it is -errno and indicates an error. */ static int update_cluster_refcount(BlockDriverState *bs, int64_t cluster_index, int addend) { BDRVQcowState *s = bs->opaque; int ret; ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend); if (ret < 0) { return ret; } return get_refcount(bs, cluster_index); } /*********************************************************/ /* cluster allocation functions */ /* return < 0 if error */ static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size) { BDRVQcowState *s = bs->opaque; int i, nb_clusters, refcount; nb_clusters = size_to_clusters(s, size); retry: for(i = 0; i < nb_clusters; i++) { int64_t next_cluster_index = s->free_cluster_index++; refcount = get_refcount(bs, next_cluster_index); if (refcount < 0) { return refcount; } else if (refcount != 0) { goto retry; } } #ifdef DEBUG_ALLOC2 printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n", size, (s->free_cluster_index - nb_clusters) << s->cluster_bits); #endif return (s->free_cluster_index - nb_clusters) << s->cluster_bits; } int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size) { int64_t offset; int ret; BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC); offset = alloc_clusters_noref(bs, size); if (offset < 0) { return offset; } ret = update_refcount(bs, offset, size, 1); if (ret < 0) { return ret; } return offset; } /* only used to allocate compressed sectors. We try to allocate contiguous sectors. size must be <= cluster_size */ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) { BDRVQcowState *s = bs->opaque; int64_t offset, cluster_offset; int free_in_cluster; BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES); assert(size > 0 && size <= s->cluster_size); if (s->free_byte_offset == 0) { s->free_byte_offset = qcow2_alloc_clusters(bs, s->cluster_size); if (s->free_byte_offset < 0) { return s->free_byte_offset; } } redo: free_in_cluster = s->cluster_size - (s->free_byte_offset & (s->cluster_size - 1)); if (size <= free_in_cluster) { /* enough space in current cluster */ offset = s->free_byte_offset; s->free_byte_offset += size; free_in_cluster -= size; if (free_in_cluster == 0) s->free_byte_offset = 0; if ((offset & (s->cluster_size - 1)) != 0) update_cluster_refcount(bs, offset >> s->cluster_bits, 1); } else { offset = qcow2_alloc_clusters(bs, s->cluster_size); if (offset < 0) { return offset; } cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1); if ((cluster_offset + s->cluster_size) == offset) { /* we are lucky: contiguous data */ offset = s->free_byte_offset; update_cluster_refcount(bs, offset >> s->cluster_bits, 1); s->free_byte_offset += size; } else { s->free_byte_offset = offset; goto redo; } } return offset; } void qcow2_free_clusters(BlockDriverState *bs, int64_t offset, int64_t size) { int ret; BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE); ret = update_refcount(bs, offset, size, -1); if (ret < 0) { fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret)); /* TODO Remember the clusters to free them later and avoid leaking */ } } /* * free_any_clusters * * free clusters according to its type: compressed or not * */ void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t cluster_offset, int nb_clusters) { BDRVQcowState *s = bs->opaque; /* free the cluster */ if (cluster_offset & QCOW_OFLAG_COMPRESSED) { int nb_csectors; nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1; qcow2_free_clusters(bs, (cluster_offset & s->cluster_offset_mask) & ~511, nb_csectors * 512); return; } qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits); return; } /*********************************************************/ /* snapshots and image creation */ void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset, int64_t size) { int refcount; int64_t start, last, cluster_offset; uint16_t *p; start = offset & ~(s->cluster_size - 1); last = (offset + size - 1) & ~(s->cluster_size - 1); for(cluster_offset = start; cluster_offset <= last; cluster_offset += s->cluster_size) { p = &s->refcount_block[cluster_offset >> s->cluster_bits]; refcount = be16_to_cpu(*p); refcount++; *p = cpu_to_be16(refcount); } } /* update the refcounts of snapshots and the copied flag */ int qcow2_update_snapshot_refcount(BlockDriverState *bs, int64_t l1_table_offset, int l1_size, int addend) { BDRVQcowState *s = bs->opaque; uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated; int64_t old_offset, old_l2_offset; int l2_size, i, j, l1_modified, l2_modified, nb_csectors, refcount; qcow2_l2_cache_reset(bs); cache_refcount_updates = 1; l2_table = NULL; l1_table = NULL; l1_size2 = l1_size * sizeof(uint64_t); if (l1_table_offset != s->l1_table_offset) { if (l1_size2 != 0) { l1_table = qemu_mallocz(align_offset(l1_size2, 512)); } else { l1_table = NULL; } l1_allocated = 1; if (bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2) != l1_size2) goto fail; for(i = 0;i < l1_size; i++) be64_to_cpus(&l1_table[i]); } else { assert(l1_size == s->l1_size); l1_table = s->l1_table; l1_allocated = 0; } l2_size = s->l2_size * sizeof(uint64_t); l2_table = qemu_malloc(l2_size); l1_modified = 0; for(i = 0; i < l1_size; i++) { l2_offset = l1_table[i]; if (l2_offset) { old_l2_offset = l2_offset; l2_offset &= ~QCOW_OFLAG_COPIED; l2_modified = 0; if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) goto fail; for(j = 0; j < s->l2_size; j++) { offset = be64_to_cpu(l2_table[j]); if (offset != 0) { old_offset = offset; offset &= ~QCOW_OFLAG_COPIED; if (offset & QCOW_OFLAG_COMPRESSED) { nb_csectors = ((offset >> s->csize_shift) & s->csize_mask) + 1; if (addend != 0) { int ret; ret = update_refcount(bs, (offset & s->cluster_offset_mask) & ~511, nb_csectors * 512, addend); if (ret < 0) { goto fail; } } /* compressed clusters are never modified */ refcount = 2; } else { if (addend != 0) { refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend); } else { refcount = get_refcount(bs, offset >> s->cluster_bits); } if (refcount < 0) { goto fail; } } if (refcount == 1) { offset |= QCOW_OFLAG_COPIED; } if (offset != old_offset) { l2_table[j] = cpu_to_be64(offset); l2_modified = 1; } } } if (l2_modified) { if (bdrv_pwrite(bs->file, l2_offset, l2_table, l2_size) != l2_size) goto fail; } if (addend != 0) { refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend); } else { refcount = get_refcount(bs, l2_offset >> s->cluster_bits); } if (refcount < 0) { goto fail; } else if (refcount == 1) { l2_offset |= QCOW_OFLAG_COPIED; } if (l2_offset != old_l2_offset) { l1_table[i] = l2_offset; l1_modified = 1; } } } if (l1_modified) { for(i = 0; i < l1_size; i++) cpu_to_be64s(&l1_table[i]); if (bdrv_pwrite(bs->file, l1_table_offset, l1_table, l1_size2) != l1_size2) goto fail; for(i = 0; i < l1_size; i++) be64_to_cpus(&l1_table[i]); } if (l1_allocated) qemu_free(l1_table); qemu_free(l2_table); cache_refcount_updates = 0; write_refcount_block(bs); return 0; fail: if (l1_allocated) qemu_free(l1_table); qemu_free(l2_table); cache_refcount_updates = 0; write_refcount_block(bs); return -EIO; } /*********************************************************/ /* refcount checking functions */ /* * Increases the refcount for a range of clusters in a given refcount table. * This is used to construct a temporary refcount table out of L1 and L2 tables * which can be compared the the refcount table saved in the image. * * Returns the number of errors in the image that were found */ static int inc_refcounts(BlockDriverState *bs, uint16_t *refcount_table, int refcount_table_size, int64_t offset, int64_t size) { BDRVQcowState *s = bs->opaque; int64_t start, last, cluster_offset; int k; int errors = 0; if (size <= 0) return 0; start = offset & ~(s->cluster_size - 1); last = (offset + size - 1) & ~(s->cluster_size - 1); for(cluster_offset = start; cluster_offset <= last; cluster_offset += s->cluster_size) { k = cluster_offset >> s->cluster_bits; if (k < 0 || k >= refcount_table_size) { fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", cluster_offset); errors++; } else { if (++refcount_table[k] == 0) { fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 "\n", cluster_offset); errors++; } } } return errors; } /* * Increases the refcount in the given refcount table for the all clusters * referenced in the L2 table. While doing so, performs some checks on L2 * entries. * * Returns the number of errors found by the checks or -errno if an internal * error occurred. */ static int check_refcounts_l2(BlockDriverState *bs, uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, int check_copied) { BDRVQcowState *s = bs->opaque; uint64_t *l2_table, offset; int i, l2_size, nb_csectors, refcount; int errors = 0; /* Read L2 table from disk */ l2_size = s->l2_size * sizeof(uint64_t); l2_table = qemu_malloc(l2_size); if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) goto fail; /* Do the actual checks */ for(i = 0; i < s->l2_size; i++) { offset = be64_to_cpu(l2_table[i]); if (offset != 0) { if (offset & QCOW_OFLAG_COMPRESSED) { /* Compressed clusters don't have QCOW_OFLAG_COPIED */ if (offset & QCOW_OFLAG_COPIED) { fprintf(stderr, "ERROR: cluster %" PRId64 ": " "copied flag must never be set for compressed " "clusters\n", offset >> s->cluster_bits); offset &= ~QCOW_OFLAG_COPIED; errors++; } /* Mark cluster as used */ nb_csectors = ((offset >> s->csize_shift) & s->csize_mask) + 1; offset &= s->cluster_offset_mask; errors += inc_refcounts(bs, refcount_table, refcount_table_size, offset & ~511, nb_csectors * 512); } else { /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ if (check_copied) { uint64_t entry = offset; offset &= ~QCOW_OFLAG_COPIED; refcount = get_refcount(bs, offset >> s->cluster_bits); if (refcount < 0) { fprintf(stderr, "Can't get refcount for offset %" PRIx64 ": %s\n", entry, strerror(-refcount)); } if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) { fprintf(stderr, "ERROR OFLAG_COPIED: offset=%" PRIx64 " refcount=%d\n", entry, refcount); errors++; } } /* Mark cluster as used */ offset &= ~QCOW_OFLAG_COPIED; errors += inc_refcounts(bs, refcount_table, refcount_table_size, offset, s->cluster_size); /* Correct offsets are cluster aligned */ if (offset & (s->cluster_size - 1)) { fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " "properly aligned; L2 entry corrupted.\n", offset); errors++; } } } } qemu_free(l2_table); return errors; fail: fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); qemu_free(l2_table); return -EIO; } /* * Increases the refcount for the L1 table, its L2 tables and all referenced * clusters in the given refcount table. While doing so, performs some checks * on L1 and L2 entries. * * Returns the number of errors found by the checks or -errno if an internal * error occurred. */ static int check_refcounts_l1(BlockDriverState *bs, uint16_t *refcount_table, int refcount_table_size, int64_t l1_table_offset, int l1_size, int check_copied) { BDRVQcowState *s = bs->opaque; uint64_t *l1_table, l2_offset, l1_size2; int i, refcount, ret; int errors = 0; l1_size2 = l1_size * sizeof(uint64_t); /* Mark L1 table as used */ errors += inc_refcounts(bs, refcount_table, refcount_table_size, l1_table_offset, l1_size2); /* Read L1 table entries from disk */ if (l1_size2 == 0) { l1_table = NULL; } else { l1_table = qemu_malloc(l1_size2); if (bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2) != l1_size2) goto fail; for(i = 0;i < l1_size; i++) be64_to_cpus(&l1_table[i]); } /* Do the actual checks */ for(i = 0; i < l1_size; i++) { l2_offset = l1_table[i]; if (l2_offset) { /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ if (check_copied) { refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED) >> s->cluster_bits); if (refcount < 0) { fprintf(stderr, "Can't get refcount for l2_offset %" PRIx64 ": %s\n", l2_offset, strerror(-refcount)); } if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) { fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64 " refcount=%d\n", l2_offset, refcount); errors++; } } /* Mark L2 table as used */ l2_offset &= ~QCOW_OFLAG_COPIED; errors += inc_refcounts(bs, refcount_table, refcount_table_size, l2_offset, s->cluster_size); /* L2 tables are cluster aligned */ if (l2_offset & (s->cluster_size - 1)) { fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " "cluster aligned; L1 entry corrupted\n", l2_offset); errors++; } /* Process and check L2 entries */ ret = check_refcounts_l2(bs, refcount_table, refcount_table_size, l2_offset, check_copied); if (ret < 0) { goto fail; } errors += ret; } } qemu_free(l1_table); return errors; fail: fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); qemu_free(l1_table); return -EIO; } /* * Checks an image for refcount consistency. * * Returns 0 if no errors are found, the number of errors in case the image is * detected as corrupted, and -errno when an internal error occured. */ int qcow2_check_refcounts(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; int64_t size; int nb_clusters, refcount1, refcount2, i; QCowSnapshot *sn; uint16_t *refcount_table; int ret, errors = 0; size = bdrv_getlength(bs->file); nb_clusters = size_to_clusters(s, size); refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t)); /* header */ errors += inc_refcounts(bs, refcount_table, nb_clusters, 0, s->cluster_size); /* current L1 table */ ret = check_refcounts_l1(bs, refcount_table, nb_clusters, s->l1_table_offset, s->l1_size, 1); if (ret < 0) { return ret; } errors += ret; /* snapshots */ for(i = 0; i < s->nb_snapshots; i++) { sn = s->snapshots + i; check_refcounts_l1(bs, refcount_table, nb_clusters, sn->l1_table_offset, sn->l1_size, 0); } errors += inc_refcounts(bs, refcount_table, nb_clusters, s->snapshots_offset, s->snapshots_size); /* refcount data */ errors += inc_refcounts(bs, refcount_table, nb_clusters, s->refcount_table_offset, s->refcount_table_size * sizeof(uint64_t)); for(i = 0; i < s->refcount_table_size; i++) { int64_t offset; offset = s->refcount_table[i]; /* Refcount blocks are cluster aligned */ if (offset & (s->cluster_size - 1)) { fprintf(stderr, "ERROR refcount block %d is not " "cluster aligned; refcount table entry corrupted\n", i); errors++; } if (offset != 0) { errors += inc_refcounts(bs, refcount_table, nb_clusters, offset, s->cluster_size); if (refcount_table[offset / s->cluster_size] != 1) { fprintf(stderr, "ERROR refcount block %d refcount=%d\n", i, refcount_table[offset / s->cluster_size]); } } } /* compare ref counts */ for(i = 0; i < nb_clusters; i++) { refcount1 = get_refcount(bs, i); if (refcount1 < 0) { fprintf(stderr, "Can't get refcount for cluster %d: %s\n", i, strerror(-refcount1)); } refcount2 = refcount_table[i]; if (refcount1 != refcount2) { fprintf(stderr, "ERROR cluster %d refcount=%d reference=%d\n", i, refcount1, refcount2); errors++; } } qemu_free(refcount_table); return errors; }