diff options
Diffstat (limited to 'block/qcow2-refcount.c')
| -rw-r--r-- | block/qcow2-refcount.c | 447 |
1 files changed, 447 insertions, 0 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 820f412ab6..e4020c6dd1 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -2467,3 +2467,450 @@ int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset, return 0; } + +/* A pointer to a function of this type is given to walk_over_reftable(). That + * function will create refblocks and pass them to a RefblockFinishOp once they + * are completed (@refblock). @refblock_empty is set if the refblock is + * completely empty. + * + * Along with the refblock, a corresponding reftable entry is passed, in the + * reftable @reftable (which may be reallocated) at @reftable_index. + * + * @allocated should be set to true if a new cluster has been allocated. + */ +typedef int (RefblockFinishOp)(BlockDriverState *bs, uint64_t **reftable, + uint64_t reftable_index, uint64_t *reftable_size, + void *refblock, bool refblock_empty, + bool *allocated, Error **errp); + +/** + * This "operation" for walk_over_reftable() allocates the refblock on disk (if + * it is not empty) and inserts its offset into the new reftable. The size of + * this new reftable is increased as required. + */ +static int alloc_refblock(BlockDriverState *bs, uint64_t **reftable, + uint64_t reftable_index, uint64_t *reftable_size, + void *refblock, bool refblock_empty, bool *allocated, + Error **errp) +{ + BDRVQcow2State *s = bs->opaque; + int64_t offset; + + if (!refblock_empty && reftable_index >= *reftable_size) { + uint64_t *new_reftable; + uint64_t new_reftable_size; + + new_reftable_size = ROUND_UP(reftable_index + 1, + s->cluster_size / sizeof(uint64_t)); + if (new_reftable_size > QCOW_MAX_REFTABLE_SIZE / sizeof(uint64_t)) { + error_setg(errp, + "This operation would make the refcount table grow " + "beyond the maximum size supported by QEMU, aborting"); + return -ENOTSUP; + } + + new_reftable = g_try_realloc(*reftable, new_reftable_size * + sizeof(uint64_t)); + if (!new_reftable) { + error_setg(errp, "Failed to increase reftable buffer size"); + return -ENOMEM; + } + + memset(new_reftable + *reftable_size, 0, + (new_reftable_size - *reftable_size) * sizeof(uint64_t)); + + *reftable = new_reftable; + *reftable_size = new_reftable_size; + } + + if (!refblock_empty && !(*reftable)[reftable_index]) { + offset = qcow2_alloc_clusters(bs, s->cluster_size); + if (offset < 0) { + error_setg_errno(errp, -offset, "Failed to allocate refblock"); + return offset; + } + (*reftable)[reftable_index] = offset; + *allocated = true; + } + + return 0; +} + +/** + * This "operation" for walk_over_reftable() writes the refblock to disk at the + * offset specified by the new reftable's entry. It does not modify the new + * reftable or change any refcounts. + */ +static int flush_refblock(BlockDriverState *bs, uint64_t **reftable, + uint64_t reftable_index, uint64_t *reftable_size, + void *refblock, bool refblock_empty, bool *allocated, + Error **errp) +{ + BDRVQcow2State *s = bs->opaque; + int64_t offset; + int ret; + + if (reftable_index < *reftable_size && (*reftable)[reftable_index]) { + offset = (*reftable)[reftable_index]; + + ret = qcow2_pre_write_overlap_check(bs, 0, offset, s->cluster_size); + if (ret < 0) { + error_setg_errno(errp, -ret, "Overlap check failed"); + return ret; + } + + ret = bdrv_pwrite(bs->file->bs, offset, refblock, s->cluster_size); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to write refblock"); + return ret; + } + } else { + assert(refblock_empty); + } + + return 0; +} + +/** + * This function walks over the existing reftable and every referenced refblock; + * if @new_set_refcount is non-NULL, it is called for every refcount entry to + * create an equal new entry in the passed @new_refblock. Once that + * @new_refblock is completely filled, @operation will be called. + * + * @status_cb and @cb_opaque are used for the amend operation's status callback. + * @index is the index of the walk_over_reftable() calls and @total is the total + * number of walk_over_reftable() calls per amend operation. Both are used for + * calculating the parameters for the status callback. + * + * @allocated is set to true if a new cluster has been allocated. + */ +static int walk_over_reftable(BlockDriverState *bs, uint64_t **new_reftable, + uint64_t *new_reftable_index, + uint64_t *new_reftable_size, + void *new_refblock, int new_refblock_size, + int new_refcount_bits, + RefblockFinishOp *operation, bool *allocated, + Qcow2SetRefcountFunc *new_set_refcount, + BlockDriverAmendStatusCB *status_cb, + void *cb_opaque, int index, int total, + Error **errp) +{ + BDRVQcow2State *s = bs->opaque; + uint64_t reftable_index; + bool new_refblock_empty = true; + int refblock_index; + int new_refblock_index = 0; + int ret; + + for (reftable_index = 0; reftable_index < s->refcount_table_size; + reftable_index++) + { + uint64_t refblock_offset = s->refcount_table[reftable_index] + & REFT_OFFSET_MASK; + + status_cb(bs, (uint64_t)index * s->refcount_table_size + reftable_index, + (uint64_t)total * s->refcount_table_size, cb_opaque); + + if (refblock_offset) { + void *refblock; + + if (offset_into_cluster(s, refblock_offset)) { + qcow2_signal_corruption(bs, true, -1, -1, "Refblock offset %#" + PRIx64 " unaligned (reftable index: %#" + PRIx64 ")", refblock_offset, + reftable_index); + error_setg(errp, + "Image is corrupt (unaligned refblock offset)"); + return -EIO; + } + + ret = qcow2_cache_get(bs, s->refcount_block_cache, refblock_offset, + &refblock); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to retrieve refblock"); + return ret; + } + + for (refblock_index = 0; refblock_index < s->refcount_block_size; + refblock_index++) + { + uint64_t refcount; + + if (new_refblock_index >= new_refblock_size) { + /* new_refblock is now complete */ + ret = operation(bs, new_reftable, *new_reftable_index, + new_reftable_size, new_refblock, + new_refblock_empty, allocated, errp); + if (ret < 0) { + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + return ret; + } + + (*new_reftable_index)++; + new_refblock_index = 0; + new_refblock_empty = true; + } + + refcount = s->get_refcount(refblock, refblock_index); + if (new_refcount_bits < 64 && refcount >> new_refcount_bits) { + uint64_t offset; + + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + + offset = ((reftable_index << s->refcount_block_bits) + + refblock_index) << s->cluster_bits; + + error_setg(errp, "Cannot decrease refcount entry width to " + "%i bits: Cluster at offset %#" PRIx64 " has a " + "refcount of %" PRIu64, new_refcount_bits, + offset, refcount); + return -EINVAL; + } + + if (new_set_refcount) { + new_set_refcount(new_refblock, new_refblock_index++, + refcount); + } else { + new_refblock_index++; + } + new_refblock_empty = new_refblock_empty && refcount == 0; + } + + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + } else { + /* No refblock means every refcount is 0 */ + for (refblock_index = 0; refblock_index < s->refcount_block_size; + refblock_index++) + { + if (new_refblock_index >= new_refblock_size) { + /* new_refblock is now complete */ + ret = operation(bs, new_reftable, *new_reftable_index, + new_reftable_size, new_refblock, + new_refblock_empty, allocated, errp); + if (ret < 0) { + return ret; + } + + (*new_reftable_index)++; + new_refblock_index = 0; + new_refblock_empty = true; + } + + if (new_set_refcount) { + new_set_refcount(new_refblock, new_refblock_index++, 0); + } else { + new_refblock_index++; + } + } + } + } + + if (new_refblock_index > 0) { + /* Complete the potentially existing partially filled final refblock */ + if (new_set_refcount) { + for (; new_refblock_index < new_refblock_size; + new_refblock_index++) + { + new_set_refcount(new_refblock, new_refblock_index, 0); + } + } + + ret = operation(bs, new_reftable, *new_reftable_index, + new_reftable_size, new_refblock, new_refblock_empty, + allocated, errp); + if (ret < 0) { + return ret; + } + + (*new_reftable_index)++; + } + + status_cb(bs, (uint64_t)(index + 1) * s->refcount_table_size, + (uint64_t)total * s->refcount_table_size, cb_opaque); + + return 0; +} + +int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order, + BlockDriverAmendStatusCB *status_cb, + void *cb_opaque, Error **errp) +{ + BDRVQcow2State *s = bs->opaque; + Qcow2GetRefcountFunc *new_get_refcount; + Qcow2SetRefcountFunc *new_set_refcount; + void *new_refblock = qemu_blockalign(bs->file->bs, s->cluster_size); + uint64_t *new_reftable = NULL, new_reftable_size = 0; + uint64_t *old_reftable, old_reftable_size, old_reftable_offset; + uint64_t new_reftable_index = 0; + uint64_t i; + int64_t new_reftable_offset = 0, allocated_reftable_size = 0; + int new_refblock_size, new_refcount_bits = 1 << refcount_order; + int old_refcount_order; + int walk_index = 0; + int ret; + bool new_allocation; + + assert(s->qcow_version >= 3); + assert(refcount_order >= 0 && refcount_order <= 6); + + /* see qcow2_open() */ + new_refblock_size = 1 << (s->cluster_bits - (refcount_order - 3)); + + new_get_refcount = get_refcount_funcs[refcount_order]; + new_set_refcount = set_refcount_funcs[refcount_order]; + + + do { + int total_walks; + + new_allocation = false; + + /* At least we have to do this walk and the one which writes the + * refblocks; also, at least we have to do this loop here at least + * twice (normally), first to do the allocations, and second to + * determine that everything is correctly allocated, this then makes + * three walks in total */ + total_walks = MAX(walk_index + 2, 3); + + /* First, allocate the structures so they are present in the refcount + * structures */ + ret = walk_over_reftable(bs, &new_reftable, &new_reftable_index, + &new_reftable_size, NULL, new_refblock_size, + new_refcount_bits, &alloc_refblock, + &new_allocation, NULL, status_cb, cb_opaque, + walk_index++, total_walks, errp); + if (ret < 0) { + goto done; + } + + new_reftable_index = 0; + + if (new_allocation) { + if (new_reftable_offset) { + qcow2_free_clusters(bs, new_reftable_offset, + allocated_reftable_size * sizeof(uint64_t), + QCOW2_DISCARD_NEVER); + } + + new_reftable_offset = qcow2_alloc_clusters(bs, new_reftable_size * + sizeof(uint64_t)); + if (new_reftable_offset < 0) { + error_setg_errno(errp, -new_reftable_offset, + "Failed to allocate the new reftable"); + ret = new_reftable_offset; + goto done; + } + allocated_reftable_size = new_reftable_size; + } + } while (new_allocation); + + /* Second, write the new refblocks */ + ret = walk_over_reftable(bs, &new_reftable, &new_reftable_index, + &new_reftable_size, new_refblock, + new_refblock_size, new_refcount_bits, + &flush_refblock, &new_allocation, new_set_refcount, + status_cb, cb_opaque, walk_index, walk_index + 1, + errp); + if (ret < 0) { + goto done; + } + assert(!new_allocation); + + + /* Write the new reftable */ + ret = qcow2_pre_write_overlap_check(bs, 0, new_reftable_offset, + new_reftable_size * sizeof(uint64_t)); + if (ret < 0) { + error_setg_errno(errp, -ret, "Overlap check failed"); + goto done; + } + + for (i = 0; i < new_reftable_size; i++) { + cpu_to_be64s(&new_reftable[i]); + } + + ret = bdrv_pwrite(bs->file->bs, new_reftable_offset, new_reftable, + new_reftable_size * sizeof(uint64_t)); + + for (i = 0; i < new_reftable_size; i++) { + be64_to_cpus(&new_reftable[i]); + } + + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to write the new reftable"); + goto done; + } + + + /* Empty the refcount cache */ + ret = qcow2_cache_flush(bs, s->refcount_block_cache); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to flush the refblock cache"); + goto done; + } + + /* Update the image header to point to the new reftable; this only updates + * the fields which are relevant to qcow2_update_header(); other fields + * such as s->refcount_table or s->refcount_bits stay stale for now + * (because we have to restore everything if qcow2_update_header() fails) */ + old_refcount_order = s->refcount_order; + old_reftable_size = s->refcount_table_size; + old_reftable_offset = s->refcount_table_offset; + + s->refcount_order = refcount_order; + s->refcount_table_size = new_reftable_size; + s->refcount_table_offset = new_reftable_offset; + + ret = qcow2_update_header(bs); + if (ret < 0) { + s->refcount_order = old_refcount_order; + s->refcount_table_size = old_reftable_size; + s->refcount_table_offset = old_reftable_offset; + error_setg_errno(errp, -ret, "Failed to update the qcow2 header"); + goto done; + } + + /* Now update the rest of the in-memory information */ + old_reftable = s->refcount_table; + s->refcount_table = new_reftable; + + s->refcount_bits = 1 << refcount_order; + s->refcount_max = UINT64_C(1) << (s->refcount_bits - 1); + s->refcount_max += s->refcount_max - 1; + + s->refcount_block_bits = s->cluster_bits - (refcount_order - 3); + s->refcount_block_size = 1 << s->refcount_block_bits; + + s->get_refcount = new_get_refcount; + s->set_refcount = new_set_refcount; + + /* For cleaning up all old refblocks and the old reftable below the "done" + * label */ + new_reftable = old_reftable; + new_reftable_size = old_reftable_size; + new_reftable_offset = old_reftable_offset; + +done: + if (new_reftable) { + /* On success, new_reftable actually points to the old reftable (and + * new_reftable_size is the old reftable's size); but that is just + * fine */ + for (i = 0; i < new_reftable_size; i++) { + uint64_t offset = new_reftable[i] & REFT_OFFSET_MASK; + if (offset) { + qcow2_free_clusters(bs, offset, s->cluster_size, + QCOW2_DISCARD_OTHER); + } + } + g_free(new_reftable); + + if (new_reftable_offset > 0) { + qcow2_free_clusters(bs, new_reftable_offset, + new_reftable_size * sizeof(uint64_t), + QCOW2_DISCARD_OTHER); + } + } + + qemu_vfree(new_refblock); + return ret; +} |