diff options
Diffstat (limited to 'qemu/block/qcow2-snapshot.c')
| -rw-r--r-- | qemu/block/qcow2-snapshot.c | 734 |
1 files changed, 734 insertions, 0 deletions
diff --git a/qemu/block/qcow2-snapshot.c b/qemu/block/qcow2-snapshot.c new file mode 100644 index 000000000..b6f58c13e --- /dev/null +++ b/qemu/block/qcow2-snapshot.c @@ -0,0 +1,734 @@ +/* + * 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/block_int.h" +#include "block/qcow2.h" +#include "qemu/error-report.h" + +void qcow2_free_snapshots(BlockDriverState *bs) +{ + BDRVQcowState *s = bs->opaque; + int i; + + for(i = 0; i < s->nb_snapshots; i++) { + g_free(s->snapshots[i].name); + g_free(s->snapshots[i].id_str); + } + g_free(s->snapshots); + s->snapshots = NULL; + s->nb_snapshots = 0; +} + +int qcow2_read_snapshots(BlockDriverState *bs) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshotHeader h; + QCowSnapshotExtraData extra; + QCowSnapshot *sn; + int i, id_str_size, name_size; + int64_t offset; + uint32_t extra_data_size; + int ret; + + if (!s->nb_snapshots) { + s->snapshots = NULL; + s->snapshots_size = 0; + return 0; + } + + offset = s->snapshots_offset; + s->snapshots = g_new0(QCowSnapshot, s->nb_snapshots); + + for(i = 0; i < s->nb_snapshots; i++) { + /* Read statically sized part of the snapshot header */ + offset = align_offset(offset, 8); + ret = bdrv_pread(bs->file, offset, &h, sizeof(h)); + if (ret < 0) { + goto fail; + } + + offset += sizeof(h); + sn = s->snapshots + i; + sn->l1_table_offset = be64_to_cpu(h.l1_table_offset); + sn->l1_size = be32_to_cpu(h.l1_size); + sn->vm_state_size = be32_to_cpu(h.vm_state_size); + sn->date_sec = be32_to_cpu(h.date_sec); + sn->date_nsec = be32_to_cpu(h.date_nsec); + sn->vm_clock_nsec = be64_to_cpu(h.vm_clock_nsec); + extra_data_size = be32_to_cpu(h.extra_data_size); + + id_str_size = be16_to_cpu(h.id_str_size); + name_size = be16_to_cpu(h.name_size); + + /* Read extra data */ + ret = bdrv_pread(bs->file, offset, &extra, + MIN(sizeof(extra), extra_data_size)); + if (ret < 0) { + goto fail; + } + offset += extra_data_size; + + if (extra_data_size >= 8) { + sn->vm_state_size = be64_to_cpu(extra.vm_state_size_large); + } + + if (extra_data_size >= 16) { + sn->disk_size = be64_to_cpu(extra.disk_size); + } else { + sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE; + } + + /* Read snapshot ID */ + sn->id_str = g_malloc(id_str_size + 1); + ret = bdrv_pread(bs->file, offset, sn->id_str, id_str_size); + if (ret < 0) { + goto fail; + } + offset += id_str_size; + sn->id_str[id_str_size] = '\0'; + + /* Read snapshot name */ + sn->name = g_malloc(name_size + 1); + ret = bdrv_pread(bs->file, offset, sn->name, name_size); + if (ret < 0) { + goto fail; + } + offset += name_size; + sn->name[name_size] = '\0'; + + if (offset - s->snapshots_offset > QCOW_MAX_SNAPSHOTS_SIZE) { + ret = -EFBIG; + goto fail; + } + } + + assert(offset - s->snapshots_offset <= INT_MAX); + s->snapshots_size = offset - s->snapshots_offset; + return 0; + +fail: + qcow2_free_snapshots(bs); + return ret; +} + +/* add at the end of the file a new list of snapshots */ +static int qcow2_write_snapshots(BlockDriverState *bs) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshot *sn; + QCowSnapshotHeader h; + QCowSnapshotExtraData extra; + int i, name_size, id_str_size, snapshots_size; + struct { + uint32_t nb_snapshots; + uint64_t snapshots_offset; + } QEMU_PACKED header_data; + int64_t offset, snapshots_offset = 0; + int ret; + + /* compute the size of the snapshots */ + offset = 0; + for(i = 0; i < s->nb_snapshots; i++) { + sn = s->snapshots + i; + offset = align_offset(offset, 8); + offset += sizeof(h); + offset += sizeof(extra); + offset += strlen(sn->id_str); + offset += strlen(sn->name); + + if (offset > QCOW_MAX_SNAPSHOTS_SIZE) { + ret = -EFBIG; + goto fail; + } + } + + assert(offset <= INT_MAX); + snapshots_size = offset; + + /* Allocate space for the new snapshot list */ + snapshots_offset = qcow2_alloc_clusters(bs, snapshots_size); + offset = snapshots_offset; + if (offset < 0) { + ret = offset; + goto fail; + } + ret = bdrv_flush(bs); + if (ret < 0) { + goto fail; + } + + /* The snapshot list position has not yet been updated, so these clusters + * must indeed be completely free */ + ret = qcow2_pre_write_overlap_check(bs, 0, offset, snapshots_size); + if (ret < 0) { + goto fail; + } + + + /* Write all snapshots to the new list */ + for(i = 0; i < s->nb_snapshots; i++) { + sn = s->snapshots + i; + memset(&h, 0, sizeof(h)); + h.l1_table_offset = cpu_to_be64(sn->l1_table_offset); + h.l1_size = cpu_to_be32(sn->l1_size); + /* If it doesn't fit in 32 bit, older implementations should treat it + * as a disk-only snapshot rather than truncate the VM state */ + if (sn->vm_state_size <= 0xffffffff) { + h.vm_state_size = cpu_to_be32(sn->vm_state_size); + } + h.date_sec = cpu_to_be32(sn->date_sec); + h.date_nsec = cpu_to_be32(sn->date_nsec); + h.vm_clock_nsec = cpu_to_be64(sn->vm_clock_nsec); + h.extra_data_size = cpu_to_be32(sizeof(extra)); + + memset(&extra, 0, sizeof(extra)); + extra.vm_state_size_large = cpu_to_be64(sn->vm_state_size); + extra.disk_size = cpu_to_be64(sn->disk_size); + + id_str_size = strlen(sn->id_str); + name_size = strlen(sn->name); + assert(id_str_size <= UINT16_MAX && name_size <= UINT16_MAX); + h.id_str_size = cpu_to_be16(id_str_size); + h.name_size = cpu_to_be16(name_size); + offset = align_offset(offset, 8); + + ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h)); + if (ret < 0) { + goto fail; + } + offset += sizeof(h); + + ret = bdrv_pwrite(bs->file, offset, &extra, sizeof(extra)); + if (ret < 0) { + goto fail; + } + offset += sizeof(extra); + + ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size); + if (ret < 0) { + goto fail; + } + offset += id_str_size; + + ret = bdrv_pwrite(bs->file, offset, sn->name, name_size); + if (ret < 0) { + goto fail; + } + offset += name_size; + } + + /* + * Update the header to point to the new snapshot table. This requires the + * new table and its refcounts to be stable on disk. + */ + ret = bdrv_flush(bs); + if (ret < 0) { + goto fail; + } + + QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) != + offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots)); + + header_data.nb_snapshots = cpu_to_be32(s->nb_snapshots); + header_data.snapshots_offset = cpu_to_be64(snapshots_offset); + + ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots), + &header_data, sizeof(header_data)); + if (ret < 0) { + goto fail; + } + + /* free the old snapshot table */ + qcow2_free_clusters(bs, s->snapshots_offset, s->snapshots_size, + QCOW2_DISCARD_SNAPSHOT); + s->snapshots_offset = snapshots_offset; + s->snapshots_size = snapshots_size; + return 0; + +fail: + if (snapshots_offset > 0) { + qcow2_free_clusters(bs, snapshots_offset, snapshots_size, + QCOW2_DISCARD_ALWAYS); + } + return ret; +} + +static void find_new_snapshot_id(BlockDriverState *bs, + char *id_str, int id_str_size) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshot *sn; + int i; + unsigned long id, id_max = 0; + + for(i = 0; i < s->nb_snapshots; i++) { + sn = s->snapshots + i; + id = strtoul(sn->id_str, NULL, 10); + if (id > id_max) + id_max = id; + } + snprintf(id_str, id_str_size, "%lu", id_max + 1); +} + +static int find_snapshot_by_id_and_name(BlockDriverState *bs, + const char *id, + const char *name) +{ + BDRVQcowState *s = bs->opaque; + int i; + + if (id && name) { + for (i = 0; i < s->nb_snapshots; i++) { + if (!strcmp(s->snapshots[i].id_str, id) && + !strcmp(s->snapshots[i].name, name)) { + return i; + } + } + } else if (id) { + for (i = 0; i < s->nb_snapshots; i++) { + if (!strcmp(s->snapshots[i].id_str, id)) { + return i; + } + } + } else if (name) { + for (i = 0; i < s->nb_snapshots; i++) { + if (!strcmp(s->snapshots[i].name, name)) { + return i; + } + } + } + + return -1; +} + +static int find_snapshot_by_id_or_name(BlockDriverState *bs, + const char *id_or_name) +{ + int ret; + + ret = find_snapshot_by_id_and_name(bs, id_or_name, NULL); + if (ret >= 0) { + return ret; + } + return find_snapshot_by_id_and_name(bs, NULL, id_or_name); +} + +/* if no id is provided, a new one is constructed */ +int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshot *new_snapshot_list = NULL; + QCowSnapshot *old_snapshot_list = NULL; + QCowSnapshot sn1, *sn = &sn1; + int i, ret; + uint64_t *l1_table = NULL; + int64_t l1_table_offset; + + if (s->nb_snapshots >= QCOW_MAX_SNAPSHOTS) { + return -EFBIG; + } + + memset(sn, 0, sizeof(*sn)); + + /* Generate an ID */ + find_new_snapshot_id(bs, sn_info->id_str, sizeof(sn_info->id_str)); + + /* Check that the ID is unique */ + if (find_snapshot_by_id_and_name(bs, sn_info->id_str, NULL) >= 0) { + return -EEXIST; + } + + /* Populate sn with passed data */ + sn->id_str = g_strdup(sn_info->id_str); + sn->name = g_strdup(sn_info->name); + + sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE; + sn->vm_state_size = sn_info->vm_state_size; + sn->date_sec = sn_info->date_sec; + sn->date_nsec = sn_info->date_nsec; + sn->vm_clock_nsec = sn_info->vm_clock_nsec; + + /* Allocate the L1 table of the snapshot and copy the current one there. */ + l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t)); + if (l1_table_offset < 0) { + ret = l1_table_offset; + goto fail; + } + + sn->l1_table_offset = l1_table_offset; + sn->l1_size = s->l1_size; + + l1_table = g_try_new(uint64_t, s->l1_size); + if (s->l1_size && l1_table == NULL) { + ret = -ENOMEM; + goto fail; + } + + for(i = 0; i < s->l1_size; i++) { + l1_table[i] = cpu_to_be64(s->l1_table[i]); + } + + ret = qcow2_pre_write_overlap_check(bs, 0, sn->l1_table_offset, + s->l1_size * sizeof(uint64_t)); + if (ret < 0) { + goto fail; + } + + ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table, + s->l1_size * sizeof(uint64_t)); + if (ret < 0) { + goto fail; + } + + g_free(l1_table); + l1_table = NULL; + + /* + * Increase the refcounts of all clusters and make sure everything is + * stable on disk before updating the snapshot table to contain a pointer + * to the new L1 table. + */ + ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1); + if (ret < 0) { + goto fail; + } + + /* Append the new snapshot to the snapshot list */ + new_snapshot_list = g_new(QCowSnapshot, s->nb_snapshots + 1); + if (s->snapshots) { + memcpy(new_snapshot_list, s->snapshots, + s->nb_snapshots * sizeof(QCowSnapshot)); + old_snapshot_list = s->snapshots; + } + s->snapshots = new_snapshot_list; + s->snapshots[s->nb_snapshots++] = *sn; + + ret = qcow2_write_snapshots(bs); + if (ret < 0) { + g_free(s->snapshots); + s->snapshots = old_snapshot_list; + s->nb_snapshots--; + goto fail; + } + + g_free(old_snapshot_list); + + /* The VM state isn't needed any more in the active L1 table; in fact, it + * hurts by causing expensive COW for the next snapshot. */ + qcow2_discard_clusters(bs, qcow2_vm_state_offset(s), + align_offset(sn->vm_state_size, s->cluster_size) + >> BDRV_SECTOR_BITS, + QCOW2_DISCARD_NEVER, false); + +#ifdef DEBUG_ALLOC + { + BdrvCheckResult result = {0}; + qcow2_check_refcounts(bs, &result, 0); + } +#endif + return 0; + +fail: + g_free(sn->id_str); + g_free(sn->name); + g_free(l1_table); + + return ret; +} + +/* copy the snapshot 'snapshot_name' into the current disk image */ +int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshot *sn; + int i, snapshot_index; + int cur_l1_bytes, sn_l1_bytes; + int ret; + uint64_t *sn_l1_table = NULL; + + /* Search the snapshot */ + snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id); + if (snapshot_index < 0) { + return -ENOENT; + } + sn = &s->snapshots[snapshot_index]; + + if (sn->disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) { + error_report("qcow2: Loading snapshots with different disk " + "size is not implemented"); + ret = -ENOTSUP; + goto fail; + } + + /* + * Make sure that the current L1 table is big enough to contain the whole + * L1 table of the snapshot. If the snapshot L1 table is smaller, the + * current one must be padded with zeros. + */ + ret = qcow2_grow_l1_table(bs, sn->l1_size, true); + if (ret < 0) { + goto fail; + } + + cur_l1_bytes = s->l1_size * sizeof(uint64_t); + sn_l1_bytes = sn->l1_size * sizeof(uint64_t); + + /* + * Copy the snapshot L1 table to the current L1 table. + * + * Before overwriting the old current L1 table on disk, make sure to + * increase all refcounts for the clusters referenced by the new one. + * Decrease the refcount referenced by the old one only when the L1 + * table is overwritten. + */ + sn_l1_table = g_try_malloc0(cur_l1_bytes); + if (cur_l1_bytes && sn_l1_table == NULL) { + ret = -ENOMEM; + goto fail; + } + + ret = bdrv_pread(bs->file, sn->l1_table_offset, sn_l1_table, sn_l1_bytes); + if (ret < 0) { + goto fail; + } + + ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset, + sn->l1_size, 1); + if (ret < 0) { + goto fail; + } + + ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, + s->l1_table_offset, cur_l1_bytes); + if (ret < 0) { + goto fail; + } + + ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset, sn_l1_table, + cur_l1_bytes); + if (ret < 0) { + goto fail; + } + + /* + * Decrease refcount of clusters of current L1 table. + * + * At this point, the in-memory s->l1_table points to the old L1 table, + * whereas on disk we already have the new one. + * + * qcow2_update_snapshot_refcount special cases the current L1 table to use + * the in-memory data instead of really using the offset to load a new one, + * which is why this works. + */ + ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, + s->l1_size, -1); + + /* + * Now update the in-memory L1 table to be in sync with the on-disk one. We + * need to do this even if updating refcounts failed. + */ + for(i = 0;i < s->l1_size; i++) { + s->l1_table[i] = be64_to_cpu(sn_l1_table[i]); + } + + if (ret < 0) { + goto fail; + } + + g_free(sn_l1_table); + sn_l1_table = NULL; + + /* + * Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed + * when we decreased the refcount of the old snapshot. + */ + ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0); + if (ret < 0) { + goto fail; + } + +#ifdef DEBUG_ALLOC + { + BdrvCheckResult result = {0}; + qcow2_check_refcounts(bs, &result, 0); + } +#endif + return 0; + +fail: + g_free(sn_l1_table); + return ret; +} + +int qcow2_snapshot_delete(BlockDriverState *bs, + const char *snapshot_id, + const char *name, + Error **errp) +{ + BDRVQcowState *s = bs->opaque; + QCowSnapshot sn; + int snapshot_index, ret; + + /* Search the snapshot */ + snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name); + if (snapshot_index < 0) { + error_setg(errp, "Can't find the snapshot"); + return -ENOENT; + } + sn = s->snapshots[snapshot_index]; + + /* Remove it from the snapshot list */ + memmove(s->snapshots + snapshot_index, + s->snapshots + snapshot_index + 1, + (s->nb_snapshots - snapshot_index - 1) * sizeof(sn)); + s->nb_snapshots--; + ret = qcow2_write_snapshots(bs); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to remove snapshot from snapshot list"); + return ret; + } + + /* + * The snapshot is now unused, clean up. If we fail after this point, we + * won't recover but just leak clusters. + */ + g_free(sn.id_str); + g_free(sn.name); + + /* + * Now decrease the refcounts of clusters referenced by the snapshot and + * free the L1 table. + */ + ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset, + sn.l1_size, -1); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to free the cluster and L1 table"); + return ret; + } + qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t), + QCOW2_DISCARD_SNAPSHOT); + + /* must update the copied flag on the current cluster offsets */ + ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to update snapshot status in disk"); + return ret; + } + +#ifdef DEBUG_ALLOC + { + BdrvCheckResult result = {0}; + qcow2_check_refcounts(bs, &result, 0); + } +#endif + return 0; +} + +int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab) +{ + BDRVQcowState *s = bs->opaque; + QEMUSnapshotInfo *sn_tab, *sn_info; + QCowSnapshot *sn; + int i; + + if (!s->nb_snapshots) { + *psn_tab = NULL; + return s->nb_snapshots; + } + + sn_tab = g_new0(QEMUSnapshotInfo, s->nb_snapshots); + for(i = 0; i < s->nb_snapshots; i++) { + sn_info = sn_tab + i; + sn = s->snapshots + i; + pstrcpy(sn_info->id_str, sizeof(sn_info->id_str), + sn->id_str); + pstrcpy(sn_info->name, sizeof(sn_info->name), + sn->name); + sn_info->vm_state_size = sn->vm_state_size; + sn_info->date_sec = sn->date_sec; + sn_info->date_nsec = sn->date_nsec; + sn_info->vm_clock_nsec = sn->vm_clock_nsec; + } + *psn_tab = sn_tab; + return s->nb_snapshots; +} + +int qcow2_snapshot_load_tmp(BlockDriverState *bs, + const char *snapshot_id, + const char *name, + Error **errp) +{ + int i, snapshot_index; + BDRVQcowState *s = bs->opaque; + QCowSnapshot *sn; + uint64_t *new_l1_table; + int new_l1_bytes; + int ret; + + assert(bs->read_only); + + /* Search the snapshot */ + snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name); + if (snapshot_index < 0) { + error_setg(errp, + "Can't find snapshot"); + return -ENOENT; + } + sn = &s->snapshots[snapshot_index]; + + /* Allocate and read in the snapshot's L1 table */ + if (sn->l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) { + error_setg(errp, "Snapshot L1 table too large"); + return -EFBIG; + } + new_l1_bytes = sn->l1_size * sizeof(uint64_t); + new_l1_table = qemu_try_blockalign(bs->file, + align_offset(new_l1_bytes, 512)); + if (new_l1_table == NULL) { + return -ENOMEM; + } + + ret = bdrv_pread(bs->file, sn->l1_table_offset, new_l1_table, new_l1_bytes); + if (ret < 0) { + error_setg(errp, "Failed to read l1 table for snapshot"); + qemu_vfree(new_l1_table); + return ret; + } + + /* Switch the L1 table */ + qemu_vfree(s->l1_table); + + s->l1_size = sn->l1_size; + s->l1_table_offset = sn->l1_table_offset; + s->l1_table = new_l1_table; + + for(i = 0;i < s->l1_size; i++) { + be64_to_cpus(&s->l1_table[i]); + } + + return 0; +} |