qcow2: Split out snapshot functions

qcow2-snapshot.c contains the code related to snapshotting.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 405 insertions, 0 deletions

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
new file mode 100644
index 0000000000..2883e5069f
--- /dev/null
+++ b/block/qcow2-snapshot.c
@@ -0,0 +1,405 @@
+/*
+ * 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"
+
+typedef struct __attribute__((packed)) QCowSnapshotHeader {
+    /* header is 8 byte aligned */
+    uint64_t l1_table_offset;
+
+    uint32_t l1_size;
+    uint16_t id_str_size;
+    uint16_t name_size;
+
+    uint32_t date_sec;
+    uint32_t date_nsec;
+
+    uint64_t vm_clock_nsec;
+
+    uint32_t vm_state_size;
+    uint32_t extra_data_size; /* for extension */
+    /* extra data follows */
+    /* id_str follows */
+    /* name follows  */
+} QCowSnapshotHeader;
+
+void qcow_free_snapshots(BlockDriverState *bs)
+{
+    BDRVQcowState *s = bs->opaque;
+    int i;
+
+    for(i = 0; i < s->nb_snapshots; i++) {
+        qemu_free(s->snapshots[i].name);
+        qemu_free(s->snapshots[i].id_str);
+    }
+    qemu_free(s->snapshots);
+    s->snapshots = NULL;
+    s->nb_snapshots = 0;
+}
+
+int qcow_read_snapshots(BlockDriverState *bs)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshotHeader h;
+    QCowSnapshot *sn;
+    int i, id_str_size, name_size;
+    int64_t offset;
+    uint32_t extra_data_size;
+
+    if (!s->nb_snapshots) {
+        s->snapshots = NULL;
+        s->snapshots_size = 0;
+        return 0;
+    }
+
+    offset = s->snapshots_offset;
+    s->snapshots = qemu_mallocz(s->nb_snapshots * sizeof(QCowSnapshot));
+    for(i = 0; i < s->nb_snapshots; i++) {
+        offset = align_offset(offset, 8);
+        if (bdrv_pread(s->hd, offset, &h, sizeof(h)) != sizeof(h))
+            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);
+
+        offset += extra_data_size;
+
+        sn->id_str = qemu_malloc(id_str_size + 1);
+        if (bdrv_pread(s->hd, offset, sn->id_str, id_str_size) != id_str_size)
+            goto fail;
+        offset += id_str_size;
+        sn->id_str[id_str_size] = '\0';
+
+        sn->name = qemu_malloc(name_size + 1);
+        if (bdrv_pread(s->hd, offset, sn->name, name_size) != name_size)
+            goto fail;
+        offset += name_size;
+        sn->name[name_size] = '\0';
+    }
+    s->snapshots_size = offset - s->snapshots_offset;
+    return 0;
+ fail:
+    qcow_free_snapshots(bs);
+    return -1;
+}
+
+/* add at the end of the file a new list of snapshots */
+static int qcow_write_snapshots(BlockDriverState *bs)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshot *sn;
+    QCowSnapshotHeader h;
+    int i, name_size, id_str_size, snapshots_size;
+    uint64_t data64;
+    uint32_t data32;
+    int64_t offset, snapshots_offset;
+
+    /* 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 += strlen(sn->id_str);
+        offset += strlen(sn->name);
+    }
+    snapshots_size = offset;
+
+    snapshots_offset = alloc_clusters(bs, snapshots_size);
+    offset = snapshots_offset;
+
+    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);
+        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);
+
+        id_str_size = strlen(sn->id_str);
+        name_size = strlen(sn->name);
+        h.id_str_size = cpu_to_be16(id_str_size);
+        h.name_size = cpu_to_be16(name_size);
+        offset = align_offset(offset, 8);
+        if (bdrv_pwrite(s->hd, offset, &h, sizeof(h)) != sizeof(h))
+            goto fail;
+        offset += sizeof(h);
+        if (bdrv_pwrite(s->hd, offset, sn->id_str, id_str_size) != id_str_size)
+            goto fail;
+        offset += id_str_size;
+        if (bdrv_pwrite(s->hd, offset, sn->name, name_size) != name_size)
+            goto fail;
+        offset += name_size;
+    }
+
+    /* update the various header fields */
+    data64 = cpu_to_be64(snapshots_offset);
+    if (bdrv_pwrite(s->hd, offsetof(QCowHeader, snapshots_offset),
+                    &data64, sizeof(data64)) != sizeof(data64))
+        goto fail;
+    data32 = cpu_to_be32(s->nb_snapshots);
+    if (bdrv_pwrite(s->hd, offsetof(QCowHeader, nb_snapshots),
+                    &data32, sizeof(data32)) != sizeof(data32))
+        goto fail;
+
+    /* free the old snapshot table */
+    free_clusters(bs, s->snapshots_offset, s->snapshots_size);
+    s->snapshots_offset = snapshots_offset;
+    s->snapshots_size = snapshots_size;
+    return 0;
+ fail:
+    return -1;
+}
+
+static void find_new_snapshot_id(BlockDriverState *bs,
+                                 char *id_str, int id_str_size)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshot *sn;
+    int i, 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, "%d", id_max + 1);
+}
+
+static int find_snapshot_by_id(BlockDriverState *bs, const char *id_str)
+{
+    BDRVQcowState *s = bs->opaque;
+    int i;
+
+    for(i = 0; i < s->nb_snapshots; i++) {
+        if (!strcmp(s->snapshots[i].id_str, id_str))
+            return i;
+    }
+    return -1;
+}
+
+static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
+{
+    BDRVQcowState *s = bs->opaque;
+    int i, ret;
+
+    ret = find_snapshot_by_id(bs, name);
+    if (ret >= 0)
+        return ret;
+    for(i = 0; i < s->nb_snapshots; i++) {
+        if (!strcmp(s->snapshots[i].name, name))
+            return i;
+    }
+    return -1;
+}
+
+/* if no id is provided, a new one is constructed */
+int qcow_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshot *snapshots1, sn1, *sn = &sn1;
+    int i, ret;
+    uint64_t *l1_table = NULL;
+
+    memset(sn, 0, sizeof(*sn));
+
+    if (sn_info->id_str[0] == '\0') {
+        /* compute a new 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(bs, sn_info->id_str) >= 0)
+        return -ENOENT;
+
+    sn->id_str = qemu_strdup(sn_info->id_str);
+    if (!sn->id_str)
+        goto fail;
+    sn->name = qemu_strdup(sn_info->name);
+    if (!sn->name)
+        goto fail;
+    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;
+
+    ret = update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
+    if (ret < 0)
+        goto fail;
+
+    /* create the L1 table of the snapshot */
+    sn->l1_table_offset = alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
+    sn->l1_size = s->l1_size;
+
+    l1_table = qemu_malloc(s->l1_size * sizeof(uint64_t));
+    for(i = 0; i < s->l1_size; i++) {
+        l1_table[i] = cpu_to_be64(s->l1_table[i]);
+    }
+    if (bdrv_pwrite(s->hd, sn->l1_table_offset,
+                    l1_table, s->l1_size * sizeof(uint64_t)) !=
+        (s->l1_size * sizeof(uint64_t)))
+        goto fail;
+    qemu_free(l1_table);
+    l1_table = NULL;
+
+    snapshots1 = qemu_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
+    if (s->snapshots) {
+        memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
+        qemu_free(s->snapshots);
+    }
+    s->snapshots = snapshots1;
+    s->snapshots[s->nb_snapshots++] = *sn;
+
+    if (qcow_write_snapshots(bs) < 0)
+        goto fail;
+#ifdef DEBUG_ALLOC
+    check_refcounts(bs);
+#endif
+    return 0;
+ fail:
+    qemu_free(sn->name);
+    qemu_free(l1_table);
+    return -1;
+}
+
+/* copy the snapshot 'snapshot_name' into the current disk image */
+int qcow_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshot *sn;
+    int i, snapshot_index, l1_size2;
+
+    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
+    if (snapshot_index < 0)
+        return -ENOENT;
+    sn = &s->snapshots[snapshot_index];
+
+    if (update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1) < 0)
+        goto fail;
+
+    if (grow_l1_table(bs, sn->l1_size) < 0)
+        goto fail;
+
+    s->l1_size = sn->l1_size;
+    l1_size2 = s->l1_size * sizeof(uint64_t);
+    /* copy the snapshot l1 table to the current l1 table */
+    if (bdrv_pread(s->hd, sn->l1_table_offset,
+                   s->l1_table, l1_size2) != l1_size2)
+        goto fail;
+    if (bdrv_pwrite(s->hd, s->l1_table_offset,
+                    s->l1_table, l1_size2) != l1_size2)
+        goto fail;
+    for(i = 0;i < s->l1_size; i++) {
+        be64_to_cpus(&s->l1_table[i]);
+    }
+
+    if (update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1) < 0)
+        goto fail;
+
+#ifdef DEBUG_ALLOC
+    check_refcounts(bs);
+#endif
+    return 0;
+ fail:
+    return -EIO;
+}
+
+int qcow_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowSnapshot *sn;
+    int snapshot_index, ret;
+
+    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
+    if (snapshot_index < 0)
+        return -ENOENT;
+    sn = &s->snapshots[snapshot_index];
+
+    ret = update_snapshot_refcount(bs, sn->l1_table_offset, sn->l1_size, -1);
+    if (ret < 0)
+        return ret;
+    /* must update the copied flag on the current cluster offsets */
+    ret = update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
+    if (ret < 0)
+        return ret;
+    free_clusters(bs, sn->l1_table_offset, sn->l1_size * sizeof(uint64_t));
+
+    qemu_free(sn->id_str);
+    qemu_free(sn->name);
+    memmove(sn, sn + 1, (s->nb_snapshots - snapshot_index - 1) * sizeof(*sn));
+    s->nb_snapshots--;
+    ret = qcow_write_snapshots(bs);
+    if (ret < 0) {
+        /* XXX: restore snapshot if error ? */
+        return ret;
+    }
+#ifdef DEBUG_ALLOC
+    check_refcounts(bs);
+#endif
+    return 0;
+}
+
+int qcow_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 = qemu_mallocz(s->nb_snapshots * sizeof(QEMUSnapshotInfo));
+    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;
+}
+