Just call sd_create_branch() in the snapshot_goto to rollback the image is good enough. With this patch, 'loadvm' process for sheepdog is modified:
Suppose we have a snapshot chain A --> B --> C, we do 'loadvm A' so as to get a new chain, A --> B | V C1 in the old code: 1 reload inode of A (in snapshot_goto) 2 read vmstate via A's vdi_id (loadvm_state) 3 delete C and create C1, reload inode of C1 (sd_create_branch on write) with this patch applied: 1 reload inode of A, delete C and create C1 (in snapshot_goto) 2 read vmstate via C1's parent, that is A's vdi_id (loadvm_state) This will fix the possible bug that QEMU exit between 2 and 3 in the old code Cc: [email protected] Cc: MORITA Kazutaka <[email protected]> Cc: Kevin Wolf <[email protected]> Cc: Stefan Hajnoczi <[email protected]> Signed-off-by: Liu Yuan <[email protected]> --- block/sheepdog.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/block/sheepdog.c b/block/sheepdog.c index 94218ac..6d2cb9f 100644 --- a/block/sheepdog.c +++ b/block/sheepdog.c @@ -2071,14 +2071,11 @@ static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id) goto out; } - if (!s->inode.vm_state_size) { - error_report("Invalid snapshot"); - ret = -ENOENT; + ret = sd_create_branch(s); + if (ret) { goto out; } - s->is_snapshot = true; - g_free(old_s); return 0; @@ -2210,7 +2207,7 @@ static int do_load_save_vmstate(BDRVSheepdogState *s, uint8_t *data, data_len = MIN(remaining, SD_DATA_OBJ_SIZE - offset); - vmstate_oid = vid_to_vmstate_oid(s->inode.vdi_id, vdi_index); + vmstate_oid = vid_to_vmstate_oid(s->inode.parent_vdi_id, vdi_index); create = (offset == 0); if (load) { -- 1.7.9.5
