Re: [Qemu-devel] [PATCH V2 2/2] qcow2: cancel the modification on fail in qcow2_snapshot_create()

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

于 2013-5-17 17:27, Stefan Hajnoczi 写道:
> On Fri, May 17, 2013 at 03:56:45PM +0800, Wenchao Xia wrote:
>> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
>> ---
>>   block/qcow2-snapshot.c |   17 ++++++++++++++---
>>   1 files changed, 14 insertions(+), 3 deletions(-)
>>
>> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
>> index 45da32d..033f705 100644
>> --- a/block/qcow2-snapshot.c
>> +++ b/block/qcow2-snapshot.c
>> @@ -367,7 +367,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>       ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
>>                         s->l1_size * sizeof(uint64_t));
>>       if (ret < 0) {
>> -        goto fail;
>> +        goto dealloc_cluster;
>>       }
>>
>>       g_free(l1_table);
>> @@ -380,7 +380,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>        */
>>       ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
>>       if (ret < 0) {
>> -        goto fail;
>> +        goto dealloc_cluster;
>>       }
>>
>>       /* Append the new snapshot to the snapshot list */
>> @@ -397,7 +397,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>       if (ret < 0) {
>>           g_free(s->snapshots);
>>           s->snapshots = old_snapshot_list;
>> -        goto fail;
>> +        goto restore_refcount;
>>       }
>>
>>       g_free(old_snapshot_list);
>> @@ -410,6 +410,17 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>   #endif
>>       return 0;
>>
>> +restore_refcount:
>> +    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
>> +                                         s->l1_size, -1);
>> +    if (ret < 0) {
>> +        /* Nothing can be done none now, need image check later */
>> +        error_report("qcow2: Error in restoring refcount in snapshot");
>> +    }
>> +
>> +dealloc_cluster:
>> +    qcow2_free_clusters(bs, sn->l1_table_offset, sn->l1_size);
>
> sn->l1_size is in uint64_t units, not in bytes.
>
> Do you have test cases to exercise these code paths?  Use blkdebug to
> inject errors at the right point so that the error code path is taken.
>
   OK, I'll try it.

-- 
Best Regards

Wenchao Xia