Re: [Qemu-devel] [PATCH V4 2/6] qcow2: add error message in qcow2_write_snapshots()

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

 > On 14.10.2013 23:52, Wenchao Xia wrote:
>> The function still returns int since qcow2_snapshot_delete() will
>> return the number.
>>
>> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
>> ---
>>   block/qcow2-snapshot.c |   48 ++++++++++++++++++++++++++++++++++++++++++------
>>   1 files changed, 42 insertions(+), 6 deletions(-)
>>
>> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
>> index b373f9a..4bd494b 100644
>> --- a/block/qcow2-snapshot.c
>> +++ b/block/qcow2-snapshot.c
>> @@ -152,7 +152,7 @@ fail:
>>   }
>>
>>   /* add at the end of the file a new list of snapshots */
>> -static int qcow2_write_snapshots(BlockDriverState *bs)
>> +static int qcow2_write_snapshots(BlockDriverState *bs, Error **errp)
>>   {
>>       BDRVQcowState *s = bs->opaque;
>>       QCowSnapshot *sn;
>> @@ -183,10 +183,18 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
>>       offset = snapshots_offset;
>>       if (offset < 0) {
>>           ret = offset;
>> +        error_setg(errp,
>> +                   "Failed in allocation of cluster for snapshot list: "
>> +                   "%d (%s)",
>> +                   ret, strerror(-ret));
>
> Again, error_setg_errno() is your friend.
>
>>           goto fail;
>>       }
>>       ret = bdrv_flush(bs);
>>       if (ret < 0) {
>> +        error_setg(errp,
>> +                   "Failed in flush after snapshot list cluster allocation: "
>> +                   "%d (%s)",
>> +                   ret, strerror(-ret));
>>           goto fail;
>>       }
>>
>> @@ -194,6 +202,10 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
>>        * must indeed be completely free */
>>       ret = qcow2_pre_write_overlap_check(bs, 0, offset, snapshots_size);
>>       if (ret < 0) {
>> +        error_setg(errp,
>> +                   "Failed in overlap check for snapshot list cluster at %"
>> +                   PRIi64 " with size %d: %d (%s)",
>> +                   offset, snapshots_size, ret, strerror(-ret));
>>           goto fail;
>>       }
>>
>> @@ -227,24 +239,40 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
>>
>>           ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));
>>           if (ret < 0) {
>> +            error_setg(errp,
>> +                       "Failed in write of snapshot header at %"
>> +                       PRIi64 " with size %" PRIu64 ": %d (%s)",
>> +                       offset, sizeof(h), ret, strerror(-ret));
>
> Again, on 32 bit systems, sizeof(size_t) is generally 4 and not 8 (you
> may want to cast sizeof(h) to int and just use %d).
>

   Maybe caset as (int64_t)sizeof(h) to avoid possible incomplete value?

>>               goto fail;
>>           }
>>           offset += sizeof(h);
>>
>>           ret = bdrv_pwrite(bs->file, offset, &extra, sizeof(extra));
>>           if (ret < 0) {
>> +            error_setg(errp,
>> +                       "Failed in write of extra snapshot data at %"
>> +                       PRIi64 " with size %" PRIu64 ": %d (%s)",
>> +                       offset, sizeof(extra), ret, strerror(-ret));
>
> Same here.
>
>>               goto fail;
>>           }
>>           offset += sizeof(extra);
>>
>>           ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size);
>>           if (ret < 0) {
>> +            error_setg(errp,
>> +                       "Failed in write of snapshot id string at %"
>> +                       PRIi64 " with size %d: %d (%s)",
>> +                       offset, id_str_size, ret, strerror(-ret));
>>               goto fail;
>>           }
>>           offset += id_str_size;
>>
>>           ret = bdrv_pwrite(bs->file, offset, sn->name, name_size);
>>           if (ret < 0) {
>> +            error_setg(errp,
>> +                       "Failed in write of snapshot name string at %"
>> +                       PRIi64 " with size %d: %d (%s)",
>> +                       offset, name_size, ret, strerror(-ret));
>>               goto fail;
>>           }
>>           offset += name_size;
>> @@ -256,6 +284,9 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
>>        */
>>       ret = bdrv_flush(bs);
>>       if (ret < 0) {
>> +        error_setg(errp,
>> +                   "Failed in flush after snapshot list update: %d (%s)",
>> +                   ret, strerror(-ret));
>>           goto fail;
>>       }
>>
>> @@ -268,6 +299,11 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
>>       ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
>>                              &header_data, sizeof(header_data));
>>       if (ret < 0) {
>> +        error_setg(errp,
>> +                   "Failed in update of image header at %"
>> +                   PRIi64 " with size %" PRIu64 ":%d (%s)",
>> +                   offsetof(QCowHeader, nb_snapshots), sizeof(header_data),
>> +                   ret, strerror(-ret));
>
> And here (also applies to offsetof(), which returns size_t as well).
> Also, you forgot a space after the colon (although you should be using
> error_setg_errno() anyway).
>

   Will use error_setg_errno().


> Max
>
>>           goto fail;
>>       }
>>
>> @@ -283,6 +319,9 @@ fail:
>>           qcow2_free_clusters(bs, snapshots_offset, snapshots_size,
>>                               QCOW2_DISCARD_ALWAYS);
>>       }
>> +    if (errp) {
>> +        g_assert(error_is_set(errp));
>> +    }
>>       return ret;
>>   }
>>
>> @@ -446,10 +485,8 @@ void qcow2_snapshot_create(BlockDriverState *bs,
>>       s->snapshots = new_snapshot_list;
>>       s->snapshots[s->nb_snapshots++] = *sn;
>>
>> -    ret = qcow2_write_snapshots(bs);
>> +    ret = qcow2_write_snapshots(bs, errp);
>>       if (ret < 0) {
>> -        /* Following line will be replaced with more detailed error later */
>> -        error_setg(errp, "Failed in write of snapshot");
>>           g_free(s->snapshots);
>>           s->snapshots = old_snapshot_list;
>>           s->nb_snapshots--;
>> @@ -623,9 +660,8 @@ int qcow2_snapshot_delete(BlockDriverState *bs,
>>               s->snapshots + snapshot_index + 1,
>>               (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));
>>       s->nb_snapshots--;
>> -    ret = qcow2_write_snapshots(bs);
>> +    ret = qcow2_write_snapshots(bs, errp);
>>       if (ret < 0) {
>> -        error_setg(errp, "Failed to remove snapshot from snapshot list");
>>           return ret;
>>       }
>>
>
>