Re: [Qemu-devel] [PATCH V4 1/6] snapshot: add parameter *errp in snapshot create

[Max Reitz <mreitz@redhat.com>]

On 04.11.2013 02:47, Wenchao Xia wrote:
> 于 2013/11/2 20:39, Max Reitz 写道:
>> On 14.10.2013 23:52, Wenchao Xia wrote:
>>> The return value is only used for error report before this patch,
>>> so change the function protype to return void.
>>>
>>> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
>>> ---
>>>   block/qcow2-snapshot.c    |   27 +++++++++++++++++++++++----
>>>   block/qcow2.h             |    4 +++-
>>>   block/rbd.c               |   21 ++++++++++++---------
>>>   block/sheepdog.c          |   29 ++++++++++++++++++++---------
>>>   block/snapshot.c          |   19 +++++++++++++------
>>>   blockdev.c                |   10 ++++------
>>>   include/block/block_int.h |    5 +++--
>>>   include/block/snapshot.h  |    5 +++--
>>>   qemu-img.c                |   10 ++++++----
>>>   savevm.c                  |   12 ++++++++----
>>>   10 files changed, 95 insertions(+), 47 deletions(-)
>>>
>>> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
>>> index 3529c68..b373f9a 100644
>>> --- a/block/qcow2-snapshot.c
>>> +++ b/block/qcow2-snapshot.c
>>> @@ -347,7 +347,9 @@ static int
>>> find_snapshot_by_id_or_name(BlockDriverState *bs,
>>>   }
>>>
>>>   /* if no id is provided, a new one is constructed */
>>> -int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo
>>> *sn_info)
>>> +void qcow2_snapshot_create(BlockDriverState *bs,
>>> +                           QEMUSnapshotInfo *sn_info,
>>> +                           Error **errp)
>>>   {
>>>       BDRVQcowState *s = bs->opaque;
>>>       QCowSnapshot *new_snapshot_list = NULL;
>>> @@ -366,7 +368,8 @@ int qcow2_snapshot_create(BlockDriverState *bs,
>>> QEMUSnapshotInfo *sn_info)
>>>
>>>       /* Check that the ID is unique */
>>>       if (find_snapshot_by_id_and_name(bs, sn_info->id_str, NULL) >=
>>> 0) {
>>> -        return -EEXIST;
>>> +        error_setg(errp, "Snapshot with id %s already exist",
>>> sn_info->id_str);
>>> +        return;
>>>       }
>>>
>>>       /* Populate sn with passed data */
>>> @@ -383,6 +386,9 @@ int qcow2_snapshot_create(BlockDriverState *bs,
>>> QEMUSnapshotInfo *sn_info)
>>>       l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size *
>>> sizeof(uint64_t));
>>>       if (l1_table_offset < 0) {
>>>           ret = l1_table_offset;
>>> +        error_setg(errp,
>>> +                   "Failed in allocation of snapshot L1 table: %d
>>> (%s)",
>>> +                   ret, strerror(-ret));
>>
>> You may want to use error_setg_errno instead (here and in many other
>> places in this patch).
>>
>
>   I forgot we have error_setg_errno(), will use it.
>
>>>           goto fail;
>>>       }
>>>
>>> @@ -397,12 +403,20 @@ int qcow2_snapshot_create(BlockDriverState
>>> *bs, QEMUSnapshotInfo *sn_info)
>>>       ret = qcow2_pre_write_overlap_check(bs, 0, sn->l1_table_offset,
>>>                                           s->l1_size *
>>> sizeof(uint64_t));
>>>       if (ret < 0) {
>>> +        error_setg(errp, "Failed in overlap check for snapshot L1
>>> table at %"
>>> +                   PRIu64 " with size %" PRIu64 ": %d (%s)",
>>> +                   sn->l1_table_offset, s->l1_size * sizeof(uint64_t),
>>> +                   ret, strerror(-ret));
>>
>> s->l1_size * sizeof(uint64_t) is of the same type as uint64_t (PRIu64)
>> only on 64 bit systems. On 32 bit systems, it probably is the same as
>> uint32_t (because of a different size_t width).
>
>   I haven't a 32 bit system at hand to test, do you think
> (int64_t)(s->l1_size * sizeof(uint64_t))
>   could work for both 32 bit and 64 bit system?

Yes, that should work (although uint64_t would be more appropriate for
PRIu64).

>
>>
>>>           goto fail;
>>>       }
>>>
>>>       ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
>>>                         s->l1_size * sizeof(uint64_t));
>>>       if (ret < 0) {
>>> +        error_setg(errp, "Failed in update of snapshot L1 table at %"
>>> +                   PRIu64 " with size %" PRIu64 ": %d (%s)",
>>> +                   sn->l1_table_offset, s->l1_size * sizeof(uint64_t),
>>> +                   ret, strerror(-ret));
>>
>> Same here.
>>
>>>           goto fail;
>>>       }
>>>
>>> @@ -416,6 +430,9 @@ 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) {
>>> +        error_setg(errp, "Failed in update of refcount for snapshot
>>> at %"
>>> +                   PRIu64 " with size %d: %d (%s)",
>>> +                   s->l1_table_offset, s->l1_size,  ret,
>>> strerror(-ret));
>>>           goto fail;
>>>       }
>>>
>>> @@ -431,6 +448,8 @@ int qcow2_snapshot_create(BlockDriverState *bs,
>>> QEMUSnapshotInfo *sn_info)
>>>
>>>       ret = qcow2_write_snapshots(bs);
>>>       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--;
>>> @@ -452,14 +471,14 @@ int qcow2_snapshot_create(BlockDriverState
>>> *bs, QEMUSnapshotInfo *sn_info)
>>>         qcow2_check_refcounts(bs, &result, 0);
>>>       }
>>>   #endif
>>> -    return 0;
>>> +    return;
>>>
>>>   fail:
>>>       g_free(sn->id_str);
>>>       g_free(sn->name);
>>>       g_free(l1_table);
>>>
>>> -    return ret;
>>> +    return;
>>>   }
>>>
>>>   /* copy the snapshot 'snapshot_name' into the current disk image */
>>> diff --git a/block/qcow2.h b/block/qcow2.h
>>> index 922e190..c0a3d01 100644
>>> --- a/block/qcow2.h
>>> +++ b/block/qcow2.h
>>> @@ -481,7 +481,9 @@ int qcow2_zero_clusters(BlockDriverState *bs,
>>> uint64_t offset, int nb_sectors);
>>>   int qcow2_expand_zero_clusters(BlockDriverState *bs);
>>>
>>>   /* qcow2-snapshot.c functions */
>>> -int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo
>>> *sn_info);
>>> +void qcow2_snapshot_create(BlockDriverState *bs,
>>> +                           QEMUSnapshotInfo *sn_info,
>>> +                           Error **errp);
>>>   int qcow2_snapshot_goto(BlockDriverState *bs, const char
>>> *snapshot_id);
>>>   int qcow2_snapshot_delete(BlockDriverState *bs,
>>>                             const char *snapshot_id,
>>> diff --git a/block/rbd.c b/block/rbd.c
>>> index 4a1ea5b..6181999 100644
>>> --- a/block/rbd.c
>>> +++ b/block/rbd.c
>>> @@ -860,14 +860,16 @@ static int qemu_rbd_truncate(BlockDriverState
>>> *bs, int64_t offset)
>>>       return 0;
>>>   }
>>>
>>> -static int qemu_rbd_snap_create(BlockDriverState *bs,
>>> -                                QEMUSnapshotInfo *sn_info)
>>> +static void qemu_rbd_snap_create(BlockDriverState *bs,
>>> +                                 QEMUSnapshotInfo *sn_info,
>>> +                                 Error **errp)
>>>   {
>>>       BDRVRBDState *s = bs->opaque;
>>>       int r;
>>>
>>>       if (sn_info->name[0] == '\0') {
>>> -        return -EINVAL; /* we need a name for rbd snapshots */
>>> +        error_setg(errp, "rbd snapshot need a valid name");
>>
>> *needs (or "requires")
>>
>
>   will change.
>
>>> +        return; /* we need a name for rbd snapshots */
>>>       }
>>>
>>>       /*
>>> @@ -876,20 +878,21 @@ static int
>>> qemu_rbd_snap_create(BlockDriverState *bs,
>>>        */
>>>       if (sn_info->id_str[0] != '\0' &&
>>>           strcmp(sn_info->id_str, sn_info->name) != 0) {
>>> -        return -EINVAL;
>>> +        error_setg(errp, "rbd snapshot id should be empty or equal
>>> to name");
>>> +        return;
>>>       }
>>>
>>>       if (strlen(sn_info->name) >= sizeof(sn_info->id_str)) {
>>> -        return -ERANGE;
>>> +        error_setg(errp, "rbd snapshot name is too long");
>>> +        return;
>>>       }
>>>
>>>       r = rbd_snap_create(s->image, sn_info->name);
>>>       if (r < 0) {
>>> -        error_report("failed to create snap: %s", strerror(-r));
>>> -        return r;
>>> +        error_setg(errp,
>>> +                   "Failed to create snapshot: %d (%s)",
>>> +                   r, strerror(-r));
>>>       }
>>> -
>>> -    return 0;
>>>   }
>>>
>>>   static int qemu_rbd_snap_remove(BlockDriverState *bs,
>>> diff --git a/block/sheepdog.c b/block/sheepdog.c
>>> index 5f81c93..67aaeb7 100644
>>> --- a/block/sheepdog.c
>>> +++ b/block/sheepdog.c
>>> @@ -1961,7 +1961,9 @@ static int coroutine_fn
>>> sd_co_flush_to_disk(BlockDriverState *bs)
>>>       return acb->ret;
>>>   }
>>>
>>> -static int sd_snapshot_create(BlockDriverState *bs,
>>> QEMUSnapshotInfo *sn_info)
>>> +static void sd_snapshot_create(BlockDriverState *bs,
>>> +                               QEMUSnapshotInfo *sn_info,
>>> +                               Error **errp)
>>>   {
>>>       BDRVSheepdogState *s = bs->opaque;
>>>       int ret, fd;
>>> @@ -1974,10 +1976,10 @@ static int
>>> sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>>               s->name, sn_info->vm_state_size, s->is_snapshot);
>>>
>>>       if (s->is_snapshot) {
>>> -        error_report("You can't create a snapshot of a snapshot VDI, "
>>> -                     "%s (%" PRIu32 ").", s->name, s->inode.vdi_id);
>>> +        error_setg(errp, "You can't create a snapshot of a snapshot
>>> VDI, "
>>> +                   "%s (%" PRIu32 ")", s->name, s->inode.vdi_id);
>>>
>>> -        return -EINVAL;
>>> +        return;
>>>       }
>>>
>>>       DPRINTF("%s %s\n", sn_info->name, sn_info->id_str);
>>> @@ -1995,21 +1997,27 @@ static int
>>> sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>>       fd = connect_to_sdog(s);
>>>       if (fd < 0) {
>>>           ret = fd;
>>> +        error_setg(errp, "Failed to connect: %d (%s)", ret,
>>> strerror(-ret));
>>
>> You may remove the "ret = fd" line before the error_setg(), if you want
>> to; but then you'd have to replace the ret in the error_setg() by fd (it
>> should be an error_setg_errno() again, anyway). Do as you please.
>>
>
>   The function is return void now, it seems "ret = fd" can be
> removed, will do that.
>
>>>           goto cleanup;
>>>       }
>>>
>>>       ret = write_object(fd, (char *)&s->inode,
>>> vid_to_vdi_oid(s->inode.vdi_id),
>>>                          s->inode.nr_copies, datalen, 0, false,
>>> s->cache_flags);
>>>       if (ret < 0) {
>>> -        error_report("failed to write snapshot's inode.");
>>> +        error_setg(errp,
>>> +                   "Failed to write snapshot's inode: %d (%s)",
>>> +                   ret, strerror(-ret));
>>>           goto cleanup;
>>>       }
>>>
>>>       ret = do_sd_create(s, s->name, s->inode.vdi_size,
>>> s->inode.vdi_id, &new_vid,
>>>                          1);
>>>       if (ret < 0) {
>>> -        error_report("failed to create inode for snapshot. %s",
>>> -                     strerror(errno));
>>> +        error_setg(errp,
>>> +                   "Failed to create inode for snapshot: %d (%s), "
>>> +                   "errno %d (%s)",
>>> +                   ret, strerror(-ret),
>>> +                   errno, strerror(errno));
>>
>> This and the following hunk are actually places, where error_setg()
>> seems better than error_setg_errno() (because it's unclear whether -ret
>> or errno contains the true error value).
>>
>   I guess change it as:
> +        error_setg(errp,
> +                   "Failed to create inode for snapshot, return is %d",
> +                   ret);
>
>   ?

No, I think you should leave the hunk as it is. Apparently we don't know
whether the error value will be returned in ret or errno, so we need do
display both. I was just commenting on that you should indeed leave this
and the following hunk as they are and not replace them with
error_setg_errno(), since they actually have to display two error values.

Max

>
>> Max
>>
>>>           goto cleanup;
>>>       }
>>>
>>> @@ -2019,7 +2027,10 @@ static int
>>> sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
>>>                         s->inode.nr_copies, datalen, 0,
>>> s->cache_flags);
>>>
>>>       if (ret < 0) {
>>> -        error_report("failed to read new inode info. %s",
>>> strerror(errno));
>>> +        error_setg(errp, "Failed to read new inode info: %d (%s), "
>>> +                   "errno %d (%s)",
>>> +                   ret, strerror(-ret),
>>> +                   errno, strerror(errno));
>>>           goto cleanup;
>>>       }
>>>
>>> @@ -2029,7 +2040,7 @@ static int sd_snapshot_create(BlockDriverState
>>> *bs, QEMUSnapshotInfo *sn_info)
>>>
>>>   cleanup:
>>>       closesocket(fd);
>>> -    return ret;
>>> +    return;
>>>   }
>>>
>>>   /*
>>> diff --git a/block/snapshot.c b/block/snapshot.c
>>> index a05c0c0..3122e3c 100644
>>> --- a/block/snapshot.c
>>> +++ b/block/snapshot.c
>>> @@ -138,20 +138,27 @@ int bdrv_can_snapshot(BlockDriverState *bs)
>>>       return 1;
>>>   }
>>>
>>> -int bdrv_snapshot_create(BlockDriverState *bs,
>>> -                         QEMUSnapshotInfo *sn_info)
>>> +void bdrv_snapshot_create(BlockDriverState *bs,
>>> +                          QEMUSnapshotInfo *sn_info,
>>> +                          Error **errp)
>>>   {
>>>       BlockDriver *drv = bs->drv;
>>>       if (!drv) {
>>> -        return -ENOMEDIUM;
>>> +        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM,
>>> bdrv_get_device_name(bs));
>>> +        return;
>>>       }
>>>       if (drv->bdrv_snapshot_create) {
>>> -        return drv->bdrv_snapshot_create(bs, sn_info);
>>> +        drv->bdrv_snapshot_create(bs, sn_info, errp);
>>> +        return;
>>>       }
>>>       if (bs->file) {
>>> -        return bdrv_snapshot_create(bs->file, sn_info);
>>> +        bdrv_snapshot_create(bs->file, sn_info, errp);
>>> +        return;
>>>       }
>>> -    return -ENOTSUP;
>>> +
>>> +    error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
>>> +              drv->format_name, bdrv_get_device_name(bs),
>>> +              "internal snapshot creation");
>>>   }
>>>
>>>   int bdrv_snapshot_goto(BlockDriverState *bs,
>>> diff --git a/blockdev.c b/blockdev.c
>>> index 4f76e28..c4e7124 100644
>>> --- a/blockdev.c
>>> +++ b/blockdev.c
>>> @@ -1077,7 +1077,7 @@ static void
>>> internal_snapshot_prepare(BlkTransactionState *common,
>>>       qemu_timeval tv;
>>>       BlockdevSnapshotInternal *internal;
>>>       InternalSnapshotState *state;
>>> -    int ret1;
>>> +    Error *local_err = NULL;
>>>
>>>       g_assert(common->action->kind ==
>>>               
>>> TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC);
>>> @@ -1135,11 +1135,9 @@ static void
>>> internal_snapshot_prepare(BlkTransactionState *common,
>>>       sn->date_nsec = tv.tv_usec * 1000;
>>>       sn->vm_clock_nsec = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>>>
>>> -    ret1 = bdrv_snapshot_create(bs, sn);
>>> -    if (ret1 < 0) {
>>> -        error_setg_errno(errp, -ret1,
>>> -                         "Failed to create snapshot '%s' on device
>>> '%s'",
>>> -                         name, device);
>>> +    bdrv_snapshot_create(bs, sn, &local_err);
>>> +    if (error_is_set(&local_err)) {
>>> +        error_propagate(errp, local_err);
>>>           return;
>>>       }
>>>
>>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>>> index a48731d..553d843 100644
>>> --- a/include/block/block_int.h
>>> +++ b/include/block/block_int.h
>>> @@ -161,8 +161,9 @@ struct BlockDriver {
>>>       int (*bdrv_write_compressed)(BlockDriverState *bs, int64_t
>>> sector_num,
>>>                                    const uint8_t *buf, int nb_sectors);
>>>
>>> -    int (*bdrv_snapshot_create)(BlockDriverState *bs,
>>> -                                QEMUSnapshotInfo *sn_info);
>>> +    void (*bdrv_snapshot_create)(BlockDriverState *bs,
>>> +                                 QEMUSnapshotInfo *sn_info,
>>> +                                 Error **errp);
>>>       int (*bdrv_snapshot_goto)(BlockDriverState *bs,
>>>                                 const char *snapshot_id);
>>>       int (*bdrv_snapshot_delete)(BlockDriverState *bs,
>>> diff --git a/include/block/snapshot.h b/include/block/snapshot.h
>>> index 012bf22..a998316 100644
>>> --- a/include/block/snapshot.h
>>> +++ b/include/block/snapshot.h
>>> @@ -47,8 +47,9 @@ bool
>>> bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
>>>                                          QEMUSnapshotInfo *sn_info,
>>>                                          Error **errp);
>>>   int bdrv_can_snapshot(BlockDriverState *bs);
>>> -int bdrv_snapshot_create(BlockDriverState *bs,
>>> -                         QEMUSnapshotInfo *sn_info);
>>> +void bdrv_snapshot_create(BlockDriverState *bs,
>>> +                          QEMUSnapshotInfo *sn_info,
>>> +                          Error **errp);
>>>   int bdrv_snapshot_goto(BlockDriverState *bs,
>>>                          const char *snapshot_id);
>>>   int bdrv_snapshot_delete(BlockDriverState *bs,
>>> diff --git a/qemu-img.c b/qemu-img.c
>>> index 926f0a0..aa8b46f 100644
>>> --- a/qemu-img.c
>>> +++ b/qemu-img.c
>>> @@ -2080,10 +2080,12 @@ static int img_snapshot(int argc, char **argv)
>>>           sn.date_sec = tv.tv_sec;
>>>           sn.date_nsec = tv.tv_usec * 1000;
>>>
>>> -        ret = bdrv_snapshot_create(bs, &sn);
>>> -        if (ret) {
>>> -            error_report("Could not create snapshot '%s': %d (%s)",
>>> -                snapshot_name, ret, strerror(-ret));
>>> +        bdrv_snapshot_create(bs, &sn, &err);
>>> +        if (error_is_set(&err)) {
>>> +            error_report("Could not create snapshot '%s': %s",
>>> +                         snapshot_name, error_get_pretty(err));
>>> +            error_free(err);
>>> +            ret = 1;
>>>           }
>>>           break;
>>>
>>> diff --git a/savevm.c b/savevm.c
>>> index 2f631d4..617d6eb 100644
>>> --- a/savevm.c
>>> +++ b/savevm.c
>>> @@ -2366,6 +2366,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
>>>       qemu_timeval tv;
>>>       struct tm tm;
>>>       const char *name = qdict_get_try_str(qdict, "name");
>>> +    Error *err = NULL;
>>>
>>>       /* Verify if there is a device that doesn't support snapshots
>>> and is writable */
>>>       bs = NULL;
>>> @@ -2439,10 +2440,13 @@ void do_savevm(Monitor *mon, const QDict
>>> *qdict)
>>>           if (bdrv_can_snapshot(bs1)) {
>>>               /* Write VM state size only to the image that contains
>>> the state */
>>>               sn->vm_state_size = (bs == bs1 ? vm_state_size : 0);
>>> -            ret = bdrv_snapshot_create(bs1, sn);
>>> -            if (ret < 0) {
>>> -                monitor_printf(mon, "Error while creating snapshot
>>> on '%s'\n",
>>> -                               bdrv_get_device_name(bs1));
>>> +            bdrv_snapshot_create(bs1, sn, &err);
>>> +            if (error_is_set(&err)) {
>>> +                monitor_printf(mon,
>>> +                               "Error while creating snapshot on
>>> '%s': %s\n",
>>> +                               bdrv_get_device_name(bs1),
>>> +                               error_get_pretty(err));
>>> +                error_free(err);
>>>               }
>>>           }
>>>       }
>>
>