Re: [Qemu-devel] [PATCH 02/15] sheepdog: Fix error handling in sd_snapshot_delete()

[Kevin Wolf <kwolf@redhat.com>]

Am 02.03.2017 um 22:43 hat Markus Armbruster geschrieben:
> As a bdrv_snapshot_delete() method, sd_snapshot_delete() must set an
> error and return negative errno on failure.  It sometimes returns -1,
> and sometimes neglects to set an error.  It also prints error messages
> with error_report().  Fix all that.
> 
> Moreover, its handling of an attempt to delete an nonexistent snapshot
> is wrong: it error_report()s and succeeds.  Fix it to set an error and
> return -ENOENT instead.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

> -static bool remove_objects(BDRVSheepdogState *s)
> +static int remove_objects(BDRVSheepdogState *s, Error **errp)
>  {
>      int fd, i = 0, nr_objs = 0;
> -    Error *local_err = NULL;
>      int ret = 0;

Preexisting, but I'll mention it anyway: This style of initialising ret
with 0 isn't wrong, but it would be more obviously correct if you set
ret = 0 only immediately before the out: label. The way it is currently,
I had to assure myself that write_object() really can't return a
positive number.

> -    bool result = true;
>      SheepdogInode *inode = &s->inode;
>  
> -    fd = connect_to_sdog(s, &local_err);
> +    fd = connect_to_sdog(s, errp);
>      if (fd < 0) {
> -        error_report_err(local_err);
> -        return false;
> +        return fd;
>      }
>  
>      nr_objs = count_data_objs(inode);
> @@ -2447,15 +2444,14 @@ static bool remove_objects(BDRVSheepdogState *s)
>                                      data_vdi_id[start_idx]),
>                             false, s->cache_flags);
>          if (ret < 0) {
> -            error_report("failed to discard snapshot inode.");
> -            result = false;
> +            error_setg(errp, "failed to discard snapshot inode.");

As Eric said, remove the trailing period. I would also let the message
start with a capital letter for consistency with the other error
messages in sd_snapshot_delete().

>              goto out;
>          }
>      }
>  
>  out:
>      closesocket(fd);
> -    return result;
> +    return ret;
>  }
>  
>  static int sd_snapshot_delete(BlockDriverState *bs,
> @@ -2465,7 +2461,6 @@ static int sd_snapshot_delete(BlockDriverState *bs,
>  {
>      unsigned long snap_id = 0;
>      char snap_tag[SD_MAX_VDI_TAG_LEN];
> -    Error *local_err = NULL;
>      int fd, ret;
>      char buf[SD_MAX_VDI_LEN + SD_MAX_VDI_TAG_LEN];
>      BDRVSheepdogState *s = bs->opaque;
> @@ -2478,8 +2473,9 @@ static int sd_snapshot_delete(BlockDriverState *bs,
>      };
>      SheepdogVdiRsp *rsp = (SheepdogVdiRsp *)&hdr;
>  
> -    if (!remove_objects(s)) {
> -        return -1;
> +    ret = remove_objects(s, errp);
> +    if (ret) {
> +        return ret;
>      }
>  
>      memset(buf, 0, sizeof(buf));
> @@ -2500,35 +2496,36 @@ static int sd_snapshot_delete(BlockDriverState *bs,
>      }
>  
>      ret = find_vdi_name(s, s->name, snap_id, snap_tag, &vid, true,
> -                        &local_err);
> +                        errp);

This fits on a single line.

Nothing critical, but it seems you're going to send a new version
anyway, so you could as well improve it.

Kevin