Re: [Qemu-devel] [PATCH for-2.6 1/7] block/vpc: fix VPC 'qemu-img create' regression

[Jeff Cody <jcody@redhat.com>]

On Tue, Mar 22, 2016 at 11:33:38PM -0400, Jeff Cody wrote:
> Commit 'b8f45cdf7827e39f9a1e6cc446f5972cc6144237' switched VPC
> over to using blk_pwrite() instead of bdrv_pwrite_sync().  The
> return value of bdrv_pwrite_sync() was always 0 for success, and
> create_dynamic_disk() in one instance checked for a non-zero return
> value to indicate error.  However, blk_pwrite() may return positive
> values for success.
> 
> This fails silently as well, since vpc_create() did not set errp
> in this failuer case.  Set errp in all instances in vpc_create().
> 
> Signed-off-by: Jeff Cody <jcody@redhat.com>

Ping on this series - ideally the whole series for 2.6, but this patch
in particular is needed for 2.6 to prevent a regression from 2.5 (QEMU
can no longer create VPC/VHD images without this patch).

> ---
>  block/vpc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/block/vpc.c b/block/vpc.c
> index 8435205..bc3d1c6 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -774,7 +774,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf,
>      num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
>  
>      ret = blk_pwrite(blk, offset, buf, HEADER_SIZE);
> -    if (ret) {
> +    if (ret < 0) {
>          goto fail;
>      }
>  
> @@ -873,6 +873,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
>          } else if (!strcmp(disk_type_param, "fixed")) {
>              disk_type = VHD_FIXED;
>          } else {
> +            error_setg(errp, "Invalid disk type, %s", disk_type_param);
>              ret = -EINVAL;
>              goto out;
>          }
> @@ -924,6 +925,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
>          total_sectors = total_size / BDRV_SECTOR_SIZE;
>          /* Allow a maximum disk size of approximately 2 TB */
>          if (total_sectors > VHD_MAX_SECTORS) {
> +            error_setg(errp, "Disk size is too large, max size is 2040 GiB");
>              ret = -EFBIG;
>              goto out;
>          }
> @@ -974,6 +976,9 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
>      } else {
>          ret = create_fixed_disk(blk, buf, total_size);
>      }
> +    if (ret < 0) {
> +        error_setg(errp, "Unable to create or write VHD header");
> +    }
>  
>  out:
>      blk_unref(blk);
> -- 
> 1.9.3
>