Re: [RFC PATCH 1/5] hw/block: blk_check_size_and_read_all should report backend name

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 11/16/20 11:42 AM, David Edmondson wrote:
> If there are problems examining or reading data from the block
> backend, the error messages should include an appropriate identifier
> to assist in diagnoses.
> 
> Signed-off-by: David Edmondson <david.edmondson@oracle.com>
> ---
>  hw/block/block.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/block/block.c b/hw/block/block.c
> index 1e34573da7..8b284e1f14 100644
> --- a/hw/block/block.c
> +++ b/hw/block/block.c
> @@ -20,9 +20,6 @@
>   * BDRV_REQUEST_MAX_BYTES.
>   * On success, return true.
>   * On failure, store an error through @errp and return false.
> - * Note that the error messages do not identify the block backend.
> - * TODO Since callers don't either, this can result in confusing
> - * errors.
>   * This function not intended for actual block devices, which read on
>   * demand.  It's for things like memory devices that (ab)use a block
>   * backend to provide persistence.
> @@ -32,17 +29,19 @@ bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
>  {
>      int64_t blk_len;
>      int ret;
> +    const char *name = blk_name(blk);
>  
>      blk_len = blk_getlength(blk);
>      if (blk_len < 0) {
>          error_setg_errno(errp, -blk_len,
> -                         "can't get size of block backend");
> +                         "can't get size of block backend %s",

Maybe '%s' to notice empty name?

> +                         name);
>          return false;
>      }
>      if (blk_len != size) {
>          error_setg(errp, "device requires %" HWADDR_PRIu " bytes, "
> -                   "block backend provides %" PRIu64 " bytes",
> -                   size, blk_len);
> +                   "block backend %s provides %" PRIu64 " bytes",
> +                   size, name, blk_len);
>          return false;
>      }
>  
> @@ -55,7 +54,8 @@ bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
>      assert(size <= BDRV_REQUEST_MAX_BYTES);
>      ret = blk_pread(blk, 0, buf, size);
>      if (ret < 0) {
> -        error_setg_errno(errp, -ret, "can't read block backend");
> +        error_setg_errno(errp, -ret, "can't read block backend %s",
> +                         name);
>          return false;
>      }
>      return true;
>