Re: [PATCH v2 1/1] block/crypto: better error message when creating too large files

[Maxim Levitsky <mlevitsk@redhat.com>]

On Mon, 2020-04-20 at 12:29 +0300, Maxim Levitsky wrote:
> Currently if you attampt to create too large file with luks you
> get the following error message:
> 
> Formatting 'test.luks', fmt=luks size=17592186044416 key-secret=sec0
> qemu-img: test.luks: Could not resize file: File too large
> 
> While for raw format the error message is
> qemu-img: test.img: The image size is too large for file format 'raw'
> 
> 
> The reason for this is that qemu-img checks for errono of the failure,
> and presents the later error when it is -EFBIG
> 
> However crypto generic code 'swallows' the errno and replaces it
> with -EIO.
> 
> As an attempt to make it better, we can make luks driver,
> detect -EFBIG and in this case present a better error message,
> which is what this patch does
> 
> The new error message is:
> 
> qemu-img: error creating test.luks: The requested file size is too large
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1534898
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  block/crypto.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index d577f89659..f9f5dc11a7 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -104,18 +104,35 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
>                                        Error **errp)
>  {
>      struct BlockCryptoCreateData *data = opaque;
> +    Error *local_err = NULL;
> +    int ret;
>  
>      if (data->size > INT64_MAX || headerlen > INT64_MAX - data->size) {
> -        error_setg(errp, "The requested file size is too large");
> -        return -EFBIG;
> +        ret = -EFBIG;
> +        goto error;
>      }
>  
>      /* User provided size should reflect amount of space made
>       * available to the guest, so we must take account of that
>       * which will be used by the crypto header
>       */
> -    return blk_truncate(data->blk, data->size + headerlen, false,
> -                        data->prealloc, errp);
> +    ret = blk_truncate(data->blk, data->size + headerlen, false,
> +                        data->prealloc, &local_err);
> +
> +    if (ret >= 0) {
> +        return ret;
> +    }
> +
> +error:
> +    if (ret == -EFBIG) {
> +        /* Replace the error message with a better one */
> +        error_free(local_err);
> +        error_setg(errp, "The requested file size is too large");
> +    } else {
> +        error_propagate(errp, local_err);
> +    }
> +
> +    return ret;
>  }
>  
>  
Could someone pick that patch now that the freeze is over?
Best regards,
	Maxim Levitsky