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Date: Mon, 2 Nov 2015 20:09:07 +0300
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Subject: Re: [Qemu-devel] [PATCH v7 13/35] hostmem-file: use whole file size
	if possible
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To: Xiao Guangrong <guangrong.xiao@linux.intel.com>, pbonzini@redhat.com, imammedo@redhat.com
Cc: ehabkost@redhat.com, kvm@vger.kernel.org, mst@redhat.com, gleb@kernel.org, mtosatti@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, dan.j.williams@intel.com, rth@twiddle.net

On 02.11.2015 12:13, Xiao Guangrong wrote:
> Use the whole file size if @size is not specified which is useful
> if we want to directly pass a file to guest
>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---
>   backends/hostmem-file.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> index 9097a57..ea355c1 100644
> --- a/backends/hostmem-file.c
> +++ b/backends/hostmem-file.c
> @@ -38,15 +38,29 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
>   {
>       HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
>   
> -    if (!backend->size) {
> -        error_setg(errp, "can't create backend with size 0");
> -        return;
> -    }
>       if (!fb->mem_path) {
>           error_setg(errp, "mem-path property not set");
>           return;
>       }
>   
> +    if (!backend->size) {
> +        Error *local_err = NULL;
> +
> +        /*
> +         * use the whole file size if @size is not specified.
> +         */
> +        backend->size = qemu_file_getlength(fb->mem_path, &local_err);
> +        if (local_err) {
> +            error_propagate(errp, local_err);
> +            return;
> +        }
> +    }
> +
> +    if (!backend->size) {
> +        error_setg(errp, "can't create backend on the file whose size is 0");
> +        return;
> +    }
> +
>       backend->force_prealloc = mem_prealloc;
>       memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
>                                    object_get_canonical_path(OBJECT(backend)),

why not just

+    if (!backend->size) {
+        /*
+         * use the whole file size if @size is not specified.
+         */
+        backend->size = qemu_file_getlength(fb->mem_path, errp);
+        if (*errp) {
+            return;
+        }
+    }


what the purpose of propagating?

-- 
Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.