Re: [Qemu-devel] [PATCH] [RFC] Xen PV backend: Move call to bdrv_new from blk_init to blk_connect

[Alex Bligh]

Stefano,

--On 1 April 2013 16:44:05 +0100 Stefano Stabellini 
<address@hidden> wrote:

> > Note this patch is compile-tested only.
>
> I think the patch looks good, just a minor comment.

Thanks. I guess I ought to actually test it works then :-)

> > +    /* fill info
> > +     * Temporarily write zero sectors as we won't know file size until
> > +     * bdrv_new has been called. blk_connect corrects this.
> > +     */
> > +    xenstore_write_be_int(&blkdev->xendev, "feature-flush-cache", 1);
> > +    xenstore_write_be_int(&blkdev->xendev, "feature-persistent", 1);
> > +    xenstore_write_be_int(&blkdev->xendev, "info", info);
> > +    xenstore_write_be_int(&blkdev->xendev, "sector-size", BLOCK_SIZE);
> > +    xenstore_write_be_int(&blkdev->xendev, "sectors", 0);
> > +    return 0;
>
> There is no need to fill the sector-size and sectors info here, you can
> do it later in blk_connect.

My concern (not knowing how xenstore works) was the possibility of leaving
them as uninitialized values. I'm taking it that if I don't initialise
them, the key is just absent - correct?

I'll redo and move setting sector-size and sectors into blk_connect, and
then add a second commit which removes BDRV_O_NOCACHE. Oh, and test it ...

--
Alex Bligh