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Date: Wed, 13 Jan 2010 17:26:48 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 1/2] block: flush backing_hd in the right
	place
References: <20100112124923.GA19631@lst.de>
In-Reply-To: <20100112124923.GA19631@lst.de>
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To: Christoph Hellwig <hch@lst.de>
Cc: qemu-devel@nongnu.org

On 01/12/2010 06:49 AM, Christoph Hellwig wrote:
> The backing device is only modified from bdrv_commit.  So instead of
> flushing it every time bdrv_flush is called for the front-end device
> only flush it after we're written data to it in bdrv_commit.
>
> Signed-off-by: Christoph Hellwig<hch@lst.de>
>    

Applied.  Thanks.

Regards,

Anthony Liguori

> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c	2010-01-12 11:34:35.549024986 +0100
> +++ qemu/block.c	2010-01-12 11:43:28.965006129 +0100
> @@ -623,6 +623,12 @@ int bdrv_commit(BlockDriverState *bs)
>       if (drv->bdrv_make_empty)
>   	return drv->bdrv_make_empty(bs);
>
> +    /*
> +     * Make sure all data we wrote to the backing device is actually
> +     * stable on disk.
> +     */
> +    if (bs->backing_hd)
> +        bdrv_flush(bs->backing_hd);
>       return 0;
>   }
>
> @@ -1124,12 +1130,8 @@ const char *bdrv_get_device_name(BlockDr
>
>   void bdrv_flush(BlockDriverState *bs)
>   {
> -    if (!bs->drv)
> -        return;
> -    if (bs->drv->bdrv_flush)
> +    if (bs->drv&&  bs->drv->bdrv_flush)
>           bs->drv->bdrv_flush(bs);
> -    if (bs->backing_hd)
> -        bdrv_flush(bs->backing_hd);
>   }
>
>   void bdrv_flush_all(void)
> @@ -1806,11 +1808,6 @@ BlockDriverAIOCB *bdrv_aio_flush(BlockDr
>
>       if (!drv)
>           return NULL;
> -
> -    /*
> -     * Note that unlike bdrv_flush the driver is reponsible for flushing a
> -     * backing image if it exists.
> -     */
>       return drv->bdrv_aio_flush(bs, cb, opaque);
>   }
>
>
>
>
>