block: saner flags filtering in bdrv_open2

Clean up the current mess about figuring out which flags to pass to the
driver.  BDRV_O_FILE, BDRV_O_SNAPSHOT and BDRV_O_NO_BACKING are flags
only used by the block layer internally so filter them out directly.
Previously BDRV_O_NO_BACKING could accidentally be passed to the drivers,
but wasn't ever used.

Signed-off-by: Christoph Hellwig <hch@lst.de>

ping?

On Thu, Jan 28, 2010 at 03:19:12PM +0100, Christoph Hellwig wrote:
> Clean up the current mess about figuring out which flags to pass to the
> driver.  BDRV_O_FILE, BDRV_O_SNAPSHOT and BDRV_O_NO_BACKING are flags
> only used by the block layer internally so filter them out directly.
> Previously BDRV_O_NO_BACKING could accidentally be passed to the drivers,
> but wasn't ever used.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c	2010-01-28 15:12:52.316024386 +0100
> +++ qemu/block.c	2010-01-28 15:13:33.419004083 +0100
> @@ -451,13 +451,20 @@ int bdrv_open2(BlockDriverState *bs, con
>          bs->enable_write_cache = 1;
>  
>      bs->read_only = (flags & BDRV_O_RDWR) == 0;
> -    if (!(flags & BDRV_O_FILE)) {
> -        open_flags = (flags & (BDRV_O_RDWR | BDRV_O_CACHE_MASK|BDRV_O_NATIVE_AIO));
> -        if (bs->is_temporary) { /* snapshot should be writeable */
> -            open_flags |= BDRV_O_RDWR;
> -        }
> -    } else {
> -        open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);
> +
> +    /*
> +     * Clear flags that are internal to the block layer before opening the
> +     * image.
> +     */
> +    open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
> +
> +    /*
> +     * Snapshots should be writeable.
> +     *
> +     * XXX(hch): and what is the point of a snapshot during a read-only open?
> +     */
> +    if (!(flags & BDRV_O_FILE) && bs->is_temporary) {
> +        open_flags |= BDRV_O_RDWR;
>      }
>  
>      ret = drv->bdrv_open(bs, filename, open_flags);
> 
---end quoted text---

On 01/28/2010 08:19 AM, Christoph Hellwig wrote:
> Clean up the current mess about figuring out which flags to pass to the
> driver.  BDRV_O_FILE, BDRV_O_SNAPSHOT and BDRV_O_NO_BACKING are flags
> only used by the block layer internally so filter them out directly.
> Previously BDRV_O_NO_BACKING could accidentally be passed to the drivers,
> but wasn't ever used.
>
> Signed-off-by: Christoph Hellwig<hch@lst.de>
>    

Applied.  Thanks.

Regards,

Anthony Liguori

> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c	2010-01-28 15:12:52.316024386 +0100
> +++ qemu/block.c	2010-01-28 15:13:33.419004083 +0100
> @@ -451,13 +451,20 @@ int bdrv_open2(BlockDriverState *bs, con
>           bs->enable_write_cache = 1;
>
>       bs->read_only = (flags&  BDRV_O_RDWR) == 0;
> -    if (!(flags&  BDRV_O_FILE)) {
> -        open_flags = (flags&  (BDRV_O_RDWR | BDRV_O_CACHE_MASK|BDRV_O_NATIVE_AIO));
> -        if (bs->is_temporary) { /* snapshot should be writeable */
> -            open_flags |= BDRV_O_RDWR;
> -        }
> -    } else {
> -        open_flags = flags&  ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);
> +
> +    /*
> +     * Clear flags that are internal to the block layer before opening the
> +     * image.
> +     */
> +    open_flags = flags&  ~(BDRV_O_FILE | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
> +
> +    /*
> +     * Snapshots should be writeable.
> +     *
> +     * XXX(hch): and what is the point of a snapshot during a read-only open?
> +     */
> +    if (!(flags&  BDRV_O_FILE)&&  bs->is_temporary) {
> +        open_flags |= BDRV_O_RDWR;
>       }
>
>       ret = drv->bdrv_open(bs, filename, open_flags);
>
>
>
>