Re: [Qemu-devel] [RFC PATCH 2/4] block: add live block commit functionality

[Eric Blake]

On 07/30/2012 11:16 PM, Jeff Cody wrote:
> This adds the live commit coroutine.  This iteration focuses on the
> commit only below the active layer, and not the active layer itself.
> 
> The behaviour is similar to block streaming; the sectors are walked
> through, and anything that exists above 'base' is committed back down
> into base.  At the end, intermediate images are deleted, and the
> chain stiched together.  Images are restored to their original open

s/stiched/stitched/

> +
> +enum {
> +    /*
> +     * Size of data buffer for populating the image file.  This should be 
> large
> +     * enough to process multiple clusters in a single call, so that 
> populating
> +     * contiguous regions of the image is efficient.
> +     */
> +    COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
> +};

Paolo's latest round of patches got to the point of making this
configurable for drive-mirror; is that something you should be copying here?

> +++ b/block_int.h
> @@ -342,4 +342,23 @@ void mirror_start(BlockDriverState *bs, BlockDriverState 
> *target,
>                    BlockDriverCompletionFunc *cb,
>                    void *opaque, Error **errp);
>  
> +/**
> + * commit_start:
> + * @bs: Top Block device
> + * @base: Block device that will be written into, and become the new top
> + * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
> + * @on_error: The action to take upon error.

Do we need to distinguish between rerror and werror?

> + * @cb: Completion function for the job.
> + * @opaque: Opaque pointer value passed to @cb.
> + * @orig_base_flags: The original open flags for the base image
> + * @orig_top_flags: The original open flags for the top image
> + * @errp: Error object.
> + *
> + */
> +void commit_start(BlockDriverState *bs, BlockDriverState *base,
> +                 BlockDriverState *top, int64_t speed,
> +                 BlockdevOnError on_error, BlockDriverCompletionFunc *cb,
> +                 void *opaque, int orig_base_flags, int orig_top_flags,
> +                 Error **errp);
> +
>  #endif /* BLOCK_INT_H */

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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