Re: [Qemu-block] [PATCH v3 3/3] block/stream: introduce a bottom node

[Alberto Garcia]

On Fri 05 Apr 2019 06:56:19 PM CEST, Andrey Shinkevich wrote:
> @@ -232,8 +232,13 @@ void stream_start(const char *job_id, BlockDriverState 
> *bs,
>      StreamBlockJob *s;
>      BlockDriverState *iter;
>      bool bs_read_only;
> +    BlockDriverState *bottom = NULL;
> +    int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
> +
> +    /* Find the bottom node that has the base as its backing image */
> +    bottom = bdrv_find_overlay(bs, base);

What happens if bs == base here ??

> +    /*
> +     * Block all intermediate nodes between bs and bottom (inclusive), 
> because
> +     * they will disappear from the chain after this operation. The streaming
> +     * job reads every block only once, assuming that it doesn't change, so
> +     * forbid writes and resizes.
> +     */
> +    for (iter = bs; iter != bottom; iter = backing_bs(iter)) {
> +        block_job_add_bdrv(&s->common, "intermediate node", backing_bs(iter),
> +                           0, basic_flags, &error_abort);
>      }

This stops when iter == bottom, so bottom is not actually blocked.

> diff --git a/block/trace-events b/block/trace-events
> index 7335a42..5366d45 100644
> --- a/block/trace-events
> +++ b/block/trace-events
> @@ -20,7 +20,7 @@ bdrv_co_copy_range_to(void *src, uint64_t src_offset, void 
> *dst, uint64_t dst_of
>  
>  # stream.c
>  stream_one_iteration(void *s, int64_t offset, uint64_t bytes, int 
> is_allocated) "s %p offset %" PRId64 " bytes %" PRIu64 " is_allocated %d"
> -stream_start(void *bs, void *base, void *s) "bs %p base %p s %p"
> +stream_start(void *bs, void *bottom, void *s) "bs %p bottom %p s %p"

Is this change still correct? We don't pass bottom anymore.

Berto