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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 14 Oct 2016 21:29:02 +0200
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Subject: Re: [Qemu-devel] bug introduced by "block: Move throttling fields
 from BDS to BB"
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To: qemu-devel <qemu-devel@nongnu.org>, qemu block <qemu-block@nongnu.org>, Kevin Wolf <kwolf@redhat.com>, Alberto Garcia <berto@igalia.com>



On 14/10/2016 16:11, Paolo Bonzini wrote:
> -    ThrottleGroup *tg = container_of(blk_bs(blk)->throttle_state,
> -                                     ThrottleGroup, ts);
> +    BlockBackendPublic *blkp = blk_get_public(blk);
> +    ThrottleGroup *tg = container_of(blkp->throttle_state, ThrottleGroup, ts);
>      BlockBackend *token, *start;
>  
>      start = token = tg->tokens[is_write];
>  
>      /* get next bs round in round robin style */
>      token = throttle_group_next_blk(token);
> -    while (token != start && !blk_bs(token)->pending_reqs[is_write]) {
> +    while (token != start && !blkp->pending_reqs[is_write]) {
>          token = throttle_group_next_blk(token);
>      }
> 
> 
> blkp isn't updated every time token is updated.

BTW, the simplest fix is probably to introduce a function

static inline bool blk_has_pending_reqs(BlockBackend *blk,
                                        bool is_write)

Paolo