Re: [Qemu-devel] [PATCH v2 1/1] quorum: Change vote rules for 64 bits hash

[Dr. David Alan Gilbert]

* Changlong Xie (address@hidden) wrote:
> If quorum has two children(A, B). A do flush sucessfully, but B flush failed.
> We MUST choice A as winner rather than just pick anyone of them. Otherwise
> the filesystem of guest will become read-only with following errors:
> 
> end_request: I/O error, dev vda, sector 11159960
> Aborting journal on device vda3-8
> EXT4-fs error (device vda3): ext4_journal_start_sb:327: Detected abort journal
> EXT4-fs (vda3): Remounting filesystem read-only
> 
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: Changlong Xie <address@hidden>

Hi,
  That seems to fix the problem I was seeing; thanks.
(I don't know enough about the quorum layer to comment much more).

Dave

> ---
>  block/quorum.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/block/quorum.c b/block/quorum.c
> index 11cc60b..f094208 100644
> --- a/block/quorum.c
> +++ b/block/quorum.c
> @@ -447,7 +447,8 @@ static int quorum_compute_hash(QuorumAIOCB *acb, int i, 
> QuorumVoteValue *hash)
>      return 0;
>  }
>  
> -static QuorumVoteVersion *quorum_get_vote_winner(QuorumVotes *votes)
> +static QuorumVoteVersion *quorum_get_vote_winner(QuorumVotes *votes,
> +                                                 bool vote_error)
>  {
>      int max = 0;
>      QuorumVoteVersion *candidate, *winner = NULL;
> @@ -456,6 +457,12 @@ static QuorumVoteVersion 
> *quorum_get_vote_winner(QuorumVotes *votes)
>          if (candidate->vote_count > max) {
>              max = candidate->vote_count;
>              winner = candidate;
> +            continue;
> +        }
> +        /* For 64 bit hash */
> +        if (vote_error && candidate->vote_count == max
> +            && candidate->value.l == 0) {
> +            winner = candidate;
>          }
>      }
>  
> @@ -545,7 +552,7 @@ static int quorum_vote_error(QuorumAIOCB *acb)
>      }
>  
>      if (error) {
> -        winner = quorum_get_vote_winner(&error_votes);
> +        winner = quorum_get_vote_winner(&error_votes, false);
>          ret = winner->value.l;
>      }
>  
> @@ -610,7 +617,7 @@ static bool quorum_vote(QuorumAIOCB *acb)
>      }
>  
>      /* vote to select the most represented version */
> -    winner = quorum_get_vote_winner(&acb->votes);
> +    winner = quorum_get_vote_winner(&acb->votes, false);
>  
>      /* if the winner count is smaller than threshold the read fails */
>      if (winner->vote_count < s->threshold) {
> @@ -770,7 +777,7 @@ static coroutine_fn int quorum_co_flush(BlockDriverState 
> *bs)
>          quorum_count_vote(&error_votes, &result_value, i);
>      }
>  
> -    winner = quorum_get_vote_winner(&error_votes);
> +    winner = quorum_get_vote_winner(&error_votes, true);
>      result = winner->value.l;
>  
>      quorum_free_vote_list(&error_votes);
> -- 
> 1.9.3
> 
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK