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

[Changlong Xie]

Before:
1) vote_count > max: winner = candidate, update max
2) vote_count <= max: do nothing
Current:
1) vote_count > max: winner = candidate, update max
2) vote_count = max: compare the value of winner with
candidate, if candidate->value.l == 0, winner = candidate,
else do nothing
3) vote_count < max: do nothing

Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
Signed-off-by: Changlong Xie <xiecl.f...@cn.fujitsu.com>
---
 block/quorum.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/block/quorum.c b/block/quorum.c
index a5ae4b8..e431ff4 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -446,7 +446,7 @@ 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;
@@ -455,6 +455,12 @@ 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 == true && candidate->vote_count == max
+            && candidate->value.l == 0) {
+            winner = candidate;
         }
     }
 
@@ -544,7 +550,7 @@ 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;
     }
 
@@ -609,7 +615,7 @@ 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) {
@@ -769,7 +775,7 @@ 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