[Qemu-devel] [PATCH v4 2/2] quorum: modify vote rules for flush operation

[Changlong Xie <xiecl.fnst@cn.fujitsu.com>]

Keep flush interface the same logic as quorum read/write, Otherwise in
following scenario, we'll encounter unexpected errors.

Quorum has two children(A, B). A do flush sucessfully, but B flush failed.
This cause the filesystem of guest 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 <wency@cn.fujitsu.com>
Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
---
 block/quorum.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/block/quorum.c b/block/quorum.c
index d3c3958..6048208 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -768,19 +768,28 @@ static coroutine_fn int quorum_co_flush(BlockDriverState *bs)
     QuorumVoteValue result_value;
     int i;
     int result = 0;
+    int success_count = 0;
 
     QLIST_INIT(&error_votes.vote_list);
     error_votes.compare = quorum_64bits_compare;
 
     for (i = 0; i < s->num_children; i++) {
         result = bdrv_co_flush(s->children[i]->bs);
-        result_value.l = result;
-        quorum_count_vote(&error_votes, &result_value, i);
+        if (result) {
+            quorum_flush_error(s->children[i]->bs->node_name, "Flush failed");
+            result_value.l = result;
+            quorum_count_vote(&error_votes, &result_value, i);
+        } else {
+            success_count++;
+        }
     }
 
-    winner = quorum_get_vote_winner(&error_votes);
-    result = winner->value.l;
-
+    if (success_count >= s->threshold) {
+        result = 0;
+    } else {
+        winner = quorum_get_vote_winner(&error_votes);
+        result = winner->value.l;
+    }
     quorum_free_vote_list(&error_votes);
 
     return result;
-- 
1.9.3