Re: [Qemu-devel] [PATCH V10 09/13] quorum: Add quorum_co_get_block_status.

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Sunday 02 Feb 2014 à 22:44:07 (+0100), Max Reitz a écrit :
> On 28.01.2014 17:52, Benoît Canet wrote:
> >From: Benoît Canet <benoit@irqsave.net>
> >
> >Signed-off-by: Benoit Canet <benoit@irqsave.net>
> >---
> >  block/quorum.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 67 insertions(+)
> >
> >diff --git a/block/quorum.c b/block/quorum.c
> >index a47cd33..9b0718b 100644
> >--- a/block/quorum.c
> >+++ b/block/quorum.c
> >@@ -171,6 +171,22 @@ static int quorum_sha256_compare(QuorumVoteValue *a, QuorumVoteValue *b)
> >      return memcmp(a->h, b->h, HASH_LENGTH);
> >  }
> >+static int quorum_64bits_compare(QuorumVoteValue *a, QuorumVoteValue *b)
> >+{
> >+    int64_t i = a->l;
> >+    int64_t j = b->l;
> >+
> >+    if (i < j) {
> >+        return -1;
> >+    }
> >+
> >+    if (i > j) {
> >+        return 1;
> >+    }
> >+
> >+    return 0;
> >+}
> >+
> >  static QuorumAIOCB *quorum_aio_get(BDRVQuorumState *s,
> >                                     BlockDriverState *bs,
> >                                     QEMUIOVector *qiov,
> >@@ -587,6 +603,56 @@ static void quorum_invalidate_cache(BlockDriverState *bs)
> >      }
> >  }
> >+static int64_t coroutine_fn quorum_co_get_block_status(BlockDriverState *bs,
> >+                                                       int64_t sector_num,
> >+                                                       int nb_sectors,
> >+                                                       int *pnum)
> >+{
> >+    BDRVQuorumState *s = bs->opaque;
> >+    QuorumVoteVersion *winner = NULL;
> >+    QuorumVotes result_votes, num_votes;
> >+    QuorumVoteValue result_value, num_value;
> >+    int i, num;
> >+    int64_t result = 0;
> >+
> >+    QLIST_INIT(&result_votes.vote_list);
> >+    QLIST_INIT(&num_votes.vote_list);
> >+    result_votes.compare = quorum_64bits_compare;
> >+    num_votes.compare = quorum_64bits_compare;
> >+
> >+    for (i = 0; i < s->total; i++) {
> >+        result = bdrv_get_block_status(s->bs[i], sector_num, nb_sectors, &num);
> >+        /* skip failed requests */
> >+        if (result < 0) {
> >+            continue;
> >+        }
> >+        result_value.l = result & BDRV_BLOCK_DATA;
> >+        num_value.l = num;
> >+        quorum_count_vote(&result_votes, &result_value, i);
> >+        quorum_count_vote(&num_votes, &num_value, i);
> >+    }
> >+
> >+    winner = quorum_get_vote_winner(&result_votes);
> >+    result = winner->value.l;
> 
> Below, you're reading the winning value after checking whether it's
> corresponding votes exceeded the threshold. It doesn't matter in the
> end, but for the sake of uniformity, I'd do it the same way here
> (i.e., move this statement below the if block).
> 
> >+    if (winner->vote_count < s->threshold) {
> >+        result = -ERANGE;
> 
> Is there any specific reason why you're returning -ERANGE here and
> -EIO everywhere else (even in quorum_getlength())?

I probably though "It's a comparison so it return -ERANGE".
A bad reason so :(

> 
> Max
> 
> >+        goto free_exit;
> >+    }
> >+
> >+    winner = quorum_get_vote_winner(&num_votes);
> >+    if (winner->vote_count < s->threshold) {
> >+        result = -ERANGE;
> >+        goto free_exit;
> >+    }
> >+    *pnum = winner->value.l;
> >+
> >+free_exit:
> >+    quorum_free_vote_list(&result_votes);
> >+    quorum_free_vote_list(&num_votes);
> >+
> >+    return result;
> >+}
> >+
> >  static BlockDriver bdrv_quorum = {
> >      .format_name        = "quorum",
> >      .protocol_name      = "quorum",
> >@@ -598,6 +664,7 @@ static BlockDriver bdrv_quorum = {
> >      .bdrv_aio_readv     = quorum_aio_readv,
> >      .bdrv_aio_writev    = quorum_aio_writev,
> >      .bdrv_invalidate_cache = quorum_invalidate_cache,
> >+    .bdrv_co_get_block_status = quorum_co_get_block_status,
> >  };
> >  static void bdrv_quorum_init(void)
> 
>