Re: [PATCH for-5.0 v2 09/23] quorum: Add QuorumChild.to_be_replaced

[Vladimir Sementsov-Ogievskiy]

11.11.2019 19:02, Max Reitz wrote:
> We will need this to verify that Quorum can let one of its children be
> replaced without breaking anything else.
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>   block/quorum.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/block/quorum.c b/block/quorum.c
> index 59cd524502..3a824e77e3 100644
> --- a/block/quorum.c
> +++ b/block/quorum.c
> @@ -67,6 +67,13 @@ typedef struct QuorumVotes {
>   
>   typedef struct QuorumChild {
>       BdrvChild *child;
> +
> +    /*
> +     * If set, check whether this node can be replaced without any
> +     * other parent noticing: Unshare CONSISTENT_READ, and take the
> +     * WRITE permission.
> +     */
> +    bool to_be_replaced;
>   } QuorumChild;
>   
>   /* the following structure holds the state of one quorum instance */
> @@ -1128,6 +1135,16 @@ static void quorum_child_perm(BlockDriverState *bs, 
> BdrvChild *c,
>                                 uint64_t perm, uint64_t shared,
>                                 uint64_t *nperm, uint64_t *nshared)
>   {
> +    BDRVQuorumState *s = bs->opaque;
> +    int i;
> +

loop is still useless if c == NULL...

if (c) {

> +    for (i = 0; i < s->num_children; i++) {
> +        if (s->children[i].child == c) {
> +            break;
> +        }
> +    }


        assert(i < s->num_children);

}

> +
>       *nperm = perm & DEFAULT_PERM_PASSTHROUGH;
>   
>       /*
> @@ -1137,6 +1154,12 @@ static void quorum_child_perm(BlockDriverState *bs, 
> BdrvChild *c,
>       *nshared = (shared & (BLK_PERM_CONSISTENT_READ |
>                             BLK_PERM_WRITE_UNCHANGED))
>                | DEFAULT_PERM_UNCHANGED;
> +
> +    if (c && s->children[i].to_be_replaced) {
> +        /* Prepare for sudden data changes */
> +        *nperm |= BLK_PERM_WRITE;
> +        *nshared &= ~BLK_PERM_CONSISTENT_READ;
> +    }
>   }
>   
>   static const char *const quorum_strong_runtime_opts[] = {
> 

with or without "if (c)":

Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>


-- 
Best regards,
Vladimir