[Qemu-devel] [PATCH v6 2/4] quorum: implement bdrv_add_child() and bdrv_del_child()

[Wen Congyang <wency@cn.fujitsu.com>]

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
---
 block.c               |  6 +++---
 block/quorum.c        | 59 +++++++++++++++++++++++++++++++++++++++++++++++++--
 include/block/block.h |  3 +++
 3 files changed, 63 insertions(+), 5 deletions(-)

diff --git a/block.c b/block.c
index bcba22f..d96d2cc 100644
--- a/block.c
+++ b/block.c
@@ -1079,9 +1079,9 @@ static int bdrv_fill_options(QDict **options, const char **pfilename,
     return 0;
 }
 
-static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
-                                    BlockDriverState *child_bs,
-                                    const BdrvChildRole *child_role)
+BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
+                             BlockDriverState *child_bs,
+                             const BdrvChildRole *child_role)
 {
     BdrvChild *child = g_new(BdrvChild, 1);
     *child = (BdrvChild) {
diff --git a/block/quorum.c b/block/quorum.c
index c4cda32..a9e499c 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -875,9 +875,9 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
         ret = -EINVAL;
         goto exit;
     }
-    if (s->num_children < 2) {
+    if (s->num_children < 1) {
         error_setg(&local_err,
-                   "Number of provided children must be greater than 1");
+                   "Number of provided children must be 1 or more");
         ret = -EINVAL;
         goto exit;
     }
@@ -997,6 +997,58 @@ static void quorum_attach_aio_context(BlockDriverState *bs,
     }
 }
 
+static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs,
+                             Error **errp)
+{
+    BDRVQuorumState *s = bs->opaque;
+    BdrvChild *child;
+
+    bdrv_drain(bs);
+
+    assert(s->num_children <= INT_MAX / sizeof(BdrvChild *));
+    if (s->num_children == INT_MAX / sizeof(BdrvChild *)) {
+        error_setg(errp, "Too many children");
+        return;
+    }
+    s->children = g_renew(BdrvChild *, s->children, s->num_children + 1);
+
+    bdrv_ref(child_bs);
+    child = bdrv_attach_child(bs, child_bs, &child_format);
+    s->children[s->num_children++] = child;
+}
+
+static void quorum_del_child(BlockDriverState *bs, BlockDriverState *child_bs,
+                             Error **errp)
+{
+    BDRVQuorumState *s = bs->opaque;
+    BdrvChild *child;
+    int i;
+
+    for (i = 0; i < s->num_children; i++) {
+        if (s->children[i]->bs == child_bs) {
+            break;
+        }
+    }
+
+    /* we have checked it in bdrv_del_child() */
+    assert(i < s->num_children);
+    child = s->children[i];
+
+    if (s->num_children <= s->threshold) {
+        error_setg(errp,
+            "The number of children cannot be lower than the vote threshold %d",
+            s->threshold);
+        return;
+    }
+
+    bdrv_drain(bs);
+    /* We can safely remove this child now */
+    memmove(&s->children[i], &s->children[i + 1],
+            (s->num_children - i - 1) * sizeof(void *));
+    s->children = g_renew(BdrvChild *, s->children, --s->num_children);
+    bdrv_unref_child(bs, child);
+}
+
 static void quorum_refresh_filename(BlockDriverState *bs)
 {
     BDRVQuorumState *s = bs->opaque;
@@ -1052,6 +1104,9 @@ static BlockDriver bdrv_quorum = {
     .bdrv_detach_aio_context            = quorum_detach_aio_context,
     .bdrv_attach_aio_context            = quorum_attach_aio_context,
 
+    .bdrv_add_child                     = quorum_add_child,
+    .bdrv_del_child                     = quorum_del_child,
+
     .is_filter                          = true,
     .bdrv_recurse_is_first_non_filter   = quorum_recurse_is_first_non_filter,
 };
diff --git a/include/block/block.h b/include/block/block.h
index ef84c87..f5bfb6b 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -516,6 +516,9 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs);
 void bdrv_ref(BlockDriverState *bs);
 void bdrv_unref(BlockDriverState *bs);
 void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child);
+BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
+                             BlockDriverState *child_bs,
+                             const BdrvChildRole *child_role);
 
 bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp);
 void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
-- 
2.4.3