[v2,1/7] block/quorum.c: stable children names

Commit Message

Lukas Straub June 6, 2020, 7:17 p.m. UTC

If we remove the child with the highest index from the quorum,
decrement s->next_child_index. This way we get stable children
names as long as we only remove the last child.

Signed-off-by: Lukas Straub <[e-mail]>
Fixes: https://bugs.launchpad.net/bugs/1881231
Reviewed-by: Zhang Chen <[e-mail]>
Reviewed-by: Alberto Garcia <[e-mail]>
---
 block/quorum.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

--
2.20.1

Patch

diff --git a/block/quorum.c b/block/quorum.c
index 6d7a56bd93..acfa09c2cc 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -29,6 +29,8 @@ 

 #define HASH_LENGTH 32

+#define INDEXSTR_LEN 32
+
 #define QUORUM_OPT_VOTE_THRESHOLD "vote-threshold"
 #define QUORUM_OPT_BLKVERIFY      "blkverify"
 #define QUORUM_OPT_REWRITE        "rewrite-corrupted"
@@ -972,9 +974,9 @@  static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
     opened = g_new0(bool, s->num_children);

     for (i = 0; i < s->num_children; i++) {
-        char indexstr[32];
-        ret = snprintf(indexstr, 32, "children.%d", i);
-        assert(ret < 32);
+        char indexstr[INDEXSTR_LEN];
+        ret = snprintf(indexstr, INDEXSTR_LEN, "children.%d", i);
+        assert(ret < INDEXSTR_LEN);

         s->children[i] = bdrv_open_child(NULL, options, indexstr, bs,
                                          &child_format, false, &local_err);
@@ -1026,7 +1028,7 @@  static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs,
 {
     BDRVQuorumState *s = bs->opaque;
     BdrvChild *child;
-    char indexstr[32];
+    char indexstr[INDEXSTR_LEN];
     int ret;

     if (s->is_blkverify) {
@@ -1041,8 +1043,8 @@  static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs,
         return;
     }

-    ret = snprintf(indexstr, 32, "children.%u", s->next_child_index);
-    if (ret < 0 || ret >= 32) {
+    ret = snprintf(indexstr, INDEXSTR_LEN, "children.%u", s->next_child_index);
+    if (ret < 0 || ret >= INDEXSTR_LEN) {
         error_setg(errp, "cannot generate child name");
         return;
     }
@@ -1069,6 +1071,7 @@  static void quorum_del_child(BlockDriverState *bs, BdrvChild *child,
                              Error **errp)
 {
     BDRVQuorumState *s = bs->opaque;
+    char indexstr[INDEXSTR_LEN];
     int i;

     for (i = 0; i < s->num_children; i++) {
@@ -1090,6 +1093,11 @@  static void quorum_del_child(BlockDriverState *bs, BdrvChild *child,
     /* We know now that num_children > threshold, so blkverify must be false */
     assert(!s->is_blkverify);

+    snprintf(indexstr, INDEXSTR_LEN, "children.%u", s->next_child_index - 1);
+    if (!strncmp(child->name, indexstr, INDEXSTR_LEN)) {
+        s->next_child_index--;
+    }
+
     bdrv_drained_begin(bs);

     /* We can safely remove this child now */