[Qemu-stable] [PATCH for-2.6 1/2] blockdev: Fix regression with the default naming of throttling groups

[Alberto Garcia]

When I/O limits are set for a block device, the name of the throttling
group is taken from the BlockBackend if the user doesn't specify one.

Commit efaa7c4eeb7490c6f37f3 moved the naming of the BlockBackend in
blockdev_init() to the end of the function, after I/O limits are set.
The consequence is that the throttling group gets an empty name.

Signed-off-by: Alberto Garcia <address@hidden>
Reported-by: Stefan Hajnoczi <address@hidden>
Cc: Max Reitz <address@hidden>
Cc: address@hidden
---
 blockdev.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index f1f520a..260a6f5 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -481,6 +481,7 @@ static BlockBackend *blockdev_init(const char *file, QDict 
*bs_opts,
     const char *id;
     BlockdevDetectZeroesOptions detect_zeroes =
         BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
+    const char *blk_id;
     const char *throttling_group = NULL;
 
     /* Check common options by copying from bs_opts to opts, all other options
@@ -510,6 +511,8 @@ static BlockBackend *blockdev_init(const char *file, QDict 
*bs_opts,
 
     writethrough = !qemu_opt_get_bool(opts, BDRV_OPT_CACHE_WB, true);
 
+    blk_id = qemu_opts_id(opts);
+
     qdict_extract_subqdict(bs_opts, &interval_dict, "stats-intervals.");
     qdict_array_split(interval_dict, &interval_list);
 
@@ -579,7 +582,7 @@ static BlockBackend *blockdev_init(const char *file, QDict 
*bs_opts,
 
         if (throttle_enabled(&cfg)) {
             if (!throttling_group) {
-                throttling_group = blk_name(blk);
+                throttling_group = blk_id;
             }
             blk_rs->throttle_group = g_strdup(throttling_group);
             blk_rs->throttle_state = throttle_group_incref(throttling_group);
@@ -614,7 +617,7 @@ static BlockBackend *blockdev_init(const char *file, QDict 
*bs_opts,
         /* disk I/O throttling */
         if (throttle_enabled(&cfg)) {
             if (!throttling_group) {
-                throttling_group = blk_name(blk);
+                throttling_group = blk_id;
             }
             bdrv_io_limits_enable(bs, throttling_group);
             bdrv_set_io_limits(bs, &cfg);
@@ -636,7 +639,7 @@ static BlockBackend *blockdev_init(const char *file, QDict 
*bs_opts,
     blk_set_enable_write_cache(blk, !writethrough);
     blk_set_on_error(blk, on_read_error, on_write_error);
 
-    if (!monitor_add_blk(blk, qemu_opts_id(opts), errp)) {
+    if (!monitor_add_blk(blk, blk_id, errp)) {
         blk_unref(blk);
         blk = NULL;
         goto err_no_bs_opts;
-- 
2.8.1