blockdev: Split monitor reference from BB creation

Before this patch, blk_new() automatically assigned a name to the new
BlockBackend and considered it referenced by the monitor. This patch
removes the implicit monitor_add_blk() call from blk_new() (and
consequently the monitor_remove_blk() call from blk_delete(), too) and
thus blk_new() (and related functions) no longer take a BB name
argument.

In fact, there is only a single point where blk_new()/blk_new_open() is
called and the new BB is monitor-owned, and that is in blockdev_init().
Besides thus relieving us from having to invent names for all of the BBs
we use in qemu-img, this fixes a bug where qemu cannot create a new
image if there already is a monitor-owned BB named "image".

If a BB and its BDS tree are created in a single operation, as of this
patch the BDS tree will be created before the BB is given a name
(whereas it was the other way around before). This results in minor
change to the output of iotest 087, whose reference output is amended
accordingly.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

10 files changed, 21 insertions, 33 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index a5b950c771..9ed39121b5 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -80,13 +80,11 @@ static QTAILQ_HEAD(, BlockBackend) monitor_block_backends =
     QTAILQ_HEAD_INITIALIZER(monitor_block_backends);
 
 /*
- * Create a new BlockBackend with @name, with a reference count of one.
- * @name must not be null or empty.
- * Fail if a BlockBackend with this name already exists.
+ * Create a new BlockBackend with a reference count of one.
  * Store an error through @errp on failure, unless it's null.
  * Return the new BlockBackend on success, null on failure.
  */
-BlockBackend *blk_new(const char *name, Error **errp)
+BlockBackend *blk_new(Error **errp)
 {
     BlockBackend *blk;
 
@@ -94,14 +92,7 @@ BlockBackend *blk_new(const char *name, Error **errp)
     blk->refcnt = 1;
     notifier_list_init(&blk->remove_bs_notifiers);
     notifier_list_init(&blk->insert_bs_notifiers);
-
     QTAILQ_INSERT_TAIL(&block_backends, blk, link);
-
-    if (!monitor_add_blk(blk, name, errp)) {
-        blk_unref(blk);
-        return NULL;
-    }
-
     return blk;
 }
 
@@ -109,12 +100,12 @@ BlockBackend *blk_new(const char *name, Error **errp)
  * Create a new BlockBackend with a new BlockDriverState attached.
  * Otherwise just like blk_new(), which see.
  */
-BlockBackend *blk_new_with_bs(const char *name, Error **errp)
+BlockBackend *blk_new_with_bs(Error **errp)
 {
     BlockBackend *blk;
     BlockDriverState *bs;
 
-    blk = blk_new(name, errp);
+    blk = blk_new(errp);
     if (!blk) {
         return NULL;
     }
@@ -137,14 +128,13 @@ BlockBackend *blk_new_with_bs(const char *name, Error **errp)
  * though, so callers of this function have to be able to specify @filename and
  * @flags.
  */
-BlockBackend *blk_new_open(const char *name, const char *filename,
-                           const char *reference, QDict *options, int flags,
-                           Error **errp)
+BlockBackend *blk_new_open(const char *filename, const char *reference,
+                           QDict *options, int flags, Error **errp)
 {
     BlockBackend *blk;
     int ret;
 
-    blk = blk_new_with_bs(name, errp);
+    blk = blk_new_with_bs(errp);
     if (!blk) {
         QDECREF(options);
         return NULL;
@@ -161,8 +151,6 @@ BlockBackend *blk_new_open(const char *name, const char *filename,
 
 static void blk_delete(BlockBackend *blk)
 {
-    monitor_remove_blk(blk);
-
     assert(!blk->refcnt);
     assert(!blk->name);
     assert(!blk->dev);
diff --git a/block/parallels.c b/block/parallels.c
index 0d1a60c972..b322d05c08 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -478,7 +478,7 @@ static int parallels_create(const char *filename, QemuOpts *opts, Error **errp)
         return ret;
     }
 
-    file = blk_new_open("image", filename, NULL, NULL,
+    file = blk_new_open(filename, NULL, NULL,
                         BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                         &local_err);
     if (file == NULL) {
diff --git a/block/qcow.c b/block/qcow.c
index c09cb7989a..73cf8a7081 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -793,7 +793,7 @@ static int qcow_create(const char *filename, QemuOpts *opts, Error **errp)
         goto cleanup;
     }
 
-    qcow_blk = blk_new_open("image", filename, NULL, NULL,
+    qcow_blk = blk_new_open(filename, NULL, NULL,
                             BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                             &local_err);
     if (qcow_blk == NULL) {
diff --git a/block/qcow2.c b/block/qcow2.c
index 3fd664b9ca..5f4fea6a55 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2159,7 +2159,7 @@ static int qcow2_create2(const char *filename, int64_t total_size,
         return ret;
     }
 
-    blk = blk_new_open("image", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {
@@ -2224,7 +2224,7 @@ static int qcow2_create2(const char *filename, int64_t total_size,
      */
     options = qdict_new();
     qdict_put(options, "driver", qstring_from_str("qcow2"));
-    blk = blk_new_open("image-qcow2", filename, NULL, options,
+    blk = blk_new_open(filename, NULL, options,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
                        &local_err);
     if (blk == NULL) {
@@ -2286,7 +2286,7 @@ static int qcow2_create2(const char *filename, int64_t total_size,
     /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
     options = qdict_new();
     qdict_put(options, "driver", qstring_from_str("qcow2"));
-    blk = blk_new_open("image-flush", filename, NULL, options,
+    blk = blk_new_open(filename, NULL, options,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
                        &local_err);
     if (blk == NULL) {
diff --git a/block/qed.c b/block/qed.c
index 225c6a5a80..5b24a9783f 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -574,7 +574,7 @@ static int qed_create(const char *filename, uint32_t cluster_size,
         return ret;
     }
 
-    blk = blk_new_open("image", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 06ae3bac62..a3aeae4a67 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1646,7 +1646,7 @@ static int sd_prealloc(const char *filename, Error **errp)
     void *buf = NULL;
     int ret;
 
-    blk = blk_new_open("image-prealloc", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        errp);
     if (blk == NULL) {
@@ -1843,7 +1843,7 @@ static int sd_create(const char *filename, QemuOpts *opts,
             goto out;
         }
 
-        blk = blk_new_open("backing", backing_file, NULL, NULL,
+        blk = blk_new_open(backing_file, NULL, NULL,
                            BDRV_O_PROTOCOL | BDRV_O_CACHE_WB, errp);
         if (blk == NULL) {
             ret = -EIO;
diff --git a/block/vdi.c b/block/vdi.c
index 662d14b74e..df9fa47db1 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -768,7 +768,7 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
         goto exit;
     }
 
-    blk = blk_new_open("image", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {
diff --git a/block/vhdx.c b/block/vhdx.c
index e15020c9be..78fe56ca04 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1838,7 +1838,7 @@ static int vhdx_create(const char *filename, QemuOpts *opts, Error **errp)
         goto exit;
     }
 
-    blk = blk_new_open("image", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {
diff --git a/block/vmdk.c b/block/vmdk.c
index 2f8e6cf1c8..80f033835e 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1661,7 +1661,7 @@ static int vmdk_create_extent(const char *filename, int64_t filesize,
         goto exit;
     }
 
-    blk = blk_new_open("extent", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {
@@ -1946,7 +1946,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
             goto exit;
         }
 
-        blk = blk_new_open("backing", full_backing, NULL, NULL,
+        blk = blk_new_open(full_backing, NULL, NULL,
                            BDRV_O_NO_BACKING | BDRV_O_CACHE_WB, errp);
         g_free(full_backing);
         if (blk == NULL) {
@@ -2018,7 +2018,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
         }
     }
 
-    new_blk = blk_new_open("descriptor", filename, NULL, NULL,
+    new_blk = blk_new_open(filename, NULL, NULL,
                            BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                            &local_err);
     if (new_blk == NULL) {
diff --git a/block/vpc.c b/block/vpc.c
index 0d1524d6f6..8435205a0c 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -888,7 +888,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         goto out;
     }
 
-    blk = blk_new_open("image", filename, NULL, NULL,
+    blk = blk_new_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                        &local_err);
     if (blk == NULL) {