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>

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.
+ * Create a new BlockBackend with a reference count of one.
- * @name must not be null or empty.
- * Fail if a BlockBackend with this name already exists.
  * 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,
+BlockBackend *blk_new_open(const char *filename, const char *reference,
-                           const char *reference, QDict *options, int flags,
+                           QDict *options, int flags, Error **errp)
-                           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);

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) {

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) {

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) {

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) {

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;

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) {

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) {

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) {

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) {

blockdev.c

@@ -147,6 +147,7 @@ void blockdev_auto_del(BlockBackend *blk)
     DriveInfo *dinfo = blk_legacy_dinfo(blk);
 
     if (dinfo && dinfo->auto_del) {
+        monitor_remove_blk(blk);
         blk_unref(blk);
     }
 }
@@ -561,7 +562,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
     if ((!file || !*file) && !qdict_size(bs_opts)) {
         BlockBackendRootState *blk_rs;
 
-        blk = blk_new(qemu_opts_id(opts), errp);
+        blk = blk_new(errp);
         if (!blk) {
             goto early_err;
         }
@@ -597,8 +598,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
             bdrv_flags |= BDRV_O_INACTIVE;
         }
 
-        blk = blk_new_open(qemu_opts_id(opts), file, NULL, bs_opts, bdrv_flags,
+        blk = blk_new_open(file, NULL, bs_opts, bdrv_flags, errp);
-                           errp);
         if (!blk) {
             goto err_no_bs_opts;
         }
@@ -630,6 +630,12 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
 
     blk_set_on_error(blk, on_read_error, on_write_error);
 
+    if (!monitor_add_blk(blk, qemu_opts_id(opts), errp)) {
+        blk_unref(blk);
+        blk = NULL;
+        goto err_no_bs_opts;
+    }
+
 err_no_bs_opts:
     qemu_opts_del(opts);
     QDECREF(interval_dict);
@@ -2859,6 +2865,8 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
         blk_remove_bs(blk);
     }
 
+    monitor_remove_blk(blk);
+
     /* if we have a device attached to this BlockDriverState
      * then we need to make the drive anonymous until the device
      * can be removed.  If this is a drive with no device backing
@@ -3976,6 +3984,7 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
 
     if (bs && bdrv_key_required(bs)) {
         if (blk) {
+            monitor_remove_blk(blk);
             blk_unref(blk);
         } else {
             QTAILQ_REMOVE(&monitor_bdrv_states, bs, monitor_list);
@@ -4005,6 +4014,7 @@ void qmp_x_blockdev_del(bool has_id, const char *id,
     }
 
     if (has_id) {
+        /* blk_by_name() never returns a BB that is not owned by the monitor */
         blk = blk_by_name(id);
         if (!blk) {
             error_setg(errp, "Cannot find block backend %s", id);
@@ -4052,6 +4062,7 @@ void qmp_x_blockdev_del(bool has_id, const char *id,
     }
 
     if (blk) {
+        monitor_remove_blk(blk);
         blk_unref(blk);
     } else {
         QTAILQ_REMOVE(&monitor_bdrv_states, bs, monitor_list);

device-hotplug.c

@@ -84,6 +84,8 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict)
 
 err:
     if (dinfo) {
-        blk_unref(blk_by_legacy_dinfo(dinfo));
+        BlockBackend *blk = blk_by_legacy_dinfo(dinfo);
+        monitor_remove_blk(blk);
+        blk_unref(blk);
     }
 }

hw/block/xen_disk.c

@@ -917,7 +917,7 @@ static int blk_connect(struct XenDevice *xendev)
 
         /* setup via xenbus -> create new block driver instance */
         xen_be_printf(&blkdev->xendev, 2, "create new bdrv (xenbus setup)\n");
-        blkdev->blk = blk_new_open(blkdev->dev, blkdev->filename, NULL, options,
+        blkdev->blk = blk_new_open(blkdev->filename, NULL, options,
                                    qflags, &local_err);
         if (!blkdev->blk) {
             xen_be_printf(&blkdev->xendev, 0, "error: %s\n",

include/sysemu/block-backend.h

@@ -59,11 +59,10 @@ typedef struct BlockDevOps {
     void (*resize_cb)(void *opaque);
 } BlockDevOps;
 
-BlockBackend *blk_new(const char *name, Error **errp);
+BlockBackend *blk_new(Error **errp);
-BlockBackend *blk_new_with_bs(const char *name, Error **errp);
+BlockBackend *blk_new_with_bs(Error **errp);
-BlockBackend *blk_new_open(const char *name, const char *filename,
+BlockBackend *blk_new_open(const char *filename, const char *reference,
-                           const char *reference, QDict *options, int flags,
+                           QDict *options, int flags, Error **errp);
-                           Error **errp);
 int blk_get_refcnt(BlockBackend *blk);
 void blk_ref(BlockBackend *blk);
 void blk_unref(BlockBackend *blk);

qemu-img.c

@@ -245,8 +245,7 @@ static int img_open_password(BlockBackend *blk, const char *filename,
 }
 
 
-static BlockBackend *img_open_opts(const char *id,
+static BlockBackend *img_open_opts(const char *optstr,
-                                   const char *optstr,
                                    QemuOpts *opts, int flags,
                                    bool require_io, bool quiet)
 {
@@ -254,7 +253,7 @@ static BlockBackend *img_open_opts(const char *id,
     Error *local_err = NULL;
     BlockBackend *blk;
     options = qemu_opts_to_qdict(opts, NULL);
-    blk = blk_new_open(id, NULL, NULL, options, flags, &local_err);
+    blk = blk_new_open(NULL, NULL, options, flags, &local_err);
     if (!blk) {
         error_reportf_err(local_err, "Could not open '%s'", optstr);
         return NULL;
@@ -267,7 +266,7 @@ static BlockBackend *img_open_opts(const char *id,
     return blk;
 }
 
-static BlockBackend *img_open_file(const char *id, const char *filename,
+static BlockBackend *img_open_file(const char *filename,
                                    const char *fmt, int flags,
                                    bool require_io, bool quiet)
 {
@@ -280,7 +279,7 @@ static BlockBackend *img_open_file(const char *id, const char *filename,
         qdict_put(options, "driver", qstring_from_str(fmt));
     }
 
-    blk = blk_new_open(id, filename, NULL, options, flags, &local_err);
+    blk = blk_new_open(filename, NULL, options, flags, &local_err);
     if (!blk) {
         error_reportf_err(local_err, "Could not open '%s': ", filename);
         return NULL;
@@ -294,8 +293,7 @@ static BlockBackend *img_open_file(const char *id, const char *filename,
 }
 
 
-static BlockBackend *img_open(const char *id,
+static BlockBackend *img_open(bool image_opts,
-                              bool image_opts,
                               const char *filename,
                               const char *fmt, int flags,
                               bool require_io, bool quiet)
@@ -312,9 +310,9 @@ static BlockBackend *img_open(const char *id,
         if (!opts) {
             return NULL;
         }
-        blk = img_open_opts(id, filename, opts, flags, true, quiet);
+        blk = img_open_opts(filename, opts, flags, true, quiet);
     } else {
-        blk = img_open_file(id, filename, fmt, flags, true, quiet);
+        blk = img_open_file(filename, fmt, flags, true, quiet);
     }
     return blk;
 }
@@ -686,7 +684,7 @@ static int img_check(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open("image", image_opts, filename, fmt, flags, true, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, true, quiet);
     if (!blk) {
         return 1;
     }
@@ -878,7 +876,7 @@ static int img_commit(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open("image", image_opts, filename, fmt, flags, true, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, true, quiet);
     if (!blk) {
         return 1;
     }
@@ -1212,13 +1210,13 @@ static int img_compare(int argc, char **argv)
         goto out3;
     }
 
-    blk1 = img_open("image_1", image_opts, filename1, fmt1, flags, true, quiet);
+    blk1 = img_open(image_opts, filename1, fmt1, flags, true, quiet);
     if (!blk1) {
         ret = 2;
         goto out3;
     }
 
-    blk2 = img_open("image_2", image_opts, filename2, fmt2, flags, true, quiet);
+    blk2 = img_open(image_opts, filename2, fmt2, flags, true, quiet);
     if (!blk2) {
         ret = 2;
         goto out2;
@@ -1899,11 +1897,8 @@ static int img_convert(int argc, char **argv)
 
     total_sectors = 0;
     for (bs_i = 0; bs_i < bs_n; bs_i++) {
-        char *id = bs_n > 1 ? g_strdup_printf("source_%d", bs_i)
+        blk[bs_i] = img_open(image_opts, argv[optind + bs_i],
-                            : g_strdup("source");
-        blk[bs_i] = img_open(id, image_opts, argv[optind + bs_i],
                              fmt, src_flags, true, quiet);
-        g_free(id);
         if (!blk[bs_i]) {
             ret = -1;
             goto out;
@@ -2048,8 +2043,7 @@ static int img_convert(int argc, char **argv)
      * the bdrv_create() call which takes different params.
      * Not critical right now, so fix can wait...
      */
-    out_blk = img_open_file("target", out_filename,
+    out_blk = img_open_file(out_filename, out_fmt, flags, true, quiet);
-                            out_fmt, flags, true, quiet);
     if (!out_blk) {
         ret = -1;
         goto out;
@@ -2240,7 +2234,7 @@ static ImageInfoList *collect_image_info_list(bool image_opts,
         }
         g_hash_table_insert(filenames, (gpointer)filename, NULL);
 
-        blk = img_open("image", image_opts, filename, fmt,
+        blk = img_open(image_opts, filename, fmt,
                        BDRV_O_FLAGS | BDRV_O_NO_BACKING,
                        false, false);
         if (!blk) {
@@ -2572,8 +2566,7 @@ static int img_map(int argc, char **argv)
         return 1;
     }
 
-    blk = img_open("image", image_opts, filename, fmt,
+    blk = img_open(image_opts, filename, fmt, BDRV_O_FLAGS, true, false);
-                   BDRV_O_FLAGS, true, false);
     if (!blk) {
         return 1;
     }
@@ -2718,8 +2711,7 @@ static int img_snapshot(int argc, char **argv)
     }
 
     /* Open the image */
-    blk = img_open("image", image_opts, filename, NULL,
+    blk = img_open(image_opts, filename, NULL, bdrv_oflags, true, quiet);
-                   bdrv_oflags, true, quiet);
     if (!blk) {
         return 1;
     }
@@ -2890,7 +2882,7 @@ static int img_rebase(int argc, char **argv)
      * Ignore the old backing file for unsafe rebase in case we want to correct
      * the reference to a renamed or moved backing file.
      */
-    blk = img_open("image", image_opts, filename, fmt, flags, true, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, true, quiet);
     if (!blk) {
         ret = -1;
         goto out;
@@ -2916,7 +2908,7 @@ static int img_rebase(int argc, char **argv)
         }
 
         bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));
-        blk_old_backing = blk_new_open("old_backing", backing_name, NULL,
+        blk_old_backing = blk_new_open(backing_name, NULL,
                                        options, src_flags, &local_err);
         if (!blk_old_backing) {
             error_reportf_err(local_err,
@@ -2933,7 +2925,7 @@ static int img_rebase(int argc, char **argv)
                 options = NULL;
             }
 
-            blk_new_backing = blk_new_open("new_backing", out_baseimg, NULL,
+            blk_new_backing = blk_new_open(out_baseimg, NULL,
                                            options, src_flags, &local_err);
             if (!blk_new_backing) {
                 error_reportf_err(local_err,
@@ -3227,7 +3219,7 @@ static int img_resize(int argc, char **argv)
     n = qemu_opt_get_size(param, BLOCK_OPT_SIZE, 0);
     qemu_opts_del(param);
 
-    blk = img_open("image", image_opts, filename, fmt,
+    blk = img_open(image_opts, filename, fmt,
                    BDRV_O_FLAGS | BDRV_O_RDWR, true, quiet);
     if (!blk) {
         ret = -1;
@@ -3387,7 +3379,7 @@ static int img_amend(int argc, char **argv)
         goto out;
     }
 
-    blk = img_open("image", image_opts, filename, fmt, flags, true, quiet);
+    blk = img_open(image_opts, filename, fmt, flags, true, quiet);
     if (!blk) {
         ret = -1;
         goto out;

qemu-io.c

@@ -61,7 +61,7 @@ static int openfile(char *name, int flags, QDict *opts)
         return 1;
     }
 
-    qemuio_blk = blk_new_open("hda", name, NULL, opts, flags, &local_err);
+    qemuio_blk = blk_new_open(name, NULL, opts, flags, &local_err);
     if (!qemuio_blk) {
         error_reportf_err(local_err, "can't open%s%s: ",
                           name ? " device " : "", name ?: "");

qemu-nbd.c

@@ -831,13 +831,13 @@ int main(int argc, char **argv)
         }
         options = qemu_opts_to_qdict(opts, NULL);
         qemu_opts_reset(&file_opts);
-        blk = blk_new_open("hda", NULL, NULL, options, flags, &local_err);
+        blk = blk_new_open(NULL, NULL, options, flags, &local_err);
     } else {
         if (fmt) {
             options = qdict_new();
             qdict_put(options, "driver", qstring_from_str(fmt));
         }
-        blk = blk_new_open("hda", srcpath, NULL, options, flags, &local_err);
+        blk = blk_new_open(srcpath, NULL, options, flags, &local_err);
     }
 
     if (!blk) {

tests/qemu-iotests/087.out

@@ -21,7 +21,7 @@ QMP_VERSION
 {"error": {"class": "GenericError", "desc": "Device name 'test-node' conflicts with an existing node name"}}
 {"error": {"class": "GenericError", "desc": "node-name=disk is conflicting with a device id"}}
 {"error": {"class": "GenericError", "desc": "Duplicate node name"}}
-{"error": {"class": "GenericError", "desc": "node-name=disk3 is conflicting with a device id"}}
+{"error": {"class": "GenericError", "desc": "Device name 'disk3' conflicts with an existing node name"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN"}