[Qemu-devel] [PATCH 16/21] block: learn to open a driver with a given opaque

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

If the block driver is given an opaque data, there is no need to
allocate a new one. This allows to pass an existing driver state to the
new driver.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 block.c | 48 +++++++++++++++++++++++++++++-------------------
 1 file changed, 29 insertions(+), 19 deletions(-)

diff --git a/block.c b/block.c
index 9e7632e..f154979 100644
--- a/block.c
+++ b/block.c
@@ -319,7 +319,7 @@ void bdrv_register(BlockDriver *bdrv)
 
 /* create a new block device (by default it is empty) */
 static BlockDriverState *bdrv_new_int(const char *device_name,
-    BlockDriverState *child)
+    BlockDriverState *child, void *opaque)
 {
     BlockDriverState *bs;
 
@@ -344,13 +344,14 @@ static BlockDriverState *bdrv_new_int(const char *device_name,
                     child->device_name);
         }
     }
+    bs->opaque = opaque;
 
     return bs;
 }
 
 BlockDriverState *bdrv_new(const char *device_name)
 {
-    return bdrv_new_int(device_name, NULL);
+    return bdrv_new_int(device_name, NULL, NULL);
 }
 
 void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify)
@@ -810,7 +811,9 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     }
 
     bs->drv = drv;
-    bs->opaque = g_malloc0(drv->instance_size);
+    if (bs->opaque == NULL) {
+        bs->opaque = g_malloc0(drv->instance_size);
+    }
 
     bs->enable_write_cache = !!(flags & BDRV_O_CACHE_WB);
 
@@ -864,7 +867,8 @@ free_and_fail:
 }
 
 static int bdrv_file_open_int(BlockDriverState **pbs, const char *filename,
-    QDict *options, int flags, BlockDriverState *child, Error **errp)
+    QDict *options, int flags, BlockDriverState *child, void *opaque,
+    Error **errp)
 {
     BlockDriverState *bs;
     BlockDriver *drv;
@@ -878,7 +882,7 @@ static int bdrv_file_open_int(BlockDriverState **pbs, const char *filename,
         options = qdict_new();
     }
 
-    bs = bdrv_new_int("", child);
+    bs = bdrv_new_int("", child, opaque);
     bs->options = options;
     options = qdict_clone_shallow(options);
 
@@ -975,18 +979,11 @@ fail:
 int bdrv_file_open(BlockDriverState **pbs, const char *filename,
                    QDict *options, int flags, Error **errp)
 {
-    return bdrv_file_open_int(pbs, filename, options, flags, NULL, errp);
+    return bdrv_file_open_int(pbs, filename, options, flags, NULL, NULL, errp);
 }
 
-/*
- * Opens the backing file for a BlockDriverState if not yet open
- *
- * options is a QDict of options to pass to the block drivers, or NULL for an
- * empty set of options. The reference to the QDict is transferred to this
- * function (even on failure), so if the caller intends to reuse the dictionary,
- * it needs to use QINCREF() before calling bdrv_file_open.
- */
-int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
+static int bdrv_open_backing_file_int(BlockDriverState *bs,
+    QDict *options, void *opaque, Error **errp)
 {
     char backing_filename[PATH_MAX];
     int back_flags, ret;
@@ -1014,7 +1011,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
                                        sizeof(backing_filename));
     }
 
-    bs->backing_hd = bdrv_new_int("", bs);
+    bs->backing_hd = bdrv_new_int("", bs, opaque);
     if (bs->backing_format[0] != '\0') {
         back_drv = bdrv_find_format(bs->backing_format);
     }
@@ -1038,6 +1035,19 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
     return 0;
 }
 
+/*
+ * Opens the backing file for a BlockDriverState if not yet open
+ *
+ * options is a QDict of options to pass to the block drivers, or NULL for an
+ * empty set of options. The reference to the QDict is transferred to this
+ * function (even on failure), so if the caller intends to reuse the dictionary,
+ * it needs to use QINCREF() before calling bdrv_file_open.
+ */
+int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
+{
+    return bdrv_open_backing_file_int(bs, options, NULL, errp);
+}
+
 static int make_snapshot(BlockDriverState *bs, int64_t total_size,
                          const char **pfilename, BlockDriver **pdrv,
                          Error **errp)
@@ -1145,7 +1155,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
         }
 
         if (total_size == -1) {
-            bs1 = bdrv_new_int("", NULL);
+            bs1 = bdrv_new_int("", NULL, NULL);
             ret = bdrv_open(bs1, filename, NULL, 0, drv, &local_err);
             if (ret < 0) {
                 bdrv_unref(bs1);
@@ -1171,7 +1181,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
 
     ret = bdrv_file_open_int(&file, filename, file_options,
                              bdrv_open_flags(bs, flags | BDRV_O_UNMAP),
-                             bs, &local_err);
+                             bs, NULL, &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -1207,7 +1217,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
         QDict *backing_options;
 
         qdict_extract_subqdict(options, &backing_options, "backing.");
-        ret = bdrv_open_backing_file(bs, backing_options, &local_err);
+        ret = bdrv_open_backing_file_int(bs, backing_options, NULL, &local_err);
         if (ret < 0) {
             goto close_and_fail;
         }
-- 
1.8.3.1