[v12,4/6] qapi: introduce PreallocMode and a new PreallocMode full.

diff --git a/block/qcow2.c b/block/qcow2.c
index 05df4b9..cfba93b 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -30,6 +30,7 @@ 
 #include "qemu/error-report.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qbool.h"
+#include "qapi/util.h"
 #include "trace.h"
 #include "qemu/option_int.h"
 
@@ -1594,7 +1595,7 @@  static int preallocate(BlockDriverState *bs)
 
 static int qcow2_create2(const char *filename, int64_t total_size,
                          const char *backing_file, const char *backing_format,
-                         int flags, size_t cluster_size, int prealloc,
+                         int flags, size_t cluster_size, PreallocMode prealloc,
                          QemuOpts *opts, int version,
                          Error **errp)
 {
@@ -1771,7 +1772,7 @@  static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
     uint64_t size = 0;
     int flags = 0;
     size_t cluster_size = DEFAULT_CLUSTER_SIZE;
-    int prealloc = 0;
+    PreallocMode prealloc = PREALLOC_MODE_OFF;
     int version = 3;
     Error *local_err = NULL;
     int ret;
@@ -1787,12 +1788,11 @@  static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
     cluster_size = qemu_opt_get_size_del(opts, BLOCK_OPT_CLUSTER_SIZE,
                                          DEFAULT_CLUSTER_SIZE);
     buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
-    if (!buf || !strcmp(buf, "off")) {
-        prealloc = 0;
-    } else if (!strcmp(buf, "metadata")) {
-        prealloc = 1;
-    } else {
-        error_setg(errp, "Invalid preallocation mode: '%s'", buf);
+    prealloc = qapi_enum_parse(PreallocMode_lookup, buf,
+                               PREALLOC_MODE_MAX, PREALLOC_MODE_OFF,
+                               &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
         ret = -EINVAL;
         goto finish;
     }
diff --git a/qapi/block-core.json b/qapi/block-core.json
index e378653..78d804f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1643,3 +1643,20 @@ 
             'len'   : 'int',
             'offset': 'int',
             'speed' : 'int' } }
+
+# @PreallocMode
+#
+# Preallocation mode of QEMU image file
+#
+# @off: no preallocation
+# @metadata: preallocate only for metadata
+# @falloc: like @full preallocation but allocate disk space by
+#          posix_fallocate() rather than writing zeros.
+# @full: preallocate all data by writing zeros to device to ensure disk
+#        space is really available. @full preallocation also sets up
+#        metadata correctly.
+#
+# Since 2.2
+##
+{ 'enum': 'PreallocMode',
+  'data': [ 'off', 'metadata', 'falloc', 'full' ] }
diff --git a/tests/qemu-iotests/049.out b/tests/qemu-iotests/049.out
index 71ca44d..09ca0ae 100644
--- a/tests/qemu-iotests/049.out
+++ b/tests/qemu-iotests/049.out
@@ -179,7 +179,7 @@  qemu-img create -f qcow2 -o preallocation=metadata TEST_DIR/t.qcow2 64M
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 preallocation='metadata' lazy_refcounts=off 
 
 qemu-img create -f qcow2 -o preallocation=1234 TEST_DIR/t.qcow2 64M
-qemu-img: TEST_DIR/t.qcow2: Invalid preallocation mode: '1234'
+qemu-img: TEST_DIR/t.qcow2: invalid parameter value: 1234
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 preallocation='1234' lazy_refcounts=off 
 
 == Check encryption option ==