qapi: introduce PreallocMode and new PreallocModes full and falloc.

This patch prepares for the subsequent patches.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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"
 
@@ -1738,7 +1739,7 @@ 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)
 {
@@ -1876,7 +1877,7 @@ static int qcow2_create2(const char *filename, int64_t total_size,
     }
 
     /* And if we're supposed to preallocate metadata, do that now */
-    if (prealloc) {
+    if (prealloc == PREALLOC_MODE_METADATA) {
         BDRVQcowState *s = bs->opaque;
         qemu_co_mutex_lock(&s->lock);
         ret = preallocate(bs);
@@ -1915,7 +1916,7 @@ 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;
     int version = 3;
     Error *local_err = NULL;
     int ret;
@@ -1931,12 +1932,11 @@ 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 = qapi_enum_parse(PreallocMode_lookup, buf,
-        prealloc = 0;
+                               PREALLOC_MODE_MAX, PREALLOC_MODE_OFF,
-    } else if (!strcmp(buf, "metadata")) {
+                               &local_err);
-        prealloc = 1;
+    if (local_err) {
-    } else {
+        error_propagate(errp, local_err);
-        error_setg(errp, "Invalid preallocation mode: '%s'", buf);
         ret = -EINVAL;
         goto finish;
     }
@@ -1958,7 +1958,15 @@ static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
         flags |= BLOCK_FLAG_LAZY_REFCOUNTS;
     }
 
-    if (backing_file && prealloc) {
+    if (prealloc != PREALLOC_MODE_OFF &&
+        prealloc != PREALLOC_MODE_METADATA) {
+        ret = -EINVAL;
+        error_setg(errp, "Unsupported preallocate mode: %s",
+                   PreallocMode_lookup[prealloc]);
+        goto finish;
+    }
+
+    if (backing_file && prealloc != PREALLOC_MODE_OFF) {
         error_setg(errp, "Backing file and preallocation cannot be used at "
                    "the same time");
         ret = -EINVAL;

qapi/block-core.json

@@ -1708,3 +1708,20 @@
             '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' ] }

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 ==