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[Qemu-devel] [PATCH v3 7/8] add mirroring to transaction
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH v3 7/8] add mirroring to transaction |
Date: |
Mon, 5 Mar 2012 18:34:01 +0100 |
With it comes a new image creation mode, "no-backing-file", that can
be used to stream an image so that the destination does not need the
original image's backing file(s).
Both bdrv_append and blkmirror will set the backing_hd on the target,
even if the image is created without one, so that both streaming and
copy-on-write work properly (at least with qcow2 or qed, not raw).
Streaming mode works with the following gotchas:
- streaming will rewrite every bit of the source image;
- zero writes are not supported by the blkmirror driver, hence both
the source and the destination image will grow to full size.
Signed-off-by: Paolo Bonzini <address@hidden>
---
blockdev.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
qapi-schema.json | 21 +++++++++++++++++++--
qmp-commands.hx | 12 +++++++++++-
3 files changed, 73 insertions(+), 13 deletions(-)
diff --git a/blockdev.c b/blockdev.c
index 06c3017..df086d1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -689,6 +689,7 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
int ret = 0;
BlockdevActionList *dev_entry = dev_list;
BlkTransactionStates *states;
+ char *new_source = NULL;
QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionStates) snap_bdrv_states;
QSIMPLEQ_INIT(&snap_bdrv_states);
@@ -700,7 +701,8 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
while (NULL != dev_entry) {
BlockdevAction *dev_info = NULL;
BlockDriver *proto_drv;
- BlockDriver *drv;
+ BlockDriver *target_drv;
+ BlockDriver *drv = NULL;
int flags;
enum NewImageMode mode;
const char *new_image_file;
@@ -724,16 +726,36 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
format = dev_info->blockdev_snapshot_sync->format;
}
mode = dev_info->blockdev_snapshot_sync->mode;
+ new_source = g_strdup(new_image_file);
break;
+
+ case BLOCKDEV_ACTION_KIND_DRIVE_MIRROR:
+ device = dev_info->drive_mirror->device;
+ drv = bdrv_find_format("blkmirror");
+ if (!dev_info->drive_mirror->has_mode) {
+ dev_info->drive_mirror->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
+ }
+ new_image_file = dev_info->drive_mirror->target;
+ if (dev_info->drive_mirror->has_format) {
+ format = dev_info->drive_mirror->format;
+ }
+ mode = dev_info->drive_mirror->mode;
+ new_source = g_strdup_printf("blkmirror:%s:%s", format,
+ dev_info->drive_mirror->target);
+ break;
+
default:
abort();
}
- drv = bdrv_find_format(format);
- if (!drv) {
+ target_drv = bdrv_find_format(format);
+ if (!target_drv) {
error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
goto delete_and_fail;
}
+ if (!drv) {
+ drv = target_drv;
+ }
states->old_bs = bdrv_find(device);
if (!states->old_bs) {
@@ -757,7 +779,7 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
flags = states->old_bs->open_flags;
- proto_drv = bdrv_find_protocol(new_image_file);
+ proto_drv = bdrv_find_protocol(new_source);
if (!proto_drv) {
error_set(errp, QERR_INVALID_BLOCK_FORMAT, format);
goto delete_and_fail;
@@ -765,10 +787,18 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
/* create new image w/backing file */
if (mode != NEW_IMAGE_MODE_EXISTING) {
- ret = bdrv_img_create(new_image_file, format,
- states->old_bs->filename,
- states->old_bs->drv->format_name,
- NULL, -1, flags);
+ if (mode == NEW_IMAGE_MODE_ABSOLUTE_PATHS) {
+ ret = bdrv_img_create(new_image_file, format,
+ states->old_bs->filename,
+ states->old_bs->drv->format_name,
+ NULL, -1, flags);
+ } else {
+ uint64_t size;
+ bdrv_get_geometry(states->old_bs, &size);
+ size *= 512;
+ ret = bdrv_img_create(new_image_file, format,
+ NULL, NULL, NULL, size, flags);
+ }
if (ret) {
error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
goto delete_and_fail;
@@ -777,12 +807,14 @@ void qmp_transaction(BlockdevActionList *dev_list, Error
**errp)
/* We will manually add the backing_hd field to the bs later */
states->new_bs = bdrv_new("");
- ret = bdrv_open(states->new_bs, new_image_file,
+ ret = bdrv_open(states->new_bs, new_source,
flags | BDRV_O_NO_BACKING, drv);
if (ret != 0) {
- error_set(errp, QERR_OPEN_FILE_FAILED, new_image_file);
+ error_set(errp, QERR_OPEN_FILE_FAILED, new_source);
goto delete_and_fail;
}
+ g_free(new_source);
+ new_source = NULL;
}
@@ -810,6 +842,7 @@ exit:
QSIMPLEQ_FOREACH(states, &snap_bdrv_states, entry) {
g_free(states);
}
+ g_free(new_source);
return;
}
diff --git a/qapi-schema.json b/qapi-schema.json
index 0d24240..a61e90c 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1133,7 +1133,7 @@
# Since: 1.1
##
{ 'enum': 'NewImageMode'
- 'data': [ 'existing', 'absolute-paths' ] }
+ 'data': [ 'existing', 'absolute-paths', 'no-backing-file' ] }
##
# @BlockdevSnapshot
@@ -1152,6 +1152,23 @@
'*mode': 'NewImageMode' } }
##
+# @BlockdevMirror
+#
+# @device: the name of the device to start mirroring.
+#
+# @target: the image that will start receiving writes for @device. A new
+# file will be created unless @mode is "existing".
+#
+# @format: #optional the format of the target image, default is 'qcow2'.
+#
+# @mode: #optional whether and how QEMU should create a new image, default is
+# 'absolute-paths'.
+##
+{ 'type': 'BlockdevMirror',
+ 'data': { 'device': 'str', 'target': 'str', '*format': 'str',
+ '*mode': 'NewImageMode' } }
+
+##
# @BlockdevAction
#
# A discriminated record of operations that can be performed with
@@ -1159,7 +1175,8 @@
##
{ 'union': 'BlockdevAction',
'data': {
- 'blockdev-snapshot-sync': 'BlockdevSnapshot'
+ 'blockdev-snapshot-sync': 'BlockdevSnapshot',
+ 'drive-mirror': 'BlockdevMirror',
} }
##
diff --git a/qmp-commands.hx b/qmp-commands.hx
index dfe8a5b..9dcafd4 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -701,12 +701,16 @@ operation for now is snapshotting. If there is any
failure performing
transaction
-----------
-Atomically operate on one or more block devices. The only supported
-operation for now is snapshotting. If there is any failure performing
+Atomically operate on one or more block devices, snapshotting them
+or enabling mirrored writes. If there is any failure performing
any of the operations, all snapshots for the group are abandoned, and
the original disks pre-snapshot attempt are used.
+Mirrored writes keep the previous image file open, and start writing
+data also to the new file specified in the command.
+
A list of dictionaries is accepted, that contains the actions to be performed.
+
For snapshots this is the device, the file to use for the new snapshot,
and the format. The default format, if not specified, is qcow2.
@@ -716,7 +720,7 @@ Arguments:
actions array:
- "type": the operation to perform. The only supported
- value is "blockdev-snapshot-sync". (json-string)
+ values are "blockdev-snapshot-sync" and "mirror". (json-string)
- "data": a dictionary. The contents depend on the value
of "type". When "type" is "blockdev-snapshot-sync":
- "device": device name to snapshot (json-string)
@@ -724,6 +728,12 @@ actions array:
- "format": format of new image (json-string, optional)
- "mode": whether and how QEMU should create the snapshot file
(NewImageMode, optional, default "absolute-paths")
+ When "type" is "drive-mirror":
+ - "device": device name to snapshot (json-string)
+ - "target": name of destination image file (json-string)
+ - "format": format of new image (json-string, optional)
+ - "mode": how QEMU should look for an existing image file
+ (NewImageMode, optional, default "absolute-paths")
Example:
--
1.7.7.6
- Re: [Qemu-devel] [PATCH v3 2/8] qapi: complete implementation of unions, (continued)
- [Qemu-devel] [PATCH v3 1/8] fix format name for backing file, Paolo Bonzini, 2012/03/05
- [Qemu-devel] [PATCH v3 6/8] Add blkmirror block driver, Paolo Bonzini, 2012/03/05
- [Qemu-devel] [PATCH v3 7/8] add mirroring to transaction,
Paolo Bonzini <=
- [Qemu-devel] [PATCH v3 4/8] add mode field to blockdev-snapshot-sync transaction item, Paolo Bonzini, 2012/03/05
- [Qemu-devel] [PATCH v3 8/8] add drive-mirror command and HMP equivalent, Paolo Bonzini, 2012/03/05
- [Qemu-devel] [PATCH v3 9/8] Add the drive-reopen command, Paolo Bonzini, 2012/03/06
- [Qemu-devel] [PATCH v3 10/8] use QSIMPLEQ_FOREACH_SAFE when freeing list elements, Paolo Bonzini, 2012/03/06