On 16.04.2014 16:40, Kevin Wolf wrote:
Am 12.04.2014 um 20:57 hat Max Reitz geschrieben:
qemu-img should use QMP commands whenever possible in order to ensure
feature completeness of both online and offline image operations. As
qemu-img itself has no access to QMP (since this would basically require
just everything being linked into qemu-img), imitate QMP's
implementation of block-commit by using commit_active_start() and then
waiting for the block job to finish.
This new implementation does not empty the snapshot image, as opposed to
the old implementation using bdrv_commit(). However, as QMP's
block-commit apparently never did this and as qcow2 (which is probably
qemu's standard image format) does not even implement the required
function (bdrv_make_empty()), it does not seem necessary.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
block/Makefile.objs | 2 +-
qemu-img.c | 86 +++++++++++++++++++++++++++++++++++++++++------------
2 files changed, 68 insertions(+), 20 deletions(-)
diff --git a/block/Makefile.objs b/block/Makefile.objs
index fd88c03..2c37e80 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -9,6 +9,7 @@ block-obj-y += snapshot.o qapi.o
block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
block-obj-$(CONFIG_POSIX) += raw-posix.o
block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+block-obj-y += mirror.o
ifeq ($(CONFIG_POSIX),y)
block-obj-y += nbd.o nbd-client.o sheepdog.o
@@ -22,7 +23,6 @@ endif
common-obj-y += stream.o
common-obj-y += commit.o
-common-obj-y += mirror.o
common-obj-y += backup.o
iscsi.o-cflags := $(LIBISCSI_CFLAGS)
diff --git a/qemu-img.c b/qemu-img.c
index 8455994..9fe6384 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -30,6 +30,7 @@
#include "qemu/osdep.h"
#include "sysemu/sysemu.h"
#include "block/block_int.h"
+#include "block/blockjob.h"
#include "block/qapi.h"
#include <getopt.h>
@@ -682,12 +683,49 @@ fail:
return ret;
}
+struct CommonBlockJobCBInfo {
+ Error **errp;
+ bool done;
Looks unused (set, but never read).
Right, it's an artifact from an earlier version and in-between work.
+};
+
+static void common_block_job_cb(void *opaque, int ret)
+{
+ struct CommonBlockJobCBInfo *cbi = opaque;
+
+ if (ret < 0) {
+ error_setg_errno(cbi->errp, -ret, "Block job failed");
+ }
In practice, I guess this will give us rather bad error messages.
Perhaps we need to replace 'int ret' with 'Error *errp' for block job
callbacks in a followup.
Probably, yes.
+
+ cbi->done = true;
+}
+
+static void run_block_job(BlockJob *job, struct CommonBlockJobCBInfo *cbi)
+{
+ BlockJobInfo *info;
+
+ do {
+ qemu_aio_wait();
+
+ info = block_job_query(job);
Where does info get freed?
That, indeed, is a good question. I'll fix it, thanks.
+
+ if (!info->busy && info->offset < info->len) {
+ block_job_resume(job);
+ }
+ } while (info->offset < info->len);
+
+ block_job_complete_sync(job, cbi->errp);
+}
+
+/* Same as in block.c */
+#define COMMIT_BUF_SECTORS 2048
[...]
+ commit_active_start(bs, base_bs, 0, COMMIT_BUF_SECTORS << BDRV_SECTOR_BITS,
+ BLOCKDEV_ON_ERROR_REPORT, common_block_job_cb, &cbi,
+ &local_err);
Though bdrv_commit() uses it for a different purpose: There it's the
buffer size that is used for committing. A single request can never be
larger than this value, but depending on bdrv_is_allocated() it can be
smaller. So the granularity for the decision whether to copy data is
still the granularity of bdrv_is_allocated(), i.e. one cluster.
For the mirror block job, the decision is taken on the granularity that
you specify. This should be the same as for bdrv_commit(), i.e. the
default that you get when you specify 0. mirror_start_job() also has a
buf_size parameter, which is however not exposed by
commit_active_start(). This is where COMMIT_BUF_SECTORS would be right.
Hm, interesting. I remembered trying this and it being pretty slow (test
20 and some other test images). However, I can't reproduce it any
longer. I guess that means I can drop patch 1 of this series, too.
Max
