On 2013年12月14日 02:26, Kevin Wolf wrote:
Am 26.11.2013 um 06:45 hat Fam Zheng geschrieben:
If active is top, it will be mirrored to base, (with block/mirror.c
code), then the image is switched when user completes the block job.
QMP documentation is updated.
Signed-off-by: Fam Zheng <f...@redhat.com>
---
block/mirror.c | 11 +++++++++++
blockdev.c | 9 +++++++--
qapi-schema.json | 5 +++--
3 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index 9be741a..86ffac8 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -478,6 +478,13 @@ immediate_exit:
bdrv_reopen(s->target, bdrv_get_flags(s->common.bs), NULL);
}
bdrv_swap(s->target, s->common.bs);
+ if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) {
+ /* drop the bs loop chain formed by the swap: break the loop then
+ * trigger the unref from the top one */
+ BlockDriverState *p = s->base->backing_hd;
+ s->base->backing_hd = NULL;
+ bdrv_unref(p);
Dropping "p" here (points to sn1 in your example) recursively results in ...
I'm not sure about the refcounts...
Let's assume we have the following backing file chain, refcount in
brackets:
+------ NBD server
v
base (1) <-- sn1 (1) <-- sn2 (3) <-- guest
^
+------ something else ;-)
+ }
}
bdrv_unref(s->target);
block_job_completed(&s->common, ret);
@@ -619,6 +626,10 @@ void commit_active_start(BlockDriverState *bs,
BlockDriverState *base,
BlockDriverCompletionFunc *cb,
void *opaque, Error **errp)
{
+ if (bdrv_reopen(base, bs->open_flags, errp)) {
+ return;
+ }
+ bdrv_ref(base);
So when we start, the refcount changes as follows:
+--- commit job +------ NBD server
v v
base (2) <-- sn1 (1) <-- sn2 (3) <-- guest
^
+------ something else
Once all the data is copied over, we get o the code above, and first do
a bdrv_swap, which results in the following:
+--- commit job +------ NBD server
v v
sn2 (2) <-- sn1 (1) base (3) <-- guest
| ^ ^
+------------+ +------ something else
Break the loop (but no refcount update!):
+--- commit job +------ NBD server
v v
sn2 (2) <-- sn1 (1) base (3) <-- guest
^
+------ something else
... sn2(1) left alone. It is also reference by s->target and is
bdrv_unref'ed right before block_job_completed(). So...
Drop the commit job's reference:
+------ NBD server
v
sn2 (1) <-- sn1 (1) base (3) <-- guest
^
+------ something else
you mean sn2 (1) <-- sn1 (1) is leaked but I double checked it is not.
(Did you overlooked the bdrv_unref(p)?)
Fam
