On Fri, May 23, 2014 at 11:23:23AM +0800, Fam Zheng wrote: > This makes use of op_blocker and blocks all the operations except for > commit target, on each BlockDriverState->backing_hd. > > The asserts for op_blocker in bdrv_swap are removed because with this > change, the target of block commit has at least the backing blocker of > its child, so the assertion is not true. Callers should do their check. > > Signed-off-by: Fam Zheng <f...@redhat.com> > --- > block.c | 22 ++++++++++++++++++---- > block/mirror.c | 2 +- > include/block/block_int.h | 3 +++ > 3 files changed, 22 insertions(+), 5 deletions(-) > > diff --git a/block.c b/block.c > index 91c866c..b5aeca2 100644 > --- a/block.c > +++ b/block.c > @@ -1097,14 +1097,29 @@ fail: > void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd) > { > > + if (bs->backing_hd) { > + assert(bs->backing_blocker); > + bdrv_op_unblock_all(bs->backing_hd, bs->backing_blocker); > + } else if (backing_hd) { > + error_setg(&bs->backing_blocker, > + "device is used as backing hd of '%s'", > + bs->device_name); > + } > + > bs->backing_hd = backing_hd; > if (!backing_hd) { > + error_free(bs->backing_blocker);
bs->backing_block = NULL; ...to make the assert(bs->backing_blocker) above more useful.