From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44655) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZlddN-0007qu-GQ for qemu-devel@nongnu.org; Mon, 12 Oct 2015 09:59:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZlddH-0000jl-Sw for qemu-devel@nongnu.org; Mon, 12 Oct 2015 09:59:25 -0400 Date: Mon, 12 Oct 2015 15:59:10 +0200 From: Kevin Wolf Message-ID: <20151012135910.GF4153@noname.str.redhat.com> References: <1444650651-26227-1-git-send-email-famz@redhat.com> <1444650651-26227-6-git-send-email-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1444650651-26227-6-git-send-email-famz@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 05/12] block: Introduce "drained begin/end" API List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: Paolo Bonzini , qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi Am 12.10.2015 um 13:50 hat Fam Zheng geschrieben: > The semantics is that after bdrv_drained_begin(bs), bs will not get new external > requests until the matching bdrv_drained_end(bs). > > Signed-off-by: Fam Zheng > --- > block.c | 2 ++ > block/io.c | 18 ++++++++++++++++++ > include/block/block.h | 19 +++++++++++++++++++ > include/block/block_int.h | 2 ++ > 4 files changed, 41 insertions(+) > > diff --git a/block.c b/block.c > index 1f90b47..9b28a07 100644 > --- a/block.c > +++ b/block.c > @@ -2058,6 +2058,8 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest, > bs_dest->device_list = bs_src->device_list; > bs_dest->blk = bs_src->blk; > > + bs_dest->quiesce_counter = bs_src->quiesce_counter; > + > memcpy(bs_dest->op_blockers, bs_src->op_blockers, > sizeof(bs_dest->op_blockers)); > } This feels wrong. As I understand it, bdrv_drained_begin/end works on specific nodes and not on trees. Including the field in bdrv_move_feature_fields() means that it moves to the top of the tree (i.e. it stays at in the same C object, which however belongs to a different logical node now). What I could imagine is that you did this so you can use bdrv_draind_end() on the same BDS as you called bdrv_drained_start() on. However, that's not the interface of bdrv_swap(), which really means that the BDSes are swapped. So with this hunk you just end up having a bug that cancels out the weirdness of the bdrv_swap() interface. If you rebase on my bdrv_swap() removal series, things become a bit more obvious. If you don't, you should drop this hunk and change some bdrv_drained_end() calls, e.g. in the next patch, you'd have to call bdrv_drained_begin(state->old_bs), but bdrv_drained_end(state->new_bs). The rest of this patch looks good. Kevin