From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56240) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y9KVC-0007qf-M8 for qemu-devel@nongnu.org; Thu, 08 Jan 2015 16:20:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y9KV8-0002Sq-Ke for qemu-devel@nongnu.org; Thu, 08 Jan 2015 16:20:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47384) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y9KV8-0002Sk-BL for qemu-devel@nongnu.org; Thu, 08 Jan 2015 16:20:18 -0500 Message-ID: <54AEF48F.6010405@redhat.com> Date: Thu, 08 Jan 2015 16:20:15 -0500 From: John Snow MIME-Version: 1.0 References: <1418307457-25996-1-git-send-email-vsementsov@parallels.com> <1418307457-25996-3-git-send-email-vsementsov@parallels.com> In-Reply-To: <1418307457-25996-3-git-send-email-vsementsov@parallels.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/9] block-migration: fix pending() return value List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org Cc: kwolf@redhat.com, "juan quin >> Juan Jose Quintela Carreira" , "dg >> Dr. David Alan Gilbert" , stefanha@redhat.com, amit Shah , den@openvz.org On 12/11/2014 09:17 AM, Vladimir Sementsov-Ogievskiy wrote: > Because of wrong return value of .save_live_pending() in > block-migration, migration finishes before the whole disk > is transferred. Such situation occures when the migration (occurs) > process is fast enouth, for example when source and dest (enough) > are on the same host. > > If in the bulk phase we return something < max_size, we will skip > transferring the tail of the device. Currently we have "set pending to > BLOCK_SIZE if it is zero" for bulk phase, but there no guarantee, that > it will be < max_size. > > True approach is to return, for example, max_size+1 when we are in the > bulk phase. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block-migration.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block-migration.c b/block-migration.c > index 6f3aa18..8df30d9 100644 > --- a/block-migration.c > +++ b/block-migration.c > @@ -757,8 +757,8 @@ static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size) > block_mig_state.read_done * BLOCK_SIZE; > > /* Report at least one block pending during bulk phase */ > - if (pending == 0 && !block_mig_state.bulk_completed) { > - pending = BLOCK_SIZE; > + if (pending <= max_size && !block_mig_state.bulk_completed) { > + pending = max_size + BLOCK_SIZE; > } > blk_mig_unlock(); > qemu_mutex_unlock_iothread(); > This looks sane to me, but I am CC'ing the Migration maintainers to give it a proper look. Looks to me like this is to prevent this from happening, in migration/migration.c: pending_size = qemu_savevm_state_pending(s->file, max_size); trace_migrate_pending(pending_size, max_size); if (pending_size && pending_size >= max_size) { If we fail that condition, we omit data because we do not call qemu_savevm_state_iterate.