From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57117) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YY6VC-0003yn-4N for qemu-devel@nongnu.org; Wed, 18 Mar 2015 01:26:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YY6V7-0000LY-R3 for qemu-devel@nongnu.org; Wed, 18 Mar 2015 01:26:46 -0400 Received: from [59.151.112.132] (port=1687 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YY6V6-0000It-Iz for qemu-devel@nongnu.org; Wed, 18 Mar 2015 01:26:41 -0400 Message-ID: <55090D42.6000502@cn.fujitsu.com> Date: Wed, 18 Mar 2015 13:29:38 +0800 From: Wen Congyang MIME-Version: 1.0 References: <1423710438-14377-1-git-send-email-wency@cn.fujitsu.com> <1423710438-14377-4-git-send-email-wency@cn.fujitsu.com> <54EB910F.5060000@redhat.com> In-Reply-To: <54EB910F.5060000@redhat.com> Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 03/14] quorum: ignore 0-length child List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz , qemu devel , Kevin Wolf , Stefan Hajnoczi , Paolo Bonzini Cc: Lai Jiangshan , Jiang Yunhong , Dong Eddie , "Dr. David Alan Gilbert" , Gonglei , Yang Hongyang , zhanghailiang On 02/24/2015 04:43 AM, Max Reitz wrote: > On 2015-02-11 at 22:07, Wen Congyang wrote: >> We connect to NBD server when starting block replication, so >> the length is 0 before starting block replication. >> >> Signed-off-by: Wen Congyang >> Signed-off-by: zhanghailiang >> Signed-off-by: Gonglei >> --- >> block/quorum.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/block/quorum.c b/block/quorum.c >> index 5ed1ff8..e6aff5f 100644 >> --- a/block/quorum.c >> +++ b/block/quorum.c >> @@ -734,6 +734,11 @@ static int64_t quorum_getlength(BlockDriverState *bs) >> if (value < 0) { >> return value; >> } >> + >> + if (!value) { >> + continue; >> + } >> + >> if (value != result) { >> return -EIO; >> } > > Hm, what do you think about some specific error value returned by your delayed NBD implementation? Like -ENOTCONN or something like that? Then we'd be able to discern a real 0-length block device from a not-yet-connected NBD server. In my newest test, it cannot return -ENOTCONN, otherwise bdrv_open() will fail when we open the child. Here is the backtrace: (gdb) bt #0 bdrv_open_common (bs=0x5555563b2230, file=0x0, options=0x5555563b55a0, flags=57410, drv=0x555555e90c00, errp=0x7fffffffd460) at block.c:1070 #1 0x000055555595ea72 in bdrv_open (pbs=0x7fffffffd5f8, filename=0x0, reference=0x0, options=0x5555563b55a0, flags=57410, drv=0x555555e90c00, errp=0x7fffffffd5e0) at block.c:1677 #2 0x000055555595e3a9 in bdrv_open_image (pbs=0x7fffffffd5f8, filename=0x0, options=0x5555563a6730, bdref_key=0x555555a86b4c "file", flags=57410, allow_none=true, errp=0x7fffffffd5e0) at block.c:1481 #3 0x000055555595e9ae in bdrv_open (pbs=0x555556388008, filename=0x0, reference=0x0, options=0x5555563a6730, flags=8258, drv=0x555555e8b800, errp=0x7fffffffd6b8) at block.c:1655 #4 0x00005555559b0058 in quorum_open (bs=0x55555639bd90, options=0x55555639f100, flags=8258, errp=0x7fffffffd758) at block/quorum.c:1000 #5 0x000055555595d0b8 in bdrv_open_common (bs=0x55555639bd90, file=0x0, options=0x55555639f100, flags=8258, drv=0x555555e8e5c0, errp=0x7fffffffd840) at block.c:1045 #6 0x000055555595ea72 in bdrv_open (pbs=0x55555639bd50, filename=0x0, reference=0x0, options=0x55555639f100, flags=8258, drv=0x555555e8e5c0, errp=0x7fffffffdb70) at block.c:1677 #7 0x00005555559b3bd3 in blk_new_open (name=0x55555639bc60 "virtio0", filename=0x0, reference=0x0, options=0x55555639a420, flags=66, errp=0x7fffffffdb70) at block/block-backend.c:129 #8 0x0000555555754f78 in blockdev_init (file=0x0, bs_opts=0x55555639a420, errp=0x7fffffffdb70) at blockdev.c:536 #9 0x0000555555755d90 in drive_new (all_opts=0x5555563777e0, block_default_type=IF_IDE) at blockdev.c:971 #10 0x000055555576b1f0 in drive_init_func (opts=0x5555563777e0, opaque=0x555556372b48) at vl.c:1104 #11 0x0000555555a1b019 in qemu_opts_foreach (list=0x555555e44060, func=0x55555576b1ba , opaque=0x555556372b48, abort_on_failure=1) at util/qemu-option.c:1059 #12 0x00005555557743dd in main (argc=25, argv=0x7fffffffe0c8, envp=0x7fffffffe198) at vl.c:4191 refresh_total_sectors() will fail if we return -ENOTCONN. Thanks Wen Congyang > > Also, while you did write that one shouldn't be using the NBD client as the first quorum child, I think we should try to support that case anyway. For this patch, that means accepting that bdrv_getlength(s->bs[0]) may be off. > > Max > . >