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Date: Thu, 29 Mar 2018 12:25:10 +0800
From: Peter Xu <peterx@redhat.com>
Message-ID: <20180329042510.GC8456@xz-mi>
References: <20180327091043.30220-1-xiaoguangrong@tencent.com>
	<20180327091043.30220-5-xiaoguangrong@tencent.com>
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Subject: Re: [Qemu-devel] [PATCH v2 04/10] migration: detect compression and
 decompression errors
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To: Xiao Guangrong <guangrong.xiao@gmail.com>
Cc: pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, dgilbert@redhat.com, jiang.biao2@zte.com.cn, wei.w.wang@intel.com, Xiao Guangrong <xiaoguangrong@tencent.com>

On Thu, Mar 29, 2018 at 11:51:03AM +0800, Xiao Guangrong wrote:
> 
> 
> On 03/28/2018 05:59 PM, Peter Xu wrote:
> > On Tue, Mar 27, 2018 at 05:10:37PM +0800, guangrong.xiao@gmail.com wrote:
> > 
> > [...]
> > 
> > > -static int compress_threads_load_setup(void)
> > > +static int compress_threads_load_setup(QEMUFile *f)
> > >   {
> > >       int i, thread_count;
> > > @@ -2665,6 +2685,7 @@ static int compress_threads_load_setup(void)
> > >           }
> > >           decomp_param[i].stream.opaque = &decomp_param[i];
> > > +        decomp_param[i].file = f;
> > 
> > On the source side the error will be set via:
> > 
> >          qemu_file_set_error(migrate_get_current()->to_dst_file, blen);
> > 
> > Maybe we can do similar things using migrate_incoming_get_current() to
> > avoid caching the QEMUFile multiple times?
> > 
> 
> I have considered it, however, it can not work as the @file used by ram
> loader is not the file got from migrate_incoming_get_current() under some
> cases.
> 
> For example, in colo_process_incoming_thread(), the file passed to
> qemu_loadvm_state() is a internal buffer and it is not easy to switch it
> to incoming file.

I see. How about cache it in a global variable?  We have these
already:

    thread_count = migrate_decompress_threads();
    decompress_threads = g_new0(QemuThread, thread_count);
    decomp_param = g_new0(DecompressParam, thread_count);
    ...

IMHO we can add a new one too, at least we don't cache it multiple
times (after all decomp_param[i]s are global variables too).

-- 
Peter Xu