[Xen-devel] request of blkfront may disorder after migration without waiting in suspend phase of migration

[alice wan <wanjia19870902@xxxxxxxxx>]

Hi konrad,

 

I found the mainline linux 3.0-rc6 xen-blkfront driver doesn't implement suspend func. In my opinion, the blkfront should wait till responses of all the pending requests come back, then domu can be suspended, otherwise,  after the migration, vm of target host will request from target host, meanwhile, the blkback of source host maybe do the pending requests until they's done.

 

if migrate the vm with high io pressure,  the requests of this vm may disorder.

 

And i saw the gpl windows pv driver, blkfront will change its state and wait for blkback closing, after blkback closing, the pending requests definitely are done.

 

More, i did some test with migration,  while vm was running dd task,  xm migrate -l .  before it suspend, gdb tapdisk2.  after migration, new vm started. then quit gdb, the pending request were written back to disk after new requests.

 

above mentioned is just my opinion, i need your advice and confirmation or deny

 

any help is appreciated.

 

 

Regards

 

wanjia

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