[dm-devel] Re: possible regression by the barrier patch in 2.6.30-rc2

[Kiyoshi Ueda]

Hi Alasdair, Mikulas,

On 2009/04/17 22:22 +0900, Alasdair G Kergon wrote:
> On Fri, Apr 17, 2009 at 01:57:02PM +0900, Kiyoshi Ueda wrote:
>> 1. The semantics of flush suspend has been changed.
> 
> We absolutely must complete any I/O issued as a result of the lock_fs()
> call in dm_suspend().

I think that lock_fs() waits for I/O to complete, so no semantics change
in case of LOCKFS && FLUSH. (All I/O issued from lock_fs() are flushed.)

But in case of NO_LOCKFS && FLUSH, the semantics is changed:
  from: I/Os submitted before the suspend invocation are flushed
  to:   I/Os submitted even before the suspend invocation may not be flushed

I have no idea whether someone gets real damage by this semantics change.

> Alasdair

Thanks,
Kiyoshi Ueda