Hello,

On 08/23/2010 04:08 PM, Christoph Hellwig wrote:

On Mon, Aug 23, 2010 at 04:01:15PM +0200, Jens Axboe wrote:

quoted

The problem purely exists on arrays that report write back cache enabled
AND don't implement SYNC_CACHE as a noop. Do any of them exist, or are
they purely urban legend?

I haven't seen it.  I don't care particularly about this case, but once
it a while people want to disable flushing for testing or because they
really don't care.

What about adding a sysfs attribue to every request_queue that allows
disabling the cache flushing feature?  Compared to the barrier option
this controls the feature at the right level and makes it available
to everyone instead of beeing duplicated.  After a while we can then
simply ignore the barrier/nobarrier options.

Yeah, that sounds reasonable.  blk_queue_flush() can be called anytime
without locking anyway, so it should be really easy to implement too.

Thanks.

-- 
tejun