[dm-devel] [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm
Tejun Heo
tj at kernel.org
Wed Sep 1 11:20:08 UTC 2010
Hello,
On 09/01/2010 12:31 PM, Mikulas Patocka wrote:
> My recommended approach to this (on non-request-based dm) is to simply let
> the current barrier infrastructure be as it is --- you don't need to
> change it now, you can simply map FUA write to barrier write and FLUSH to
> zero-data barrier --- and it won't cause any data corruption. It will just
> force unneeded I/O queue draining.
>
> Once FLUSH+FUA interface is finalized and committed upstream, we can
> remove that I/O queue draining from dm to improve performance.
Unfortunately, it doesn't work that way. The current dm
implementation depends on block layer holding the queue while a
barrier sequence is in progress which the new implementation doesn't
do anymore (the whole point of this conversion BTW).
Thanks.
--
tejun
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