| title: | Re PATCH 2 5 dm implement REQ FLUSH FUA s |
|
On Wed, Sep 01 2010 at 9:50am -0400,
Tejun Heo <tj@xxxxxxxxxx wrote:
Hello,
On 09/01/2010 03:43 PM, Mike Snitzer wrote:
On Mon, Aug 30 2010 at 5:58am -0400,
Tejun Heo <tj@xxxxxxxxxx wrote:
This patch converts bio-based dm to support REQ_FLUSH/FUA instead of
now deprecated REQ_HARDBARRIER.
* -EOPNOTSUPP handling logic dropped.
Can you expand on _why_ -EOPNOTSUPP handling is no longer needed? And
please at it to the final patch header.
It just doesnt happen anymore. If the underlying device doesnt
support FLUSH/FUA, the block layer simply make those parts noop. IOW,
it no longer distinguishes between writeback cache which doesnt
support cache flush at all and writethrough cache. Devices which have
WB cache w/o flush very difficult to come by these days and theres
nothing much we can do anyway, so it doesnt make sense to require
everyone to implement -EOPNOTSUPP.
One scheduled feature is to implement falling back to REQ_FLUSH when
the device advertises REQ_FUA but fails to process it, but one way or
the other, the goal is encapsulating REQ_FLUSH/FUA support in block
layer proper. If FLUSH/FUA can be retried using a different strategy,
it should be done inside request_queue proper instead of pushing retry
logic to all its users.
OK, so maybe add this info to the patch header one of the primary
FLUSH+FUA conversion patches?
Thanks for the detailed explanation!
Mike
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at rel="nofollow" vger.kernel.org/majordomo-info.html vger.kernel.org/majordomo-info.html
|
