From: Tejun Heo <tj@kernel.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: jaxboe@fusionio.com, k-ueda@ct.jp.nec.com,
j-nomura@ce.jp.nec.com, jamie@shareable.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-raid@vger.kernel.org, hch@lst.de, dm-devel@redhat.com
Subject: Re: [PATCH 2/5] dm: implement REQ_FLUSH/FUA support for bio-based dm
Date: Wed, 01 Sep 2010 15:50:48 +0200 [thread overview]
Message-ID: <4C7E5A38.9050001@kernel.org> (raw)
In-Reply-To: <20100901134343.GA25260@redhat.com>
Hello,
On 09/01/2010 03:43 PM, Mike Snitzer wrote:
> On Mon, Aug 30 2010 at 5:58am -0400,
> Tejun Heo <tj@kernel.org> 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 doesn't happen anymore. If the underlying device doesn't
support FLUSH/FUA, the block layer simply make those parts noop. IOW,
it no longer distinguishes between writeback cache which doesn't
support cache flush at all and writethrough cache. Devices which have
WB cache w/o flush very difficult to come by these days and there's
nothing much we can do anyway, so it doesn't 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.
Thanks.
--
tejun
next prev parent reply other threads:[~2010-09-01 13:50 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1283162296-13650-1-git-send-email-tj@kernel.org>
2010-08-30 9:58 ` [PATCH 1/5] block: make __blk_rq_prep_clone() copy most command flags Tejun Heo
2010-08-30 9:58 ` [PATCH 2/5] dm: implement REQ_FLUSH/FUA support for bio-based dm Tejun Heo
2010-09-01 13:43 ` Mike Snitzer
2010-09-01 13:50 ` Tejun Heo [this message]
2010-09-01 13:54 ` Mike Snitzer
2010-09-01 13:56 ` Tejun Heo
2010-08-30 9:58 ` [PATCH 3/5] dm: relax ordering of bio-based flush implementation Tejun Heo
2010-08-30 9:58 ` [PATCH 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Tejun Heo
2010-08-30 9:58 ` [PATCH 5/5] block: remove the WRITE_BARRIER flag Tejun Heo
[not found] ` <1283162296-13650-5-git-send-email-tj@kernel.org>
2010-08-30 13:28 ` [PATCH 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Mike Snitzer
[not found] ` <20100830132836.GB5283@redhat.com>
2010-08-30 13:59 ` Tejun Heo
[not found] ` <4C7BB932.1070405@kernel.org>
2010-08-30 15:07 ` Tejun Heo
2010-08-30 15:42 ` [PATCH] block: initialize flush request with WRITE_FLUSH instead of REQ_FLUSH Tejun Heo
2010-08-30 15:45 ` [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Tejun Heo
[not found] ` <4C7BC942.7070703@kernel.org>
2010-08-30 19:08 ` [PATCH " Mike Snitzer
[not found] ` <20100830190835.GA8458@redhat.com>
2010-08-30 21:28 ` Mike Snitzer
2010-08-31 10:29 ` Tejun Heo
2010-08-31 13:02 ` Mike Snitzer
2010-08-31 13:14 ` Tejun Heo
[not found] ` <4C7BD202.4040700@kernel.org>
2010-08-30 19:18 ` [PATCH UPDATED " Mike Snitzer
[not found] ` <20100830194731.GA10702@redhat.com>
2010-09-01 10:31 ` Mikulas Patocka
2010-09-01 11:20 ` Tejun Heo
2010-09-01 12:12 ` Mikulas Patocka
2010-09-01 12:42 ` Tejun Heo
2010-09-01 12:54 ` Mike Snitzer
2010-09-01 15:20 ` Mike Snitzer
2010-09-01 15:35 ` Mikulas Patocka
2010-09-01 17:07 ` Mike Snitzer
2010-09-01 18:59 ` Mike Snitzer
2010-09-02 3:22 ` Mike Snitzer
2010-09-02 10:24 ` Tejun Heo
2010-09-02 15:11 ` Mike Snitzer
2010-09-09 15:26 ` [REGRESSION][BISECTED] virtio-blk serial attribute causes guest to hang [Was: Re: [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm] Mike Snitzer
2010-09-09 15:44 ` Ryan Harper
2010-09-09 15:57 ` Mike Snitzer
2010-09-09 16:03 ` Ryan Harper
2010-09-09 17:55 ` Mike Snitzer
2010-09-09 18:35 ` Ryan Harper
2010-09-09 19:15 ` Mike Snitzer
2010-09-09 19:43 ` Mike Snitzer
2010-09-09 20:14 ` Mike Snitzer
2010-09-09 20:30 ` Ryan Harper
2010-09-09 21:00 ` [PATCH] virtio-blk: put request that was created to retrieve the device id Mike Snitzer
2010-09-09 21:15 ` Christoph Hellwig
2010-09-17 14:58 ` Ryan Harper
2010-09-21 21:00 ` Christoph Hellwig
2010-10-08 16:06 ` [2.6.36 REGRESSION] " Mike Snitzer
2010-10-09 1:41 ` [PATCH] " Rusty Russell
[not found] ` <1283162296-13650-4-git-send-email-tj@kernel.org>
2010-09-01 13:51 ` [PATCH 3/5] dm: relax ordering of bio-based flush implementation Mike Snitzer
2010-09-01 13:56 ` Tejun Heo
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