From: Mike Snitzer <snitzer@redhat.com>
To: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Cc: Tejun Heo <tj@kernel.org>,
jaxboe@fusionio.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
Subject: Re: [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm
Date: Wed, 1 Sep 2010 08:25:27 -0400 [thread overview]
Message-ID: <20100901122526.GA24922@redhat.com> (raw)
In-Reply-To: <4C7DFD8F.6070200@ct.jp.nec.com>
On Wed, Sep 01 2010 at 3:15am -0400,
Kiyoshi Ueda <k-ueda@ct.jp.nec.com> wrote:
> Hi Tejun,
>
> On 08/31/2010 12:45 AM +0900, Tejun Heo wrote:
> > This patch converts request-based dm to support the new REQ_FLUSH/FUA.
> >
> > The original request-based flush implementation depended on
> > request_queue blocking other requests while a barrier sequence is in
> > progress, which is no longer true for the new REQ_FLUSH/FUA.
> >
> > In general, request-based dm doesn't have infrastructure for cloning
> > one source request to multiple targets, but the original flush
> > implementation had a special mostly independent path which can issue
> > flushes to multiple targets and sequence them. However, the
> > capability isn't currently in use and adds a lot of complexity.
> > Moreoever, it's unlikely to be useful in its current form as it
> > doesn't make sense to be able to send out flushes to multiple targets
> > when write requests can't be.
> >
> > This patch rips out special flush code path and deals handles
> > REQ_FLUSH/FUA requests the same way as other requests. The only
> > special treatment is that REQ_FLUSH requests use the block address 0
> > when finding target, which is enough for now.
> >
> > * added BUG_ON(!dm_target_is_valid(ti)) in dm_request_fn() as
> > suggested by Mike Snitzer
>
> Thank you for your work.
>
> I don't see any obvious problem on this patch.
> However, I hit a NULL pointer dereference below when I use a mpath
> device with barrier option of ext3. I'm investigating the cause now.
> (Also I'm not sure the cause of the hang which Mike is hitting yet.)
>
> I tried on the commit 28dd53b26d362c16234249bad61db8cbd9222d0b of
> git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git flush-fua.
>
> # mke2fs -j /dev/mapper/mpatha
> # mount -o barrier=1 /dev/mapper/mpatha /mnt/0
> # dd if=/dev/zero of=/mnt/0/a bs=512 count=1
> # sync
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000078
FYI, I can't reproduce this using all of Tejun's latest patches (not yet
in the flush-fua git tree). But I haven't tried the specific flush-fua
commit that you referenced.
Mike
next prev parent reply other threads:[~2010-09-01 12:25 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-30 9:58 [PATCHSET 2.6.36-rc2] block, dm: finish REQ_FLUSH/FUA conversion, take#2 Tejun Heo
2010-08-30 9:58 ` Tejun Heo
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 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-09-01 15:30 ` Christoph Hellwig
2010-08-30 9:58 ` Tejun Heo
2010-08-30 9:58 ` [PATCH 2/5] dm: implement REQ_FLUSH/FUA support for bio-based dm Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-09-01 13:43 ` Mike Snitzer
2010-09-01 13:50 ` Tejun Heo
2010-09-01 13:54 ` Mike Snitzer
2010-09-01 13:56 ` Tejun Heo
2010-08-30 9:58 ` 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 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-09-01 13:51 ` Mike Snitzer
2010-09-01 13:51 ` Mike Snitzer
2010-09-01 13:56 ` Tejun Heo
2010-09-01 13:56 ` Tejun Heo
2010-09-03 6:04 ` Kiyoshi Ueda
2010-09-03 9:42 ` 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 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-08-30 13:28 ` Mike Snitzer
2010-08-30 13:59 ` Tejun Heo
2010-08-30 15:07 ` Tejun Heo
2010-08-30 19:08 ` Mike Snitzer
2010-08-30 19:08 ` Mike Snitzer
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
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 15:42 ` Tejun Heo
2010-08-30 15:45 ` [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Tejun Heo
2010-08-30 19:18 ` Mike Snitzer
2010-08-30 19:18 ` Mike Snitzer
2010-09-01 7:15 ` Kiyoshi Ueda
2010-09-01 12:25 ` Mike Snitzer [this message]
2010-09-02 13:22 ` Tejun Heo
2010-09-02 13:32 ` Tejun Heo
2010-09-03 5:46 ` Kiyoshi Ueda
2010-09-02 17:43 ` [PATCH] block: make sure FSEQ_DATA request has the same rq_disk as the original Tejun Heo
2010-09-03 5:47 ` Kiyoshi Ueda
2010-09-03 9:33 ` Tejun Heo
2010-09-03 10:28 ` Kiyoshi Ueda
2010-09-03 11:42 ` Tejun Heo
2010-09-03 11:51 ` Kiyoshi Ueda
[not found] ` <20100830194731.GA10702@redhat.com>
2010-09-01 10:31 ` [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm 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
2010-08-30 15:45 ` [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Tejun Heo
2010-08-30 13:59 ` [PATCH " Tejun Heo
2010-08-30 13:28 ` Mike Snitzer
2010-08-30 9:58 ` [PATCH 5/5] block: remove the WRITE_BARRIER flag Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
2010-08-30 9:58 ` Tejun Heo
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