From: Phillip Susi <psusi@cfl.rr.com>
To: Stefan Bader <Stefan.Bader@de.ibm.com>
Cc: Tejun Heo <htejun@gmail.com>,
Stefan Bader <sbader3@googlemail.com>,
David Chinner <dgc@sgi.com>,
linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
device-mapper development <dm-devel@redhat.com>,
Jens Axboe <jens.axboe@oracle.com>,
linux-fsdevel@vger.kernel.org,
Andreas Dilger <adilger@clusterfs.com>
Subject: Re: Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md.
Date: Wed, 30 May 2007 12:55:14 -0400 [thread overview]
Message-ID: <465DAC72.1010201@cfl.rr.com> (raw)
In-Reply-To: <5201e28f0705300212g3be16464u5ee1a4c80db27a11@mail.gmail.com>
Stefan Bader wrote:
> You got a linear target that consists of two disks. One drive (a)
> supports barriers and the other one (b) doesn't. Device-mapper just
> maps the requests to the appropriate disk. Now the following sequence
> happens:
>
> 1. block x gets mapped to drive b
> 2. block y (with barrier) gets mapped to drive a
>
> Since drive a supports barrier request we don't get -EOPNOTSUPP but
> the request with block y might get written before block x since the
> disk are independent. I guess the chances of this are quite low since
> at some point a barrier request will also hit drive b but for the time
> being it might be better to indicate -EOPNOTSUPP right from
> device-mapper.
The device mapper needs to ensure that ALL underlying devices get a
barrier request when one comes down from above, even if it has to
construct zero length barriers to send to most of them.
WARNING: multiple messages have this Message-ID (diff)
From: Phillip Susi <psusi@cfl.rr.com>
To: Stefan Bader <Stefan.Bader@de.ibm.com>
Cc: Stefan Bader <sbader3@googlemail.com>,
device-mapper development <dm-devel@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-raid@vger.kernel.org, Jens Axboe <jens.axboe@oracle.com>,
David Chinner <dgc@sgi.com>,
Andreas Dilger <adilger@clusterfs.com>,
Tejun Heo <htejun@gmail.com>
Subject: Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md.
Date: Wed, 30 May 2007 12:55:14 -0400 [thread overview]
Message-ID: <465DAC72.1010201@cfl.rr.com> (raw)
In-Reply-To: <5201e28f0705300212g3be16464u5ee1a4c80db27a11@mail.gmail.com>
Stefan Bader wrote:
> You got a linear target that consists of two disks. One drive (a)
> supports barriers and the other one (b) doesn't. Device-mapper just
> maps the requests to the appropriate disk. Now the following sequence
> happens:
>
> 1. block x gets mapped to drive b
> 2. block y (with barrier) gets mapped to drive a
>
> Since drive a supports barrier request we don't get -EOPNOTSUPP but
> the request with block y might get written before block x since the
> disk are independent. I guess the chances of this are quite low since
> at some point a barrier request will also hit drive b but for the time
> being it might be better to indicate -EOPNOTSUPP right from
> device-mapper.
The device mapper needs to ensure that ALL underlying devices get a
barrier request when one comes down from above, even if it has to
construct zero length barriers to send to most of them.
next prev parent reply other threads:[~2007-05-30 16:55 UTC|newest]
Thread overview: 134+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-25 7:58 [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md Neil Brown
2007-05-25 7:58 ` Neil Brown
2007-05-25 11:15 ` David Chinner
2007-05-25 11:49 ` Jens Axboe
2007-05-25 14:49 ` Phillip Susi
2007-05-25 14:49 ` [dm-devel] " Phillip Susi
2007-05-28 18:32 ` Jens Axboe
2007-05-25 13:52 ` Stefan Bader
2007-05-28 1:37 ` Neil Brown
2007-05-29 9:12 ` Stefan Bader
2007-05-25 15:11 ` Phillip Susi
2007-05-25 15:11 ` [dm-devel] " Phillip Susi
2007-05-26 1:03 ` Andreas Dilger
2007-05-26 10:27 ` Tejun Heo
2007-05-28 1:30 ` Neil Brown
2007-05-28 2:45 ` David Chinner
2007-05-28 2:57 ` Neil Brown
2007-05-28 4:29 ` David Chinner
2007-05-28 4:29 ` David Chinner
2007-05-31 0:46 ` Neil Brown
2007-05-31 0:57 ` Alasdair G Kergon
2007-05-31 0:57 ` [dm-devel] " Alasdair G Kergon
2007-05-31 1:07 ` Alasdair G Kergon
2007-05-31 1:07 ` [dm-devel] " Alasdair G Kergon
2007-05-31 1:11 ` David Chinner
2007-05-31 1:11 ` [dm-devel] " David Chinner
2007-05-28 4:48 ` Timothy Shimmin
2007-05-29 6:45 ` Jeremy Higdon
2007-05-29 20:03 ` Phillip Susi
2007-05-29 23:48 ` David Chinner
2007-05-30 0:01 ` david
2007-05-30 6:17 ` David Chinner
2007-05-30 8:55 ` Stefan Bader
2007-05-30 8:55 ` Stefan Bader
2007-05-30 16:52 ` david
2007-05-30 16:52 ` david
2007-05-31 0:20 ` David Chinner
2007-05-31 6:26 ` Jens Axboe
2007-05-31 7:03 ` David Chinner
2007-05-31 7:06 ` Jens Axboe
2007-05-31 13:30 ` Bill Davidsen
2007-05-31 13:36 ` Jens Axboe
2007-06-01 16:04 ` Bill Davidsen
2007-06-02 14:51 ` Jens Axboe
2007-06-02 19:55 ` Bill Davidsen
2007-06-01 3:16 ` Tejun Heo
2007-06-01 3:16 ` Tejun Heo
2007-06-01 8:21 ` Jens Axboe
2007-06-01 8:21 ` Jens Axboe
2007-06-02 9:20 ` Tejun Heo
2007-06-02 14:34 ` Jens Axboe
2007-06-02 14:34 ` Jens Axboe
2007-06-02 22:57 ` Guy Watkins
2007-06-02 22:57 ` Guy Watkins
2007-06-04 7:39 ` Tejun Heo
2007-05-31 18:31 ` Phillip Susi
2007-05-31 19:00 ` Jens Axboe
2007-05-31 19:21 ` david
2007-05-31 19:21 ` david
2007-05-31 19:40 ` Jens Axboe
2007-05-31 23:34 ` David Chinner
2007-06-01 5:59 ` Neil Brown
2007-06-01 6:11 ` Jens Axboe
2007-06-01 7:53 ` David Chinner
2007-06-01 23:56 ` Bill Davidsen
2007-05-31 18:24 ` Phillip Susi
2007-05-31 18:24 ` Phillip Susi
2007-05-30 16:45 ` Phillip Susi
2007-05-30 20:27 ` [dm-devel] " Phillip Susi
2007-05-31 6:24 ` Jens Axboe
2007-05-31 6:24 ` [dm-devel] " Jens Axboe
2007-05-31 18:37 ` Phillip Susi
2007-05-31 18:58 ` Jens Axboe
2007-06-02 0:04 ` Bill Davidsen
2007-05-28 9:29 ` Tejun Heo
2007-05-28 9:43 ` Alasdair G Kergon
2007-05-28 9:43 ` [dm-devel] " Alasdair G Kergon
2007-05-29 9:25 ` Stefan Bader
2007-05-29 22:05 ` Alasdair G Kergon
2007-05-29 22:05 ` [dm-devel] " Alasdair G Kergon
2007-05-30 9:12 ` Stefan Bader
2007-05-30 10:41 ` Alasdair G Kergon
2007-05-30 10:41 ` [dm-devel] " Alasdair G Kergon
2007-05-30 16:55 ` Phillip Susi [this message]
2007-05-30 16:55 ` Phillip Susi
2007-05-31 11:14 ` Stefan Bader
2007-06-01 3:25 ` Tejun Heo
2007-06-01 3:25 ` [dm-devel] " Tejun Heo
2007-06-01 5:55 ` david
2007-06-01 5:55 ` [dm-devel] " david
2007-06-01 7:16 ` Tejun Heo
2007-06-01 17:07 ` Valdis.Kletnieks
2007-06-01 18:09 ` Tejun Heo
2007-07-10 18:39 ` Ric Wheeler
2007-07-10 23:40 ` Valdis.Kletnieks
2007-07-11 2:49 ` Tejun Heo
2007-07-11 22:44 ` Ric Wheeler
2007-07-12 17:34 ` Valdis.Kletnieks
2007-07-12 19:43 ` Ric Wheeler
2007-07-12 23:10 ` Guy Watkins
2007-07-12 23:10 ` Guy Watkins
2007-07-13 11:30 ` Ric Wheeler
2007-07-11 2:51 ` Tejun Heo
2007-05-29 19:59 ` Phillip Susi
2007-05-31 0:22 ` Neil Brown
2007-05-30 9:35 ` Jens Axboe
2007-07-05 12:28 ` Tejun Heo
2007-07-09 12:27 ` Jens Axboe
2007-07-18 10:56 ` [PATCH] block: cosmetic changes Tejun Heo
2007-07-18 10:56 ` Tejun Heo
2007-07-18 10:59 ` [PATCH] block: factor out bio_check_eod() Tejun Heo
2007-07-18 10:59 ` Tejun Heo
2007-07-18 11:06 ` Jens Axboe
2007-07-18 11:18 ` Tejun Heo
2007-07-18 11:18 ` Tejun Heo
2007-07-18 11:31 ` Jens Axboe
2007-07-18 11:31 ` Jens Axboe
2007-07-18 11:33 ` Tejun Heo
2007-07-18 11:33 ` Tejun Heo
2007-07-18 11:34 ` Jens Axboe
2007-07-18 11:34 ` Jens Axboe
2007-07-18 11:41 ` Tejun Heo
2007-07-18 11:41 ` Tejun Heo
2007-07-18 11:45 ` Jens Axboe
2007-07-18 11:49 ` Jens Axboe
2007-07-18 12:34 ` Tejun Heo
2007-07-18 12:31 ` Jens Axboe
2007-05-28 11:17 ` [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md Nikita Danilov
2007-05-31 3:31 ` Neil Brown
2007-05-28 14:43 ` Bill Davidsen
2007-05-28 14:43 ` Bill Davidsen
2007-05-31 0:37 ` Neil Brown
2007-05-31 12:28 ` Bill Davidsen
2007-05-31 12:28 ` Bill Davidsen
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