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Date: Thu, 3 Jun 2010 12:30:01 -0400
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Christof Schmitt <christof.schmitt@de.ibm.com>, linux-scsi@vger.kernel.org,
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       "Martin K. Petersen" <martin.petersen@oracle.com>,
       Ric Wheeler <rwheeler@redhat.com>,
       Matthew Wilcox <willy@linux.intel.com>,
       Vladislav Bolkhovitin <vst@vlnb.net>, Christoph Hellwig <hch@lst.de>
Subject: Re: [Lsf10-pc] [LFS/VM TOPIC] Stable pages while IO (was Wrong DIF
	guard tag on ext2 write)
Message-ID: <20100603163001.GF24994@fieldses.org>
References: <20100531112817.GA16260@schmichrtp.mainz.de.ibm.com> <4C07D3D0.8010500@panasas.com>
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From: "J. Bruce Fields" <bfields@fieldses.org>
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On Thu, Jun 03, 2010 at 07:09:52PM +0300, Boaz Harrosh wrote:
> [Topic]
> How to not let pages change while in IO
> 
> [Abstract]
> As seen in a long thread on the fsdvel scsi mailing lists. Lots of
> people have headaches and sleep less nights because individual pages
> can change while in IO and/or DMA. Though each one as slightly different
> needs, the mechanics look to be the same.
> 
> People that care:
> - Mirror and RAID people that need on disk consistency.
> - Network storage that wants data checksum.

Yes, nfs/rpcsec_gss code is an example of code that tries to sign pages
containing data that could change underneath us.  I don't know if we've
seen it in practice.

--b.

> - DIF/DIX people
> - ...
> 
> I for one know nothing of the subject but am a RAID person and would
> like a solution that does not force me to copy the complete data load.
> 
> Please lets get all the VM VFS and drivers people in one room and see
> if we can have a Linux solution to this problem
> 
> Boaz
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