linux-kernel - Re: [Lsf10-pc] [LFS/VM TOPIC] Stable pages while IO (was Wrong DIF guard tag on ext2 write)

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Message-ID: <20100604163009.GF10153@fieldses.org>
Date:	Fri, 4 Jun 2010 12:30:09 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Jan Kara <jack@...e.cz>
Cc:	Boaz Harrosh <bharrosh@...asas.com>,
	Vladislav Bolkhovitin <vst@...b.net>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Christof Schmitt <christof.schmitt@...ibm.com>,
	lsf10-pc@...ts.linuxfoundation.org,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-fsdevel@...r.kernel.org,
	Matthew Wilcox <willy@...ux.intel.com>,
	Ric Wheeler <rwheeler@...hat.com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [Lsf10-pc] [LFS/VM TOPIC] Stable pages while IO (was Wrong DIF
	guard tag on ext2 write)

On Fri, Jun 04, 2010 at 06:23:32PM +0200, Jan Kara wrote:
> On Thu 03-06-10 19:09:52, 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.
>   Hmm, I don't think it's really about "how to not let pages change" - that
> is doable by using wait_on_page_writeback() in ->page_mkwrite and
> ->write_begin.

Will the same work for the NFS server checksumming page data in read
replies?

--b.

> I think the discussion is more about whether we should do it
> or whether we should rechecksum and resubmit IO in case of checksum failure
> as Nick proposed...
> 
> 								Honza
> > People that care:
> > - Mirror and RAID people that need on disk consistency.
> > - Network storage that wants data checksum.
> > - 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
> -- 
> Jan Kara <jack@...e.cz>
> SUSE Labs, CR
> _______________________________________________
> Lsf10-pc mailing list
> Lsf10-pc@...ts.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/lsf10-pc
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