On 12/23/2013 09:35 PM, Martin K. Petersen wrote:
"Christoph" == Christoph Hellwig <hch@xxxxxxxxxxxxx> writes:
Christoph> We have the block integrity code to support DIF/DIX in the
Christoph> the tree for about 5 and a half years, and we still don't
Christoph> have a single consumer of it.
What do you mean? If you have a DIX-capable HBA (lpfc, qla2xxx, zfcp)
then integrity protection is active from the block layer down. The only
code that's not currently being exercised are the tag interleaving
functions. I was hoping the FS people would use them for back pointers
but nobody seemed to bite.
Christoph> Given that we'll have a lot of work to do in this area with
Christoph> block multiqueue I think it's time to either kill it off for
Christoph> good or make sure we can actually use and test it.
I don't understand why multiqueue would require a lot of work? It's just
an extra scatterlist per request.
And obviously, if there's anything that needs to be done in this area
I'll be happy to do so...
One of the major knocks on linux file systems (except for btrfs) that I hear is
the lack of full data path checksums. DIF/DIX + xfs or ext4 done right will give
us another answer here. I don't think it will be common, it is a request that
comes in for very large storage customers most commonly.
We do have devices that support this and are working to get more vendor testing
done, so I would hate to see us throw out the code instead of fixing it up for
the end users that see value here.
I think that we can get this working & agree with the call to continue this
discussion (here and at LSF :))
Ric
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