Re: [rfc patch 2/2] direct-io: remove address alignment check

[Daniel McNeil <daniel@osdl.org>]

On Thu, 2005-07-14 at 11:23, Andi Kleen wrote:
> > That is exactly why I made this a separate patch, so that we
> > can test and find out where the problems are and work to fix
> > them.
> 
> That's pretty hard because there are a lot of block drivers.
> 
> And might not very nice for people's data.
> 
> > 
> > Are there problems only with odd sizes, or do drivers have problems
> > with non-512 sizes?
> 
> I believe they have problems with non 512 sizes (and probably alignments) 
> too.

The check still only allows i/o that is multiple of the device block
size.  That will always be a requirement.

I was trying to ask:
Do drivers have problems with odd addresses or with
non-512 addresses?

In my limited testing, I saw problems with odd user space
addresses on IDE (using DMA).  When testing 2-byte aligned
addresses, I did not see any problems, and so far, the data
looks correct.

I am continuing to test and this patch allows other to try
it out as well.  For the most part, it should be safe because
nobody has application code that uses O_DIRECT with non-aligned
addresses.  Obviously, it will only be ready for mainline
if/when we fix all the drivers.

Thanks,

Daniel

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