USB mass storage and ARM cache coherency

[Benjamin Herrenschmidt]

On Fri, 2010-02-26 at 16:00 +0000, Catalin Marinas wrote:
> > I'm surprised that usb-storage has an issue here. It shouldn't
> afaik,
> > since it's just a SCSI driver (or not anymore ?) and the BIO or
> > filesystems handle things there no ? I haven't seen a single call to
> > flush_dcache_page() in any of drivers/scsi, drivers/ata or
> drivers/ide
> > when I looked...
> 
> The BIO or filesystem code don't call flush_dcache_page() either (well
> some do like cramfs or jffs but they decompress the data received from
> the block device). 

That's weird... that would mean that all existing PIO IDE or SCSI is
broken etc... Including I$/D$ cache coherency on powerpc and more. That
surprises me :-)

On an older kernel tree here:

$ grep -r flush_dcache_page fs | wc -l
118

So maybe that's where things need fixing ?

Cheers,
Ben.