On Mon, 2009-06-22 at 17:46 +0100, Russell King - ARM Linux wrote:On Mon, Jun 22, 2009 at 05:13:16PM +0100, Catalin Marinas wrote:In my case (ext2 over pata_platform), there is no flush_dcache_page()As already covered, there's no chance of adding such a call to the
call after the page was written with data from the CompactFlash (neither
the driver nor the VFS layer do this and we used hardware tracing to
double-check). When the page is mapped into user space,
update_mmu_cache() is called but the page hasn't been marked as dirty
and no D-cache flushing occurs. Calling flush_dcache_page() in
mpage_end_io_read() works around this issue.
generic kernel. It's the responsibility of the drivers to ensure that
data they read in hits the underlying page - in the same way that DMA
does.
The patch below appears to solve the problem with CompactFlash using
pata_platform (I cc'ed linux-ide since the patch changes their code).
The patch only handles the read case but similarly it may need to handle
the write case if D-cache aliasing between user and kernel mappings
exists.
For the USB mass storage, I haven't yet figured out the best place to
call flush_dcache_page().