Re: [patch][9/9] block: remove bio walking

[Jens Axboe]

On Thu, Sep 09 2004, Russell King wrote:
> Essentially, kernel PIO writes data into the page cache, and that action
> may leave data in the CPU's caches.  Since the kernels mappings may not
> be coherent with mappings in userspace, data written to the kernel
> mappings may remain in the data cache, and stale data would be visible
> to user space.
> 
> There has been talk about using flush_dcache_page() to resolve
> this issue, but I'm not sure what the outcome was.  Certainly
> flush_dcache_page() is supposed to be used before the data in the
> kernels page cache is read or written.

Have you ever tested bouncing on arm? It seems to be lacking a
flush_dcache_page() indeed, how does this look?

===== mm/highmem.c 1.51 vs edited =====
--- 1.51/mm/highmem.c	2004-07-29 06:58:32 +02:00
+++ edited/mm/highmem.c	2004-09-09 17:44:14 +02:00
@@ -301,6 +301,7 @@
 		vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 
 		bounce_copy_vec(tovec, vfrom);
+		flush_dcache_page(tovec->bv_page);
 	}
 }
 

-- 
Jens Axboe

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