From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: Re: problems in commit 2d4dc890b5c8 (block: add helpers to run
 flush_dcache_page() against a bio and a request's pages)
Date: Thu, 10 Dec 2009 14:28:04 -0600
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To: Ilya Loginov <isloginov@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>, linux-arch@vger.kernel.org

On Thu, 2009-12-10 at 22:46 +0300, Ilya Loginov wrote:
> On Thu, 10 Dec 2009 11:07:31 -0600
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > What MTD device is this?  The subsystem is very complex, but I suppose I
> > could trace the read path in a single device to see what the actual
> > problem is.
> 
> Oh! There is a FPGA. There are kernel and diskimage(via slram) in memory.
> So, kernel just copy a part of libc from fs in RAM to RAM.

Right, so this is the problem.  Where you do the ram to ram copy
in-kernel, you need kmap/kunmap.  If you copy from the FPGA RAM to the
kernel RAM, before you do the kunmap, you also need a
flush_kernel_dcache_page().  This (plus implementing
flush_kernel_dcache_page() on mips) will fix all coherency issues.

Which exact driver in drivers/mtd?  I can probably just look at it and
see where the kmap/flush is supposed to be.

James