linux-kernel - Re: [PATCH] Call flush_dcache_page around PIO data transfers in libata-aff.c

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Date:	Wed, 03 Mar 2010 11:18:25 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Garzik <jgarzik@...ox.com>
Subject: Re: [PATCH] Call flush_dcache_page around PIO data transfers in
 libata-aff.c

On Wed, 2010-03-03 at 08:24 +0000, Sebastian Andrzej Siewior wrote:
> > drivers/ata/libata-sff.c |    6 ++++++
> > 1 files changed, 6 insertions(+), 0 deletions(-)
> >
> >diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
> >index 741065c..3d3c854 100644
> >--- a/drivers/ata/libata-sff.c
> >+++ b/drivers/ata/libata-sff.c
> >@@ -893,6 +896,9 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
> >                                      do_write);
> >       }
> >
> >+      if (!do_write)
> >+              flush_dcache_page(page);
> >+
> >       qc->curbytes += qc->sect_size;
> >       qc->cursg_ofs += qc->sect_size;
> 
> That part got merged and it leads to a BUG if CONFIG_DEBUG_VM is
> enabled. My mips box and arm use page_mapping() in flush_dcache_page()
> which has VM_BUG_ON(PageSlab(page)) in it.
> 
> Any comments on that?

There is a long thread on USB HCD and cache coherency on ARM which I
started pretty much at the same time with the libata-sff change. I need
to do some testing but in the view of the discussions in the other
thread, we may not need this patch at all:

http://thread.gmane.org/gmane.linux.usb.general/27072

Basically, the meaning of PG_arch_1 should be page clean rather than
page dirty.

-- 
Catalin

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