linux-kernel - Re: [PATCH 13/14] Pramfs: Write Protection

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Date:	Thu, 18 Jun 2009 11:57:36 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Marco <marco.stornelli@...il.com>
Cc:	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	linux@....linux.org.uk, linux-m68k@...ts.linux-m68k.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Linux Embedded <linux-embedded@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Daniel Walker <dwalker@....ucsc.edu>
Subject: Re: [PATCH 13/14] Pramfs: Write Protection

On Wed, Jun 17, 2009 at 06:58:00PM +0200, Marco wrote:
> Jared Hulbert wrote:
> > > Why not just fix flush_tlb_range()?
> > > 
> > > If an arch has a flush_tlb_kernel_page() that works then it stands to
> > > reason that the flush_tlb_kernel_range() shouldn't work with minimal
> > > effort, no?
> > 
> > flush_tlb_kernel_page() is a new one to me, it doesn't have any mention
> > in Documentation/cachetlb.txt anyways.
> > 
> > Many of the flush_tlb_kernel_range() implementations do ranged checks
> > with tunables to determine whether it is more expensive to selectively
> > flush vs just blowing the entire TLB away.
> > 
> > Likewise, there is no reason why those 4 architectures can not just shove
> > that if (end <= start + PAGE_SIZE) check in the beginning of their
> > flush_tlb_kernel_range() and fall back on flush_tlb_kernel_page() for
> > those cases. Hiding this in generic code is definitely not the way to go.
> 
> Ok I'll change that function at arch level and I'll remove the ifdef,
> I'll call only flush_tlb_kernel_page(), but I'd like to know what is
> the opinion of the arch maintainers to do that.  (Who is the maintainer
> of H8300 arch?)
> 
No, you should call flush_tlb_kernel_range() and just fix up the
flush_tlb_kernel_range() calls to wrap in to flush_tlb_kernel_page(). As
far as the kernel is concerned, flush_tlb_kernel_page() is not a standard
interface, as it has no mention in Documentation/cachetlb.txt.
flush_tlb_page() and flush_tlb_kernel_range() on the other hand are both
standard interfaces.

H8300 is a nommu platform, so it has no TLB to flush. Yoshinori Sato is
the maintainer. Consult the MAINTAINERS file, that's what it is there for.
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