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Subject: Re: AZFS file system proposal
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: Maxim Shchetynin <maxim@linux.vnet.ibm.com>
Cc: linux-fsdevel@vger.kernel.org, linuxppc-dev@ozlabs.org,
       linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>
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Date: Wed, 09 Jul 2008 19:23:34 +1000
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On Wed, 2008-07-09 at 11:14 +0200, Maxim Shchetynin wrote:
> Am Wed, 09 Jul 2008 18:58:38 +1000
> schrieb Benjamin Herrenschmidt <benh@kernel.crashing.org>:
> 
> > On Tue, 2008-07-01 at 16:59 +0200, Arnd Bergmann wrote:
> > > I wouldn't hold up merging the file system for this problem, but
> > > until it is solved, the Kconfig entry should probably have
> > > a "depends on PPC".
> > 
> > Better, use an ifdef for powerpc flags, and #else to pgprot_noncached.
> 
> Thank you Ben. Then, how about this?
> 
> azfs_mmap(struct file *file, struct vm_area_struct *vma)
> {
> ...
> ...
> ...
> #ifdef CONFIG_PPC
> 	pgprot_t page_prot;
> #endif
> ...
> ...
> ...
> #ifdef CONFIG_PPC
> 	page_prot = pgprot_val(vma->vm_page_prot);
> 	page_prot |= (_PAGE_NO_CACHE | _PAGE_RW);
> 	page_prot &= ~_PAGE_GUARDED;
> 	vma->vm_page_prot = __pgprot(page_prot);
> #else
> 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> #endif
> ...

I'd rather do

	pgprot_t  prot;

#ifdef CONFIG_PPC
	prot = <whatever>
#else
	prot = pgprot_noncached(...)
#endif
	vma->vm_page_prot = prot;

To limit the number of ifdef's

Cheers,
Ben.


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