linux-kernel - RE: [PATCH] Cachefiles, mpage_cleardirty addtition, west bridgerelated

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Date:	Wed, 8 Sep 2010 10:02:49 -0700
From:	"David Cross" <david.cross@...ress.com>
To:	"'Greg KH'" <greg@...ah.com>
Cc:	<dhowells@...hat.com>, <linux-cachefs@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] Cachefiles, mpage_cleardirty addtition, west bridgerelated


> -----Original Message-----
> From: Greg KH [mailto:greg@...ah.com] 

> On Tue, Sep 07, 2010 at 12:33:31PM -0700, David Cross wrote:
> > This patch adds the mpage_cleardirty function to the cachefiles
implementation in the kernel.
> > The purpose behind this patch is to allow for file based DMA through an
external DMA engine
> > without the data ever going through the process. The procedure for the
usage of this function 
> > is as follows:
> > 1) User space allocates and maps a file
> > 2) external DMA device transfers the data to non-volatile storage
directly without it going through 
> >    the processor
> > 3) the "dirty" pages must be cleared and invalidated as they do not
contain correct information.
> > 
> > I believe that David is the correct maintainer and am hoping that he is
willing to ACK this change. Please let me know 
> > if there are any issues or concerns with this patch or if I should be
> > asking a different maintainer to ack.
> > Thanks,
> > David
> > 
> > Signed-off-by: David Cross <david.cross@...ress.com>
> > 
> > diff -uprN -X linux-next-vanilla/Documentation/dontdiff
linux-next-vanilla/fs/mpage.c linux-next-incl-sdk/fs/mpage.c
> > --- linux-next-vanilla/fs/mpage.c	2010-08-31 19:32:51.000000000 -0700
> > +++ linux-next-incl-sdk/fs/mpage.c	2010-09-07 11:52:39.000000000 -0700
> > @@ -716,3 +716,50 @@ int mpage_writepage(struct page *page, g
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(mpage_writepage);
> > +
> > +int mpage_cleardirty(struct address_space *mapping, int num_pages)
> > +{
> > +	int ret = 0;
> > +	int nr_pages;
> > +	struct pagevec pvec;
> > +	pgoff_t index = 0;
> > +	pgoff_t end;
> > +
> > +	pagevec_init(&pvec, 0);
> > +	index = mapping->writeback_index;
> > +	end = index + num_pages;
> > +
> > +	while ((index <= end) &&
> > +	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
> > +				PAGECACHE_TAG_DIRTY, min(end - index,
> > +					(pgoff_t)PAGEVEC_SIZE-1) + 1))) {
> > +		unsigned i;
> > +
> > +		for (i = 0; i < nr_pages; i++) {
> > +			struct page *page = pvec.pages[i];
> > +
> > +			lock_page(page);
> > +			ret = clear_page_dirty_for_io(page);
> > +			if (page_has_private(page))
> > +				do_invalidatepage(page, 0);
> > +
> > +			cancel_dirty_page(page, PAGE_CACHE_SIZE);
> > +
> > +			remove_from_page_cache(page);
> > +			ClearPageMappedToDisk(page);
> > +			page_cache_release(page);	/* pagecache ref */
> > +			unlock_page(page);
> > +
> > +			if (!ret) {
> > +				printk(KERN_INFO "mpage_cleardirty: "
> > +				"clear_page_dirty_for_io returned %d\n",
ret);
> > +				return ret;
> > +			}
> > +		}
> > +		pagevec_release(&pvec);
> > +		cond_resched();
> > +	}
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(mpage_cleardirty);

> EXPORT_SYMBOL_GPL()?
Sure, but do I need to submit a new patch for this as well?

thanks,

david


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