On Wed, 2010-12-01 at 15:46 -0800, Andrew Morton wrote:
quoted text
> On Wed, 01 Dec 2010 18:21:16 -0500
> Trond Myklebust <Trond.Myklebust@netapp.com> wrote:
> 
> > --- a/mm/truncate.c
> > +++ b/mm/truncate.c
> > @@ -108,6 +108,10 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
> >  	clear_page_mlock(page);
> >  	remove_from_page_cache(page);
> >  	ClearPageMappedToDisk(page);
> > +
> > +	if (mapping->a_ops->freepage)
> > +		mapping->a_ops->freepage(page);
> > +
> >  	page_cache_release(page);	/* pagecache ref */
> >  	return 0;
> >  }
> 
> So here we're assuming that `mapping' was pinned by other means.
> 
> Fair enough, although subtle.  Even drop_pagecache_sb() got it right ;)
> 
> > @@ -390,6 +394,10 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
> >  	__remove_from_page_cache(page);
> >  	spin_unlock_irq(&mapping->tree_lock);
> >  	mem_cgroup_uncharge_cache_page(page);
> > +
> > +	if (mapping->a_ops->freepage)
> > +		mapping->a_ops->freepage(page);
> > +
> >  	page_cache_release(page);	/* pagecache ref */
> >  	return 1;
> >  failed:
> 
> And here.

Yes. Both these functions are static, and their callers are assuming
that something is already pinning the underlying inode, so the above
should be quite safe.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

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