linux-kernel - Re: [PATCHv3 2/2] mm: implement ->map

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Date:	Wed, 2 Apr 2014 22:07:09 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Dave Chinner <david@...morbit.com>, Ning Qu <quning@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 2/2] mm: implement ->map_pages for page cache

On Wed, Apr 02, 2014 at 10:03:24PM +0400, Konstantin Khlebnikov wrote:
> > +void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
> > +{
> > +       struct radix_tree_iter iter;
> > +       void **slot;
> > +       struct file *file = vma->vm_file;
> > +       struct address_space *mapping = file->f_mapping;
> > +       loff_t size;
> > +       struct page *page;
> > +       unsigned long address = (unsigned long) vmf->virtual_address;
> > +       unsigned long addr;
> > +       pte_t *pte;
> > +
> > +       rcu_read_lock();
> > +       radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, vmf->pgoff) {
> > +               if (iter.index > vmf->max_pgoff)
> > +                       break;
> > +repeat:
> > +               page = radix_tree_deref_slot(slot);
> 
> Here is obvious race with memory reclaimer/truncate. Pointer to page
> might become NULL.

Thanks for noticing that. It has been fixed in -mm already.

-- 
 Kirill A. Shutemov
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