Messages in this thread | | | Date | Wed, 7 Mar 2007 03:34:00 -0800 | From | Andrew Morton <> | Subject | Re: [patch 8/6] mm: fix cpdfio vs fault race |
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On Wed, 7 Mar 2007 03:20:38 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:
> > > =================================================================== > > --- linux-2.6.orig/mm/memory.c > > +++ linux-2.6/mm/memory.c > > @@ -1676,6 +1676,17 @@ gotten: > > unlock: > > pte_unmap_unlock(page_table, ptl); > > if (dirty_page) { > > + /* > > + * Yes, Virginia, this is actually required to prevent a race > > + * with clear_page_dirty_for_io() from clearing the page dirty > > + * bit after it clear all dirty ptes, but before a racing > > + * do_wp_page installs a dirty pte. > > + * > > + * do_fault is protected similarly by holding the page lock > > + * after the dirty pte is installed. > > + */ > > + lock_page(dirty_page); > > + unlock_page(dirty_page); > > set_page_dirty_balance(dirty_page); > > put_page(dirty_page); > > Yes, I think that'll plug it. A wait_on_page_locked() should suffice.
Or will it? Suppose after the unlock_page() a _second_ clear_page_dirty_for_io() gets run - the same thing happens?
Extending the lock_page() coverage around the set_page_dirty() would prevent that.
I guess not needed - the second clear_page_dirty_for_io() will have cleaned the pte. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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