Messages in this thread | | | Date | Wed, 23 Jun 2004 20:59:06 +0900 (JST) | Subject | Re: Atomic operation for physically moving a page (for memory defragmentation) | From | Hirokazu Takahashi <> |
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Hi,
> > > However, if we're on an unlikely error path or > > > similar and other options aren't suitable... > > > > Maintaining atomicity in uniprocessor systems is easy > > by preempt_enable and preempt_disable during the > > operation. This implementation cannot be used for SMP > > systems. > > Now during the time a page is copied/updatede if a > > page is accessed the copied contents become invalid, > > as updation is not done. Also during updation a > > similar situation might arise. > > The problem we are facing is to maintain the atomicity > > of this operation on SMP boxes. > > I think what you really want to do is keep anybody else from making a > new pte to the page, once you've invalidated all of the existing ones, > right? > > Holding a lock_page() should do the trick. Anybody that goes any pulls > the page out of the page cache has to do a lock_page() and check > page->mapping before they can establish a pte to it, so you can stop > that. Since you're invalidating page->mapping before you move the page > (you *are* doing this, right?), it will end up working itself out.
We should know that many part of kernel code will access the page without holding a lock_page(). The lock_page() can't block them.
Thank you, Hirokazu Takahashi. - 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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