Messages in this thread | | | Date | Mon, 9 Oct 2006 14:14:17 +0200 | From | Nick Piggin <> | Subject | Re: [patch 3/3] mm: fault handler to replace nopage and populate |
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On Mon, Oct 09, 2006 at 10:07:50PM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2006-10-09 at 13:58 +0200, Nick Piggin wrote: > > > > The VM won't see that you have struct pages backing the ptes, and won't > > do the right refcounting or rmap stuff... But for file backed mappings, > > all the critical rmap stuff should be set up at mmap time, so you might > > have another option to simply always do the nopfn thing, as far as the > > VM is concerned (ie. even when you do have a struct page) > > Any reason why it wouldn't work to flip that bit on the first no_page() > after a migration ? A migration always involves destroying all PTEs and > is done with a per-object mutex held that no_page() takes too, so we can > be pretty sure that the first nopage can set that bit before any PTE is > actually inserted in the mapping after all the previous ones have been > invalidated... That would avoid having to walk the vma's.
Ok I guess that would work. I was kind of thinking that one needs to hold the mmap_sem for writing when changing the flags, but so long as everyone *else* does, then I guess you can get exclusion from just the read lock. And your per-object mutex would prevent concurrent nopages from modifying it. - 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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