Messages in this thread | | | Date | Sun, 25 Sep 2005 23:14:24 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 04/21] mm: zap_pte_range dont dirty anon |
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Hugh Dickins <hugh@veritas.com> wrote: > > > What is the page is (for example) clean swapcache, having been recently > > faulted in. If this pte indicates that this process has modified the page > > and we don't run set_page_dirty(), the page could be reclaimed and the > > change is lost. > > Absolutely. But either the page is unique to this mm, shared only with > swapcache: in which case we're about to do a free_swap_cache on it (that > may be delayed in actually freeing the swap because of not getting page > lock, presumably because vmscan just got to it, but no matter), and we > don't care at all that the page no longer represents what's on swap disk. > > Or, the page is shared with another mm. But it's an anonymous page > (a private page), so it's shared via fork, and COW applies to it.
mmap(MAP_ANONYMOUS|MAP_SHARED) fork() swapout swapin swapoff
Now we have two mm's sharing a clean, non-cowable, non-swapcache anonymous page, no? - 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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