What an unpleasing patchset.  I really really hope we really have a bug in
there, and that all this crap isn't pointless uglification.

We _do_ need a flush_dcaceh_page() in all cases which you're concerned
about.  Perhaps we should stick the appropriate barriers in there.

On Thu, 15 Feb 2007 08:31:31 +0100 (CET) Nick Piggin [off-list ref] wrote:
+static inline void SetNewPageUptodate(struct page *page)
+{
+	/*
+	 * S390 sets page dirty bit on IO operations, which is why it is
+	 * cleared in SetPageUptodate. This is not an issue for newly
+	 * allocated pages that are brought uptodate by zeroing memory.
+	 */
+	smp_wmb();
+	__set_bit(PG_uptodate, &(page)->flags);
+}

__SetPageUptodate() might be more conventional.

Boy we'd better get the callers of this little handgrenade right.

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