Andrew Morton wrote:
On Tue, 6 Feb 2007 09:02:11 +0100 (CET) Nick Piggin <npiggin@xxxxxxx> wrote:
+static inline void __SetPageUptodate(struct page *page)
+{
+#ifdef CONFIG_S390
if (!test_and_set_bit(PG_uptodate, &page->flags))
page_test_and_clear_dirty(page);
-}
#else
-#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags)
+ /*
+ * Memory barrier must be issued before setting the PG_uptodate bit,
+ * so all previous writes that served to bring the page uptodate are
+ * visible before PageUptodate becomes true.
+ *
+ * S390 is guaranteed to have a barrier in the test_and_set operation
+ * (see Documentation/atomic_ops.txt).
+ *
+ * XXX: does this memory barrier need to be anything special to
+ * handle things like DMA writes into the page?
+ */
+ smp_wmb();
+ set_bit(PG_uptodate, &(page)->flags);
#endif
+}
+
+static inline void SetPageUptodate(struct page *page)
+{
+ WARN_ON(!PageLocked(page));
+ __SetPageUptodate(page);
+}
+
+static inline void SetNewPageUptodate(struct page *page)
+{
+ __SetPageUptodate(page);
+}
I was panicing for a minute when I saw that __SetPageUptodate() in there.
Conventionally the __SetPageFoo namespace is for nonatomic updates to
page->flags. Can we call this something different?
Duh, of course, sorry.
What a fugly patchset :(
Fugly problem. One could fix it by always locking the page, but I was
worried about Hugh flaming me if I tried that ;)
--
SUSE Labs, Novell Inc.
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