thp: compound_lock

Add a new compound_lock() needed to serialize put_page against
__split_huge_page_refcount().

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 57e11b2a18ba..3b1754ad8785 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -14,6 +14,7 @@
 #include <linux/mm_types.h>
 #include <linux/range.h>
 #include <linux/pfn.h>
+#include <linux/bit_spinlock.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -305,6 +306,39 @@ static inline int is_vmalloc_or_module_addr(const void *x)
 }
 #endif
 
+static inline void compound_lock(struct page *page)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        bit_spin_lock(PG_compound_lock, &page->flags);
+#endif
+}
+
+static inline void compound_unlock(struct page *page)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        bit_spin_unlock(PG_compound_lock, &page->flags);
+#endif
+}
+
+static inline unsigned long compound_lock_irqsave(struct page *page)
+{
+        unsigned long uninitialized_var(flags);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        local_irq_save(flags);
+        compound_lock(page);
+#endif
+        return flags;
+}
+
+static inline void compound_unlock_irqrestore(struct page *page,
+                                              unsigned long flags)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        compound_unlock(page);
+        local_irq_restore(flags);
+#endif
+}
+
 static inline struct page *compound_head(struct page *page)
 {
         if (unlikely(PageTail(page)))