diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index 4208f94d93f7..7b3b04ba60f3 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -67,8 +67,6 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,
 
 extern void debug_dma_dump_mappings(struct device *dev);
 
-extern void debug_dma_assert_idle(struct page *page);
-
 #else /* CONFIG_DMA_API_DEBUG */
 
 static inline void dma_debug_add_bus(struct bus_type *bus)
@@ -157,10 +155,6 @@ static inline void debug_dma_dump_mappings(struct device *dev)
 {
 }
 
-static inline void debug_dma_assert_idle(struct page *page)
-{
-}
-
 #endif /* CONFIG_DMA_API_DEBUG */
 
 #endif /* __DMA_DEBUG_H */
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index f4770fcfa62b..5732b2b3ef17 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -186,11 +186,6 @@ config DMA_API_DEBUG
 	  drivers like double-freeing of DMA mappings or freeing mappings that
 	  were never allocated.
 
-	  This also attempts to catch cases where a page owned by DMA is
-	  accessed by the cpu in a way that could cause data corruption.  For
-	  example, this enables cow_user_page() to check that the source page is
-	  not undergoing DMA.
-
 	  This option causes a performance degradation.  Use only if you want to
 	  debug device drivers and dma interactions.
 
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 6f4f4b9d2d03..8e9f7b301c6d 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -448,9 +448,6 @@ void debug_dma_dump_mappings(struct device *dev)
  * dma_active_cacheline entry to track per event.  dma_map_sg(), on the
  * other hand, consumes a single dma_debug_entry, but inserts 'nents'
  * entries into the tree.
- *
- * At any time debug_dma_assert_idle() can be called to trigger a
- * warning if any cachelines in the given page are in the active set.
  */
 static RADIX_TREE(dma_active_cacheline, GFP_NOWAIT);
 static DEFINE_SPINLOCK(radix_lock);
@@ -497,10 +494,7 @@ static void active_cacheline_inc_overlap(phys_addr_t cln)
 	overlap = active_cacheline_set_overlap(cln, ++overlap);
 
 	/* If we overflowed the overlap counter then we're potentially
-	 * leaking dma-mappings.  Otherwise, if maps and unmaps are
-	 * balanced then this overflow may cause false negatives in
-	 * debug_dma_assert_idle() as the cacheline may be marked idle
-	 * prematurely.
+	 * leaking dma-mappings.
 	 */
 	WARN_ONCE(overlap > ACTIVE_CACHELINE_MAX_OVERLAP,
 		  pr_fmt("exceeded %d overlapping mappings of cacheline %pa\n"),
@@ -555,44 +549,6 @@ static void active_cacheline_remove(struct dma_debug_entry *entry)
 	spin_unlock_irqrestore(&radix_lock, flags);
 }
 
-/**
- * debug_dma_assert_idle() - assert that a page is not undergoing dma
- * @page: page to lookup in the dma_active_cacheline tree
- *
- * Place a call to this routine in cases where the cpu touching the page
- * before the dma completes (page is dma_unmapped) will lead to data
- * corruption.
- */
-void debug_dma_assert_idle(struct page *page)
-{
-	struct dma_debug_entry *entry;
-	unsigned long pfn;
-	phys_addr_t cln;
-
-	if (dma_debug_disabled())
-		return;
-
-	if (!page)
-		return;
-
-	pfn = page_to_pfn(page);
-	cln = (phys_addr_t) pfn << CACHELINE_PER_PAGE_SHIFT;
-
-	rcu_read_lock();
-	if (!radix_tree_gang_lookup(&dma_active_cacheline, (void **) &entry,
-				    cln, 1) || entry->pfn != pfn)
-		entry = NULL;
-	rcu_read_unlock();
-
-	if (!entry)
-		return;
-
-	cln = to_cacheline_number(entry);
-	err_printk(entry->dev, entry,
-		   "cpu touching an active dma mapped cacheline [cln=%pa]\n",
-		   &cln);
-}
-
 /*
  * Wrapper function for adding an entry to the hash.
  * This function takes care of locking itself.
diff --git a/mm/memory.c b/mm/memory.c
index 228efaca75d3..d3c3bbd65a7e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2411,8 +2411,6 @@ static inline bool cow_user_page(struct page *dst, struct page *src,
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long addr = vmf->address;
 
-	debug_dma_assert_idle(src);
-
 	if (likely(src)) {
 		copy_user_highpage(dst, src, addr, vma);
 		return true;