X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=mm%2Fhighmem.c;h=910198037bf59baa6649a75d1d632203483aa22b;hb=276e79ee6b3ff670dc9c041178da4b61af456a27;hp=b36b83b920ffe862f0d7060e29687c9bb998a0d8;hpb=31f297143b9905647fa5ef12086626a6f172a4ea;p=~andy%2Flinux

diff --git a/mm/highmem.c b/mm/highmem.c
index b36b83b920f..910198037bf 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -67,6 +67,25 @@ pte_t * pkmap_page_table;
 
 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
 
+/*
+ * Most architectures have no use for kmap_high_get(), so let's abstract
+ * the disabling of IRQ out of the locking in that case to save on a
+ * potential useless overhead.
+ */
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
+#define lock_kmap()             spin_lock_irq(&kmap_lock)
+#define unlock_kmap()           spin_unlock_irq(&kmap_lock)
+#define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
+#define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
+#else
+#define lock_kmap()             spin_lock(&kmap_lock)
+#define unlock_kmap()           spin_unlock(&kmap_lock)
+#define lock_kmap_any(flags)    \
+		do { spin_lock(&kmap_lock); (void)(flags); } while (0)
+#define unlock_kmap_any(flags)  \
+		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
+#endif
+
 static void flush_all_zero_pkmaps(void)
 {
 	int i;
@@ -113,9 +132,9 @@ static void flush_all_zero_pkmaps(void)
  */
 void kmap_flush_unused(void)
 {
-	spin_lock(&kmap_lock);
+	lock_kmap();
 	flush_all_zero_pkmaps();
-	spin_unlock(&kmap_lock);
+	unlock_kmap();
 }
 
 static inline unsigned long map_new_virtual(struct page *page)
@@ -145,10 +164,10 @@ start:
 
 			__set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&pkmap_map_wait, &wait);
-			spin_unlock(&kmap_lock);
+			unlock_kmap();
 			schedule();
 			remove_wait_queue(&pkmap_map_wait, &wait);
-			spin_lock(&kmap_lock);
+			lock_kmap();
 
 			/* Somebody else might have mapped it while we slept */
 			if (page_address(page))
@@ -184,29 +203,59 @@ void *kmap_high(struct page *page)
 	 * For highmem pages, we can't trust "virtual" until
 	 * after we have the lock.
 	 */
-	spin_lock(&kmap_lock);
+	lock_kmap();
 	vaddr = (unsigned long)page_address(page);
 	if (!vaddr)
 		vaddr = map_new_virtual(page);
 	pkmap_count[PKMAP_NR(vaddr)]++;
 	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
-	spin_unlock(&kmap_lock);
+	unlock_kmap();
 	return (void*) vaddr;
 }
 
 EXPORT_SYMBOL(kmap_high);
 
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
+/**
+ * kmap_high_get - pin a highmem page into memory
+ * @page: &struct page to pin
+ *
+ * Returns the page's current virtual memory address, or NULL if no mapping
+ * exists.  When and only when a non null address is returned then a
+ * matching call to kunmap_high() is necessary.
+ *
+ * This can be called from any context.
+ */
+void *kmap_high_get(struct page *page)
+{
+	unsigned long vaddr, flags;
+
+	lock_kmap_any(flags);
+	vaddr = (unsigned long)page_address(page);
+	if (vaddr) {
+		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
+		pkmap_count[PKMAP_NR(vaddr)]++;
+	}
+	unlock_kmap_any(flags);
+	return (void*) vaddr;
+}
+#endif
+
 /**
  * kunmap_high - map a highmem page into memory
  * @page: &struct page to unmap
+ *
+ * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
+ * only from user context.
  */
 void kunmap_high(struct page *page)
 {
 	unsigned long vaddr;
 	unsigned long nr;
+	unsigned long flags;
 	int need_wakeup;
 
-	spin_lock(&kmap_lock);
+	lock_kmap_any(flags);
 	vaddr = (unsigned long)page_address(page);
 	BUG_ON(!vaddr);
 	nr = PKMAP_NR(vaddr);
@@ -232,7 +281,7 @@ void kunmap_high(struct page *page)
 		 */
 		need_wakeup = waitqueue_active(&pkmap_map_wait);
 	}
-	spin_unlock(&kmap_lock);
+	unlock_kmap_any(flags);
 
 	/* do wake-up, if needed, race-free outside of the spin lock */
 	if (need_wakeup)