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-rw-r--r--mm/highmem.c65
1 files changed, 57 insertions, 8 deletions
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)