1 files changed, 75 insertions, 11 deletions

diff --git a/mm/highmem.c b/mm/highmem.c
index b32b70cdaed6..123bcd3ed4f2 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -44,6 +44,66 @@ DEFINE_PER_CPU(int, __kmap_atomic_idx);
  */
 #ifdef CONFIG_HIGHMEM
 
+/*
+ * Architecture with aliasing data cache may define the following family of
+ * helper functions in its asm/highmem.h to control cache color of virtual
+ * addresses where physical memory pages are mapped by kmap.
+ */
+#ifndef get_pkmap_color
+
+/*
+ * Determine color of virtual address where the page should be mapped.
+ */
+static inline unsigned int get_pkmap_color(struct page *page)
+{
+        return 0;
+}
+#define get_pkmap_color get_pkmap_color
+
+/*
+ * Get next index for mapping inside PKMAP region for page with given color.
+ */
+static inline unsigned int get_next_pkmap_nr(unsigned int color)
+{
+        static unsigned int last_pkmap_nr;
+
+        last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
+        return last_pkmap_nr;
+}
+
+/*
+ * Determine if page index inside PKMAP region (pkmap_nr) of given color
+ * has wrapped around PKMAP region end. When this happens an attempt to
+ * flush all unused PKMAP slots is made.
+ */
+static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
+{
+        return pkmap_nr == 0;
+}
+
+/*
+ * Get the number of PKMAP entries of the given color. If no free slot is
+ * found after checking that many entries, kmap will sleep waiting for
+ * someone to call kunmap and free PKMAP slot.
+ */
+static inline int get_pkmap_entries_count(unsigned int color)
+{
+        return LAST_PKMAP;
+}
+
+/*
+ * Get head of a wait queue for PKMAP entries of the given color.
+ * Wait queues for different mapping colors should be independent to avoid
+ * unnecessary wakeups caused by freeing of slots of other colors.
+ */
+static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
+{
+        static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
+
+        return &pkmap_map_wait;
+}
+#endif
+
 unsigned long totalhigh_pages __read_mostly;
 EXPORT_SYMBOL(totalhigh_pages);
 
@@ -68,13 +128,10 @@ unsigned int nr_free_highpages (void)
 }
 
 static int pkmap_count[LAST_PKMAP];
-static unsigned int last_pkmap_nr;
 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
 
 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
@@ -161,15 +218,17 @@ static inline unsigned long map_new_virtual(struct page *page)
 {
         unsigned long vaddr;
         int count;
+        unsigned int last_pkmap_nr;
+        unsigned int color = get_pkmap_color(page);
 
 start:
-        count = LAST_PKMAP;
+        count = get_pkmap_entries_count(color);
         /* Find an empty entry */
         for (;;) {
-                last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
-                if (!last_pkmap_nr) {
+                last_pkmap_nr = get_next_pkmap_nr(color);
+                if (no_more_pkmaps(last_pkmap_nr, color)) {
                         flush_all_zero_pkmaps();
-                        count = LAST_PKMAP;
+                        count = get_pkmap_entries_count(color);
                 }
                 if (!pkmap_count[last_pkmap_nr])
                         break;  /* Found a usable entry */
@@ -181,12 +240,14 @@ start:
                  */
                 {
                         DECLARE_WAITQUEUE(wait, current);
+                        wait_queue_head_t *pkmap_map_wait =
+                                get_pkmap_wait_queue_head(color);
 
                         __set_current_state(TASK_UNINTERRUPTIBLE);
-                        add_wait_queue(&pkmap_map_wait, &wait);
+                        add_wait_queue(pkmap_map_wait, &wait);
                         unlock_kmap();
                         schedule();
-                        remove_wait_queue(&pkmap_map_wait, &wait);
+                        remove_wait_queue(pkmap_map_wait, &wait);
                         lock_kmap();
 
                         /* Somebody else might have mapped it while we slept */
@@ -274,6 +335,8 @@ void kunmap_high(struct page *page)
         unsigned long nr;
         unsigned long flags;
         int need_wakeup;
+        unsigned int color = get_pkmap_color(page);
+        wait_queue_head_t *pkmap_map_wait;
 
         lock_kmap_any(flags);
         vaddr = (unsigned long)page_address(page);
@@ -299,13 +362,14 @@ void kunmap_high(struct page *page)
                  * no need for the wait-queue-head's lock.  Simply
                  * test if the queue is empty.
                  */
-                need_wakeup = waitqueue_active(&pkmap_map_wait);
+                pkmap_map_wait = get_pkmap_wait_queue_head(color);
+                need_wakeup = waitqueue_active(pkmap_map_wait);
         }
         unlock_kmap_any(flags);
 
         /* do wake-up, if needed, race-free outside of the spin lock */
         if (need_wakeup)
-                wake_up(&pkmap_map_wait);
+                wake_up(pkmap_map_wait);
 }
 
 EXPORT_SYMBOL(kunmap_high);