[PATCH] balance_dirty_pages_ratelimited: take nr_pages arg

Modify balance_dirty_pages_ratelimited() so that it can take a
number-of-pages-which-I-just-dirtied argument.  For msync().

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 24 insertions, 10 deletions

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 609565961494..56f92fcbe94a 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -99,7 +99,15 @@ int dirty_writeback_centisecs_handler(struct ctl_table *, int, struct file *,
                                       void __user *, size_t *, loff_t *);
 
 void page_writeback_init(void);
-void balance_dirty_pages_ratelimited(struct address_space *mapping);
+void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
+                                        unsigned long nr_pages_dirtied);
+
+static inline void
+balance_dirty_pages_ratelimited(struct address_space *mapping)
+{
+        balance_dirty_pages_ratelimited_nr(mapping, 1);
+}
+
 int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 int sync_page_range(struct inode *inode, struct address_space *mapping,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c1052ee79f01..c67ddc464721 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -256,8 +256,9 @@ static void balance_dirty_pages(struct address_space *mapping)
 }
 
 /**
- * balance_dirty_pages_ratelimited - balance dirty memory state
+ * balance_dirty_pages_ratelimited_nr - balance dirty memory state
  * @mapping: address_space which was dirtied
+ * @nr_pages: number of pages which the caller has just dirtied
  *
  * Processes which are dirtying memory should call in here once for each page
  * which was newly dirtied.  The function will periodically check the system's
@@ -268,10 +269,12 @@ static void balance_dirty_pages(struct address_space *mapping)
  * limit we decrease the ratelimiting by a lot, to prevent individual processes
  * from overshooting the limit by (ratelimit_pages) each.
  */
-void balance_dirty_pages_ratelimited(struct address_space *mapping)
+void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
+                                        unsigned long nr_pages_dirtied)
 {
-        static DEFINE_PER_CPU(int, ratelimits) = 0;
-        long ratelimit;
+        static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
+        unsigned long ratelimit;
+        unsigned long *p;
 
         ratelimit = ratelimit_pages;
         if (dirty_exceeded)
@@ -281,15 +284,18 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
          * Check the rate limiting. Also, we do not want to throttle real-time
          * tasks in balance_dirty_pages(). Period.
          */
-        if (get_cpu_var(ratelimits)++ >= ratelimit) {
-                __get_cpu_var(ratelimits) = 0;
-                put_cpu_var(ratelimits);
+        preempt_disable();
+        p =  &__get_cpu_var(ratelimits);
+        *p += nr_pages_dirtied;
+        if (unlikely(*p >= ratelimit)) {
+                *p = 0;
+                preempt_enable();
                 balance_dirty_pages(mapping);
                 return;
         }
-        put_cpu_var(ratelimits);
+        preempt_enable();
 }
-EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
+EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
 
 void throttle_vm_writeout(void)
 {