writeback: fix ppc compile warnings on do_div(long long, unsigned long)

Fix powerpc compile warnings

mm/page-writeback.c: In function 'bdi_position_ratio':
mm/page-writeback.c:622:3: warning: comparison of distinct pointer types lacks a cast [enabled by default]
page-writeback.c:635:4: warning: comparison of distinct pointer types lacks a cast [enabled by default]

Also fix gcc "uninitialized var" warnings.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 325f753c80ed..0802d5177997 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -618,8 +618,8 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
         x_intercept = bdi_setpoint + span;
 
         if (bdi_dirty < x_intercept - span / 4) {
-                pos_ratio *= x_intercept - bdi_dirty;
-                do_div(pos_ratio, x_intercept - bdi_setpoint + 1);
+                pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
+                                    x_intercept - bdi_setpoint + 1);
         } else
                 pos_ratio /= 4;
 
@@ -630,10 +630,9 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
          */
         x_intercept = bdi_thresh / 2;
         if (bdi_dirty < x_intercept) {
-                if (bdi_dirty > x_intercept / 8) {
-                        pos_ratio *= x_intercept;
-                        do_div(pos_ratio, bdi_dirty);
-                } else
+                if (bdi_dirty > x_intercept / 8)
+                        pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
+                else
                         pos_ratio *= 8;
         }
 
@@ -1010,10 +1009,10 @@ static void balance_dirty_pages(struct address_space *mapping,
         unsigned long dirty_thresh;
         unsigned long bdi_thresh;
         long pause = 0;
-        long max_pause;
+        long uninitialized_var(max_pause);
         bool dirty_exceeded = false;
         unsigned long task_ratelimit;
-        unsigned long dirty_ratelimit;
+        unsigned long uninitialized_var(dirty_ratelimit);
         unsigned long pos_ratio;
         struct backing_dev_info *bdi = mapping->backing_dev_info;
         unsigned long start_time = jiffies;