writeback: make __wb_writeout_inc() and hard_dirty_limit() take wb_domaas a parameter

Currently __wb_writeout_inc() and hard_dirty_limit() assume
global_wb_domain; however, cgroup writeback support requires
considering per-memcg wb_domain too.

This patch separates out domain-specific part of __wb_writeout_inc()
into wb_domain_writeout_inc() which takes wb_domain as a parameter and
adds the parameter to hard_dirty_limit().  This will allow these two
functions to handle per-memcg wb_domains.

This patch doesn't introduce any behavioral changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 38d45d8c71f58ef41a86bd2e7ba06fc4c0d29b14..a4d0ceefd09730c536ea08dee86588870ed0ceec 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -445,17 +445,12 @@ static unsigned long wp_next_time(unsigned long cur_time)
        return cur_time;
 }
 
-/*
- * Increment the wb's writeout completion count and the global writeout
- * completion count. Called from test_clear_page_writeback().
- */
-static inline void __wb_writeout_inc(struct bdi_writeback *wb)
+static void wb_domain_writeout_inc(struct wb_domain *dom,
+                                  struct fprop_local_percpu *completions,
+                                  unsigned int max_prop_frac)
 {
-       struct wb_domain *dom = &global_wb_domain;
-
-       __inc_wb_stat(wb, WB_WRITTEN);
-       __fprop_inc_percpu_max(&dom->completions, &wb->completions,
-                              wb->bdi->max_prop_frac);
+       __fprop_inc_percpu_max(&dom->completions, completions,
+                              max_prop_frac);
        /* First event after period switching was turned off? */
        if (!unlikely(dom->period_time)) {
                /*
@@ -469,6 +464,17 @@ static inline void __wb_writeout_inc(struct bdi_writeback *wb)
        }
 }
 
+/*
+ * Increment @wb's writeout completion count and the global writeout
+ * completion count. Called from test_clear_page_writeback().
+ */
+static inline void __wb_writeout_inc(struct bdi_writeback *wb)
+{
+       __inc_wb_stat(wb, WB_WRITTEN);
+       wb_domain_writeout_inc(&global_wb_domain, &wb->completions,
+                              wb->bdi->max_prop_frac);
+}
+
 void wb_writeout_inc(struct bdi_writeback *wb)
 {
        unsigned long flags;
@@ -571,10 +577,9 @@ static unsigned long dirty_freerun_ceiling(unsigned long thresh,
        return (thresh + bg_thresh) / 2;
 }
 
-static unsigned long hard_dirty_limit(unsigned long thresh)
+static unsigned long hard_dirty_limit(struct wb_domain *dom,
+                                     unsigned long thresh)
 {
-       struct wb_domain *dom = &global_wb_domain;
-
        return max(thresh, dom->dirty_limit);
 }
 
@@ -744,7 +749,7 @@ static void wb_position_ratio(struct dirty_throttle_control *dtc)
        struct bdi_writeback *wb = dtc->wb;
        unsigned long write_bw = wb->avg_write_bandwidth;
        unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh);
-       unsigned long limit = hard_dirty_limit(dtc->thresh);
+       unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh);
        unsigned long wb_thresh = dtc->wb_thresh;
        unsigned long x_intercept;
        unsigned long setpoint;         /* dirty pages' target balance point */
@@ -1029,7 +1034,7 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc,
        struct bdi_writeback *wb = dtc->wb;
        unsigned long dirty = dtc->dirty;
        unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh);
-       unsigned long limit = hard_dirty_limit(dtc->thresh);
+       unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh);
        unsigned long setpoint = (freerun + limit) / 2;
        unsigned long write_bw = wb->avg_write_bandwidth;
        unsigned long dirty_ratelimit = wb->dirty_ratelimit;
@@ -1681,7 +1686,7 @@ void throttle_vm_writeout(gfp_t gfp_mask)
 
         for ( ; ; ) {
                global_dirty_limits(&background_thresh, &dirty_thresh);
-               dirty_thresh = hard_dirty_limit(dirty_thresh);
+               dirty_thresh = hard_dirty_limit(&global_wb_domain, dirty_thresh);
 
                 /*
                  * Boost the allowable dirty threshold a bit for page