writeback: move global_dirty_limit into wb_domain

[cascardo/linux.git] / include / linux / writeback.h

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 3148db1..5fdd4e1 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -95,6 +95,8 @@ struct writeback_control {
  * dirtyable memory accordingly.
  */
 struct wb_domain {
+       spinlock_t lock;
+
        /*
         * Scale the writeback cache size proportional to the relative
         * writeout speed.
@@ -115,6 +117,19 @@ struct wb_domain {
        struct fprop_global completions;
        struct timer_list period_timer; /* timer for aging of completions */
        unsigned long period_time;
+
+       /*
+        * The dirtyable memory and dirty threshold could be suddenly
+        * knocked down by a large amount (eg. on the startup of KVM in a
+        * swapless system). This may throw the system into deep dirty
+        * exceeded state and throttle heavy/light dirtiers alike. To
+        * retain good responsiveness, maintain global_dirty_limit for
+        * tracking slowly down to the knocked down dirty threshold.
+        *
+        * Both fields are protected by ->lock.
+        */
+       unsigned long dirty_limit_tstamp;
+       unsigned long dirty_limit;
 };
 
 /*
@@ -153,7 +168,7 @@ void throttle_vm_writeout(gfp_t gfp_mask);
 bool zone_dirty_ok(struct zone *zone);
 int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
 
-extern unsigned long global_dirty_limit;
+extern struct wb_domain global_wb_domain;
 
 /* These are exported to sysctl. */
 extern int dirty_background_ratio;