mm: bdi: allow setting a maximum for the bdi dirty limit
Add "max_ratio" to /sys/class/bdi. This indicates the maximum percentage of
the global dirty threshold allocated to this bdi.
[mszeredi@suse.cz]
- fix parsing in max_ratio_store().
- export bdi_set_max_ratio() to modules
- limit bdi_dirty with bdi->max_ratio
- document new sysfs attribute
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4ac077f..2a9942f 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -164,7 +164,8 @@
*/
static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
{
- __prop_inc_percpu(&vm_completions, &bdi->completions);
+ __prop_inc_percpu_max(&vm_completions, &bdi->completions,
+ bdi->max_prop_frac);
}
static inline void task_dirty_inc(struct task_struct *tsk)
@@ -254,17 +255,43 @@
unsigned long flags;
spin_lock_irqsave(&bdi_lock, flags);
- min_ratio -= bdi->min_ratio;
- if (bdi_min_ratio + min_ratio < 100) {
- bdi_min_ratio += min_ratio;
- bdi->min_ratio += min_ratio;
- } else
+ if (min_ratio > bdi->max_ratio) {
ret = -EINVAL;
+ } else {
+ min_ratio -= bdi->min_ratio;
+ if (bdi_min_ratio + min_ratio < 100) {
+ bdi_min_ratio += min_ratio;
+ bdi->min_ratio += min_ratio;
+ } else {
+ ret = -EINVAL;
+ }
+ }
spin_unlock_irqrestore(&bdi_lock, flags);
return ret;
}
+int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ if (max_ratio > 100)
+ return -EINVAL;
+
+ spin_lock_irqsave(&bdi_lock, flags);
+ if (bdi->min_ratio > max_ratio) {
+ ret = -EINVAL;
+ } else {
+ bdi->max_ratio = max_ratio;
+ bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
+ }
+ spin_unlock_irqrestore(&bdi_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL(bdi_set_max_ratio);
+
/*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
@@ -365,6 +392,8 @@
bdi_dirty *= numerator;
do_div(bdi_dirty, denominator);
bdi_dirty += (dirty * bdi->min_ratio) / 100;
+ if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
+ bdi_dirty = dirty * bdi->max_ratio / 100;
*pbdi_dirty = bdi_dirty;
clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);