bdi has two existing knobs to limit the amount of dirty memory:
min_ratio and max_ratio. However the granularity of the knobs is limited
and often it is more convenient to specify limits in terms of bytes.
This change adds the min_bytes knob.
It does not store the min_bytes value, instead it converts the max_bytes
value to a ratio. The value is therefore more an approximation than an
absolute value.
It also maintains the sum over all the bdi min_ratio values stored in
the variable bdi_min_ratio.
Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx>
---
mm/backing-dev.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index a3cad145b219..9962a2d92fe3 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -199,6 +199,34 @@ static ssize_t max_ratio_store(struct device *dev,
}
BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
+static ssize_t min_bytes_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+
+ return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
+}
+
+static ssize_t min_bytes_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ unsigned long long bytes;
+ ssize_t ret;
+
+ ret = kstrtoull(buf, 10, &bytes);
+ if (ret < 0)
+ return ret;
+
+ ret = bdi_set_min_bytes(bdi, bytes);
+ if (!ret)
+ ret = count;
+
+ return ret;
+}
+DEVICE_ATTR_RW(min_bytes);
+
static ssize_t max_bytes_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -269,6 +297,7 @@ static struct attribute *bdi_dev_attrs[] = {
&dev_attr_read_ahead_kb.attr,
&dev_attr_min_ratio.attr,
&dev_attr_max_ratio.attr,
+ &dev_attr_min_bytes.attr,
&dev_attr_max_bytes.attr,
&dev_attr_stable_pages_required.attr,
&dev_attr_strict_limit.attr,
--
2.30.2
