mm: add /sys/class/bdi/<bdi>/max_ratio_fine knob

This adds the max_ratio_fine knob. The knob specifies the values not
based on 1 of 100, but instead 1 per million.

Link: https://lkml.kernel.org/r/20221119005215.3052436-17-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 3fab790..94c2382 100644 (file)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -199,6 +199,25 @@ static ssize_t max_ratio_store(struct device *dev,
 }
 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
 
+static ssize_t max_ratio_fine_store(struct device *dev,
+               struct device_attribute *attr, const char *buf, size_t count)
+{
+       struct backing_dev_info *bdi = dev_get_drvdata(dev);
+       unsigned int ratio;
+       ssize_t ret;
+
+       ret = kstrtouint(buf, 10, &ratio);
+       if (ret < 0)
+               return ret;
+
+       ret = bdi_set_max_ratio_no_scale(bdi, ratio);
+       if (!ret)
+               ret = count;
+
+       return ret;
+}
+BDI_SHOW(max_ratio_fine, bdi->max_ratio)
+
 static ssize_t min_bytes_show(struct device *dev,
                              struct device_attribute *attr,
                              char *buf)
@@ -297,6 +316,7 @@ static struct attribute *bdi_dev_attrs[] = {
        &dev_attr_read_ahead_kb.attr,
        &dev_attr_min_ratio.attr,
        &dev_attr_max_ratio.attr,
+       &dev_attr_max_ratio_fine.attr,
        &dev_attr_min_bytes.attr,
        &dev_attr_max_bytes.attr,
        &dev_attr_stable_pages_required.attr,