From c56e049a5e401a177c7c9b39a3bcc973ff5cec0b Mon Sep 17 00:00:00 2001
From: Stefan Roesch <shr@devkernel.io>
Date: Fri, 18 Nov 2022 16:52:03 -0800
Subject: [PATCH] mm: add knob /sys/class/bdi/<bdi>/max_bytes
This adds the new knob max_bytes to specify a dirty memory limit for the
corresponding bdi. The specified bytes value is converted to a ratio.
Link: https://lkml.kernel.org/r/20221119005215.3052436-9-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>
---
mm/backing-dev.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 90fa517123dc..95d3229fc81f 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 max_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_max_bytes(bdi));
+}
+
+static ssize_t max_bytes_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ u64 bytes;
+ ssize_t ret;
+
+ ret = kstrtoull(buf, 10, &bytes);
+ if (ret < 0)
+ return ret;
+
+ ret = bdi_set_max_bytes(bdi, bytes);
+ if (!ret)
+ ret = count;
+
+ return ret;
+}
+DEVICE_ATTR_RW(max_bytes);
+
static ssize_t stable_pages_required_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -241,6 +269,7 @@ 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_bytes.attr,
&dev_attr_stable_pages_required.attr,
&dev_attr_strict_limit.attr,
NULL,
--
2.30.9