Subject: + mm-add-strictlimit-knob-v2.patch added to -mm tree
To: MPatlasov@xxxxxxxxxxxxx,fengguang.wu@xxxxxxxxx,hmh@xxxxxxxxxx,jack@xxxxxxx,mel@xxxxxxxxx,t.artem@xxxxxxxxx,tytso@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 22 Nov 2013 15:47:49 -0800
The patch titled
Subject: mm: add strictlimit knob
has been added to the -mm tree. Its filename is
mm-add-strictlimit-knob-v2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-strictlimit-knob-v2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-strictlimit-knob-v2.patch
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From: Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx>
Subject: mm: add strictlimit knob
The "strictlimit" feature was introduced to enforce per-bdi dirty limits
for FUSE which sets bdi max_ratio to 1% by default:
http://article.gmane.org/gmane.linux.kernel.mm/105809
However the feature can be useful for other relatively slow or untrusted
BDIs like USB flash drives and DVD+RW. The patch adds a knob to enable
the feature:
echo 1 > /sys/class/bdi/X:Y/strictlimit
Being enabled, the feature enforces bdi max_ratio limit even if global
(10%) dirty limit is not reached. Of course, the effect is not visible
until /sys/class/bdi/X:Y/max_ratio is decreased to some reasonable value.
Signed-off-by: Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx>
Cc: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: "Artem S. Tashkinov" <t.artem@xxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-class-bdi | 8 ++++
mm/backing-dev.c | 35 ++++++++++++++++++++
2 files changed, 43 insertions(+)
diff -puN Documentation/ABI/testing/sysfs-class-bdi~mm-add-strictlimit-knob-v2 Documentation/ABI/testing/sysfs-class-bdi
--- a/Documentation/ABI/testing/sysfs-class-bdi~mm-add-strictlimit-knob-v2
+++ a/Documentation/ABI/testing/sysfs-class-bdi
@@ -53,3 +53,11 @@ stable_pages_required (read-only)
If set, the backing device requires that all pages comprising a write
request must not be changed until writeout is complete.
+
+strictlimit (read-write)
+
+ Forces per-BDI checks for the share of given device in the write-back
+ cache even before the global background dirty limit is reached. This
+ is useful in situations where the global limit is much higher than
+ affordable for given relatively slow (or untrusted) device. Turning
+ strictlimit on has no visible effect if max_ratio is equal to 100%.
diff -puN mm/backing-dev.c~mm-add-strictlimit-knob-v2 mm/backing-dev.c
--- a/mm/backing-dev.c~mm-add-strictlimit-knob-v2
+++ a/mm/backing-dev.c
@@ -234,11 +234,46 @@ static ssize_t stable_pages_required_sho
}
static DEVICE_ATTR_RO(stable_pages_required);
+static ssize_t strictlimit_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 val;
+ ssize_t ret;
+
+ ret = kstrtouint(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ switch (val) {
+ case 0:
+ bdi->capabilities &= ~BDI_CAP_STRICTLIMIT;
+ break;
+ case 1:
+ bdi->capabilities |= BDI_CAP_STRICTLIMIT;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return count;
+}
+static ssize_t strictlimit_show(struct device *dev,
+ struct device_attribute *attr, char *page)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+
+ return snprintf(page, PAGE_SIZE-1, "%d\n",
+ !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
+}
+static DEVICE_ATTR_RW(strictlimit);
+
static struct attribute *bdi_dev_attrs[] = {
&dev_attr_read_ahead_kb.attr,
&dev_attr_min_ratio.attr,
&dev_attr_max_ratio.attr,
&dev_attr_stable_pages_required.attr,
+ &dev_attr_strictlimit.attr,
NULL,
};
ATTRIBUTE_GROUPS(bdi_dev);
_
Patches currently in -mm which might be from MPatlasov@xxxxxxxxxxxxx are
origin.patch
mm-add-strictlimit-knob-v2.patch
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