From: Stefan Roesch shr@devkernel.io
mainline inclusion from mainline-v6.2-rc1 commit 9c84819bd64ec15cb15d041c45ebe4725e9d4f3b category: feature bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAN96I
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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.
Link: https://lkml.kernel.org/r/20221119005215.3052436-14-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 Signed-off-by: Yifan Qiao qiaoyifan4@huawei.com --- mm/backing-dev.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 383bf0a8f90e..b3595a3b06b2 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -197,6 +197,34 @@ 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); + u64 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) @@ -267,6 +295,7 @@ 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,