From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f50.google.com (mail-pb0-f50.google.com [209.85.160.50]) by kanga.kvack.org (Postfix) with ESMTP id 606F16B0036 for ; Fri, 1 Nov 2013 10:31:52 -0400 (EDT) Received: by mail-pb0-f50.google.com with SMTP id uo5so4329358pbc.23 for ; Fri, 01 Nov 2013 07:31:52 -0700 (PDT) Received: from psmtp.com ([74.125.245.112]) by mx.google.com with SMTP id hj4si5018658pac.242.2013.11.01.07.31.48 for ; Fri, 01 Nov 2013 07:31:48 -0700 (PDT) Subject: [PATCH] mm: add strictlimit knob From: Maxim Patlasov Date: Fri, 01 Nov 2013 18:31:40 +0400 Message-ID: <20131101142941.1161.40314.stgit@dhcp-10-30-17-2.sw.ru> In-Reply-To: <20131031142612.GA28003@kipc2.localdomain> References: <20131031142612.GA28003@kipc2.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: karl.kiniger@med.ge.com Cc: jack@suse.cz, linux-kernel@vger.kernel.org, t.artem@lycos.com, linux-mm@kvack.org, mgorman@suse.de, tytso@mit.edu, akpm@linux-foundation.org, fengguang.wu@intel.com, torvalds@linux-foundation.org, mpatlasov@parallels.com "strictlimit" feature was introduced to enforce per-bdi dirty limits for FUSE which sets bdi max_ratio to 1% by default: http://www.http.com//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 max_ratio is decreased to some reasonable value. Signed-off-by: Maxim Patlasov --- mm/backing-dev.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index ce682f7..4ee1d64 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -234,11 +234,46 @@ static ssize_t stable_pages_required_show(struct device *dev, } 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); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org