From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:59058 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753220AbdCHNOt (ORCPT ); Wed, 8 Mar 2017 08:14:49 -0500 Subject: Patch "mm: vmpressure: fix sending wrong events on underflow" has been added to the 4.4-stable tree To: vinmenon@codeaurora.org, akpm@linux-foundation.org, anton.vorontsov@linaro.org, gregkh@linuxfoundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, mhocko@suse.com, minchan@kernel.org, riel@redhat.com, shashim@codeaurora.org, torvalds@linux-foundation.org, vbabka@suse.cz, vdavydov.dev@gmail.com Cc: , From: Date: Wed, 08 Mar 2017 14:12:53 +0100 Message-ID: <148897877323041@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm: vmpressure: fix sending wrong events on underflow to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-vmpressure-fix-sending-wrong-events-on-underflow.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From e1587a4945408faa58d0485002c110eb2454740c Mon Sep 17 00:00:00 2001 From: Vinayak Menon Date: Fri, 24 Feb 2017 14:59:39 -0800 Subject: mm: vmpressure: fix sending wrong events on underflow From: Vinayak Menon commit e1587a4945408faa58d0485002c110eb2454740c upstream. At the end of a window period, if the reclaimed pages is greater than scanned, an unsigned underflow can result in a huge pressure value and thus a critical event. Reclaimed pages is found to go higher than scanned because of the addition of reclaimed slab pages to reclaimed in shrink_node without a corresponding increment to scanned pages. Minchan Kim mentioned that this can also happen in the case of a THP page where the scanned is 1 and reclaimed could be 512. Link: http://lkml.kernel.org/r/1486641577-11685-1-git-send-email-vinmenon@codeaurora.org Signed-off-by: Vinayak Menon Acked-by: Minchan Kim Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Mel Gorman Cc: Vlastimil Babka Cc: Rik van Riel Cc: Vladimir Davydov Cc: Anton Vorontsov Cc: Shiraz Hashim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/vmpressure.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/mm/vmpressure.c +++ b/mm/vmpressure.c @@ -112,9 +112,16 @@ static enum vmpressure_levels vmpressure unsigned long reclaimed) { unsigned long scale = scanned + reclaimed; - unsigned long pressure; + unsigned long pressure = 0; /* + * reclaimed can be greater than scanned in cases + * like THP, where the scanned is 1 and reclaimed + * could be 512 + */ + if (reclaimed >= scanned) + goto out; + /* * We calculate the ratio (in percents) of how many pages were * scanned vs. reclaimed in a given time frame (window). Note that * time is in VM reclaimer's "ticks", i.e. number of pages @@ -124,6 +131,7 @@ static enum vmpressure_levels vmpressure pressure = scale - (reclaimed * scale / scanned); pressure = pressure * 100 / scale; +out: pr_debug("%s: %3lu (s: %lu r: %lu)\n", __func__, pressure, scanned, reclaimed); Patches currently in stable-queue which might be from vinmenon@codeaurora.org are queue-4.4/mm-vmpressure-fix-sending-wrong-events-on-underflow.patch