From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Schatzberg Subject: [PATCH v3 0/3] Charge loop device i/o to issuing cgroup Date: Thu, 20 Feb 2020 11:51:50 -0500 Message-ID: Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=6XRtdyMfa57xpaqGTGErpzosHOBJSLkhLdrjsJIgZOk=; b=GMVJvohK6Uqosdx++Q1UIJDcIwc443iVBHapmNkU3PGw0Gp/Zvb4sb4UC5bp2Vqnjh 3CNcPOyt+wKRKUoubWndo5lXBiYketttaeW/0TFZNT506r2ehW2MDLqDwKxIN4eTRL6l Bbe/9ss0aC0grEW3nn0C41VmK4UZ0iE4dj4Z897q8UHKgHY2T1n9bsgu9G2OYcIDvx+B u5klU2+Lw4xtVQXGaop6kWnEt+i2w3JLr/ZPKKBW51NDmVrAy3ZO3uQda80EIss6Qyv+ H/1orrfd8yQMyvriQ2xSQnzBmiCfFYpDXHVpOfkmdv3fLAt2kdPWJQVF2RC+gEgheTWP kuGQ== Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Cc: Dan Schatzberg , Jens Axboe , Tejun Heo , Li Zefan , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Hugh Dickins , Roman Gushchin , Shakeel Butt , Chris Down , Yang Shi , Thomas Gleixner , "open list:BLOCK LAYER" , open list , "open list:CONTROL GROUP CGROUP" , "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER MEMCG" Changes since V2: * Deferred destruction of workqueue items so in the common case there is no allocation needed Changes since V1: * Split out and reordered patches so cgroup charging changes are separate from kworker -> workqueue change * Add mem_css to struct loop_cmd to simplify logic The loop device runs all i/o to the backing file on a separate kworker thread which results in all i/o being charged to the root cgroup. This allows a loop device to be used to trivially bypass resource limits and other policy. This patch series fixes this gap in accounting. A simple script to demonstrate this behavior on cgroupv2 machine: ''' #!/bin/bash set -e CGROUP=/sys/fs/cgroup/test.slice LOOP_DEV=/dev/loop0 if [[ ! -d $CGROUP ]] then sudo mkdir $CGROUP fi grep oom_kill $CGROUP/memory.events # Set a memory limit, write more than that limit to tmpfs -> OOM kill sudo unshare -m bash -c " echo \$\$ > $CGROUP/cgroup.procs; echo 0 > $CGROUP/memory.swap.max; echo 64M > $CGROUP/memory.max; mount -t tmpfs -o size=512m tmpfs /tmp; dd if=/dev/zero of=/tmp/file bs=1M count=256" || true grep oom_kill $CGROUP/memory.events # Set a memory limit, write more than that limit through loopback # device -> no OOM kill sudo unshare -m bash -c " echo \$\$ > $CGROUP/cgroup.procs; echo 0 > $CGROUP/memory.swap.max; echo 64M > $CGROUP/memory.max; mount -t tmpfs -o size=512m tmpfs /tmp; truncate -s 512m /tmp/backing_file losetup $LOOP_DEV /tmp/backing_file dd if=/dev/zero of=$LOOP_DEV bs=1M count=256; losetup -D $LOOP_DEV" || true grep oom_kill $CGROUP/memory.events ''' Naively charging cgroups could result in priority inversions through the single kworker thread in the case where multiple cgroups are reading/writing to the same loop device. This patch series does some minor modification to the loop driver so that each cgroup can make forward progress independently to avoid this inversion. With this patch series applied, the above script triggers OOM kills when writing through the loop device as expected. Dan Schatzberg (3): loop: Use worker per cgroup instead of kworker mm: Charge active memcg when no mm is set loop: Charge i/o to mem and blk cg drivers/block/loop.c | 229 +++++++++++++++++++++++++++++++------ drivers/block/loop.h | 14 ++- include/linux/memcontrol.h | 6 + kernel/cgroup/cgroup.c | 1 + mm/memcontrol.c | 11 +- mm/shmem.c | 2 +- 6 files changed, 217 insertions(+), 46 deletions(-) -- 2.17.1