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[37.188.180.112]) by smtp.gmail.com with ESMTPSA id rn17sm4757851ejb.115.2020.05.21.05.44.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 May 2020 05:44:45 -0700 (PDT) Date: Thu, 21 May 2020 14:44:44 +0200 From: Michal Hocko To: Hugh Dickins Cc: Naresh Kamboju , Chris Down , Yafang Shao , Anders Roxell , "Linux F2FS DEV, Mailing List" , linux-ext4 , linux-block , Andrew Morton , open list , Linux-Next Mailing List , linux-mm , Arnd Bergmann , Andreas Dilger , Jaegeuk Kim , Theodore Ts'o , Chao Yu , Andrea Arcangeli , Matthew Wilcox , Chao Yu , lkft-triage@lists.linaro.org, Johannes Weiner , Roman Gushchin , Cgroups Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page Message-ID: <20200521124444.GP6462@dhcp22.suse.cz> References: <20200519075213.GF32497@dhcp22.suse.cz> <20200519084535.GG32497@dhcp22.suse.cz> <20200520190906.GA558281@chrisdown.name> <20200521095515.GK6462@dhcp22.suse.cz> <20200521105801.GL6462@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 21-05-20 05:24:27, Hugh Dickins wrote: > On Thu, 21 May 2020, Michal Hocko wrote: > > On Thu 21-05-20 16:11:11, Naresh Kamboju wrote: > > > On Thu, 21 May 2020 at 15:25, Michal Hocko wrote: > > > > > > > > On Wed 20-05-20 20:09:06, Chris Down wrote: > > > > > Hi Naresh, > > > > > > > > > > Naresh Kamboju writes: > > > > > > As a part of investigation on this issue LKFT teammate Anders Roxell > > > > > > git bisected the problem and found bad commit(s) which caused this problem. > > > > > > > > > > > > The following two patches have been reverted on next-20200519 and retested the > > > > > > reproducible steps and confirmed the test case mkfs -t ext4 got PASS. > > > > > > ( invoked oom-killer is gone now) > > > > > > > > > > > > Revert "mm, memcg: avoid stale protection values when cgroup is above > > > > > > protection" > > > > > > This reverts commit 23a53e1c02006120f89383270d46cbd040a70bc6. > > > > > > > > > > > > Revert "mm, memcg: decouple e{low,min} state mutations from protection > > > > > > checks" > > > > > > This reverts commit 7b88906ab7399b58bb088c28befe50bcce076d82. > > > > > > > > > > Thanks Anders and Naresh for tracking this down and reverting. > > > > > > > > > > I'll take a look tomorrow. I don't see anything immediately obviously wrong > > > > > in either of those commits from a (very) cursory glance, but they should > > > > > only be taking effect if protections are set. > > > > > > > > Agreed. If memory.{low,min} is not used then the patch should be > > > > effectively a nop. Btw. do you see the problem when booting with > > > > cgroup_disable=memory kernel command line parameter? > > > > > > With extra kernel command line parameters, cgroup_disable=memory > > > I have noticed a differ problem now. > > > > > > + mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8NRK0BPF6XF > > > mke2fs 1.43.8 (1-Jan-2018) > > > Creating filesystem with 244190646 4k blocks and 61054976 inodes > > > Filesystem UUID: 3bb1a285-2cb4-44b4-b6e8-62548f3ac620 > > > Superblock backups stored on blocks: > > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, > > > 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, > > > 102400000, 214990848 > > > Allocating group tables: 0/7453 done > > > Writing inode tables: 0/7453 done > > > Creating journal (262144 blocks): [ 35.502102] BUG: kernel NULL > > > pointer dereference, address: 000000c8 > > > [ 35.508372] #PF: supervisor read access in kernel mode > > > [ 35.513506] #PF: error_code(0x0000) - not-present page > > > [ 35.518638] *pde = 00000000 > > > [ 35.521514] Oops: 0000 [#1] SMP > > > [ 35.524652] CPU: 0 PID: 145 Comm: kswapd0 Not tainted > > > 5.7.0-rc6-next-20200519+ #1 > > > [ 35.532121] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS > > > 2.2 05/23/2018 > > > [ 35.539507] EIP: mem_cgroup_get_nr_swap_pages+0x28/0x60 > > > > Could you get faddr2line for this offset? > > No need for that, I can help with the "cgroup_disabled=memory" crash: > I've been happily running with the fixup below, but haven't got to > send it in yet (and wouldn't normally be reading mail at this time!) > because of busy chasing a couple of other bugs (not necessarily mm); > and maybe the fix would be better with explicit mem_cgroup_disabled() > test, or maybe that should be where cgroup_memory_noswap is decided - > up to Johannes. Thanks Hugh. I can see what is the problem now. I was looking at the Linus' tree and we have a different code there long nr_swap_pages = get_nr_swap_pages(); if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) return nr_swap_pages; which would be impossible to crash so I was really wondering what is going on here. But there are other changes in the mmotm which I haven't reviewed yet. Looking at the next tree now it is a fallout from "mm: memcontrol: prepare swap controller setup for integration". !memcg check slightly more cryptic than an explicit mem_cgroup_disabled but I would just leave it to Johannes as well. > > --- > > mm/memcontrol.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > --- 5.7-rc6-mm1/mm/memcontrol.c 2020-05-20 12:21:56.109693740 -0700 > +++ linux/mm/memcontrol.c 2020-05-20 12:26:15.500478753 -0700 > @@ -6954,7 +6954,8 @@ long mem_cgroup_get_nr_swap_pages(struct > { > long nr_swap_pages = get_nr_swap_pages(); > > - if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + if (!memcg || cgroup_memory_noswap || > + !cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return nr_swap_pages; > for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) > nr_swap_pages = min_t(long, nr_swap_pages, -- Michal Hocko SUSE Labs