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Date: Thu, 21 May 2020 05:24:27 -0700 (PDT) From: Hugh Dickins <hughd@...gle.com> To: Michal Hocko <mhocko@...nel.org> cc: Naresh Kamboju <naresh.kamboju@...aro.org>, Chris Down <chris@...isdown.name>, Yafang Shao <laoar.shao@...il.com>, Anders Roxell <anders.roxell@...aro.org>, "Linux F2FS DEV, Mailing List" <linux-f2fs-devel@...ts.sourceforge.net>, linux-ext4 <linux-ext4@...r.kernel.org>, linux-block <linux-block@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, open list <linux-kernel@...r.kernel.org>, Linux-Next Mailing List <linux-next@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Arnd Bergmann <arnd@...db.de>, Andreas Dilger <adilger.kernel@...ger.ca>, Jaegeuk Kim <jaegeuk@...nel.org>, Theodore Ts'o <tytso@....edu>, Chao Yu <chao@...nel.org>, Hugh Dickins <hughd@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Matthew Wilcox <willy@...radead.org>, Chao Yu <yuchao0@...wei.com>, lkft-triage@...ts.linaro.org, Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>, Cgroups <cgroups@...r.kernel.org> Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page 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 <mhocko@...nel.org> 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. --- 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,
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