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Date:   Thu, 21 May 2020 17:47:05 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Chris Down <chris@...isdown.name>,
        Michal Hocko <mhocko@...nel.org>,
        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, May 21, 2020 at 4:59 PM Naresh Kamboju
<naresh.kamboju@...aro.org> wrote:
>
> On Thu, 21 May 2020 at 08:10, Yafang Shao <laoar.shao@...il.com> wrote:
> >
> > On Thu, May 21, 2020 at 2:00 AM Naresh Kamboju
> > <naresh.kamboju@...aro.org> wrote:
> > >
> > > On Wed, 20 May 2020 at 17:26, Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
> > > >
> > > >
> > > > This issue is specific on 32-bit architectures i386 and arm on linux-next tree.
> > > > As per the test results history this problem started happening from
> > > > mkfs -t ext4 /dev/disk/by-id/ata-SanDisk_SSD_PLUS_120GB_190804A00BE5
> > > >
> > > >
> > > > Problem:
> > > > [   38.802375] dd invoked oom-killer: gfp_mask=0x100cc0(GFP_USER),
> > > > order=0, oom_score_adj=0
> > >
> > My guess is that we made the same mistake in commit "mm, memcg:
> > decouple e{low,min} state mutations from protection
> > checks" that it read a stale memcg protection in
> > mem_cgroup_below_low() and mem_cgroup_below_min().
> >
> > Bellow is a possble fix,
>
> Sorry. The proposed fix did not work.
> I have took your patch and applied on top of linux-next master branch and
> tested and mkfs -t ext4 invoked oom-killer.
>
> After patch applied test log link,
> https://lkft.validation.linaro.org/scheduler/job/1443936#L1168
>
>
> test  log,
> + 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: ab107250-bf18-4357-a06a-67f2bfcc1048
> 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): [   34.423940] mkfs.ext4 invoked
> oom-killer: gfp_mask=0x101cc0(GFP_USER|__GFP_WRITE), order=0,
> oom_score_adj=0
> [   34.433694] CPU: 0 PID: 402 Comm: mkfs.ext4 Not tainted
> 5.7.0-rc6-next-20200519+ #1
> [   34.441342] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS
> 2.2 05/23/2018
> [   34.448734] Call Trace:
> [   34.451196]  dump_stack+0x54/0x76
> [   34.454517]  dump_header+0x40/0x1f0
> [   34.458008]  ? oom_badness+0x1f/0x120
> [   34.461673]  ? ___ratelimit+0x6c/0xe0
> [   34.465332]  oom_kill_process+0xc9/0x110
> [   34.469255]  out_of_memory+0xd7/0x2f0
> [   34.472916]  __alloc_pages_nodemask+0xdd1/0xe90
> [   34.477446]  ? set_bh_page+0x33/0x50
> [   34.481016]  ? __xa_set_mark+0x4d/0x70
> [   34.484762]  pagecache_get_page+0xbe/0x250
> [   34.488859]  grab_cache_page_write_begin+0x1a/0x30
> [   34.493645]  block_write_begin+0x25/0x90
> [   34.497569]  blkdev_write_begin+0x1e/0x20
> [   34.501574]  ? bdev_evict_inode+0xc0/0xc0
> [   34.505578]  generic_perform_write+0x95/0x190
> [   34.509927]  __generic_file_write_iter+0xe0/0x1a0
> [   34.514626]  blkdev_write_iter+0xbf/0x1c0
> [   34.518630]  __vfs_write+0x122/0x1e0
> [   34.522200]  vfs_write+0x8f/0x1b0
> [   34.525510]  ksys_pwrite64+0x60/0x80
> [   34.529081]  __ia32_sys_ia32_pwrite64+0x16/0x20
> [   34.533604]  do_fast_syscall_32+0x66/0x240
> [   34.537697]  entry_SYSENTER_32+0xa5/0xf8
> [   34.541613] EIP: 0xb7f3c549
> [   34.544403] Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01
> 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f
> 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90
> 8d 76
> [   34.563140] EAX: ffffffda EBX: 00000003 ECX: b7830010 EDX: 00400000
> [   34.569397] ESI: 38400000 EDI: 00000074 EBP: 07438400 ESP: bff1e650
> [   34.575654] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000246
> [   34.582453] Mem-Info:
> [   34.584732] active_anon:5713 inactive_anon:2169 isolated_anon:0
> [   34.584732]  active_file:4040 inactive_file:211204 isolated_file:0
> [   34.584732]  unevictable:0 dirty:17270 writeback:6240 unstable:0
> [   34.584732]  slab_reclaimable:5856 slab_unreclaimable:3439
> [   34.584732]  mapped:6192 shmem:2258 pagetables:178 bounce:0
> [   34.584732]  free:265105 free_pcp:1330 free_cma:0
> [   34.618483] Node 0 active_anon:22852kB inactive_anon:8676kB
> active_file:16160kB inactive_file:844816kB unevictable:0kB
> isolated(anon):0kB isolated(file):0kB mapped:24768kB dirty:69080kB
> writeback:19628kB shmem:9032kB writeback_tmp:0kB unstable:0kB
> all_unreclaimable? yes
> [   34.642354] DMA free:3588kB min:68kB low:84kB high:100kB
> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
> active_file:0kB inactive_file:11848kB unevictable:0kB
> writepending:11856kB present:15964kB managed:15876kB mlocked:0kB
> kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB
> free_cma:0kB
> [   34.670194] lowmem_reserve[]: 0 824 1947 824
> [   34.674483] Normal free:4228kB min:3636kB low:4544kB high:5452kB
> reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB
> active_file:1136kB inactive_file:786456kB unevictable:0kB
> writepending:68084kB present:884728kB managed:845324kB mlocked:0kB
> kernel_stack:1104kB pagetables:0kB bounce:0kB free_pcp:3056kB
> local_pcp:388kB free_cma:0kB
> [   34.704243] lowmem_reserve[]: 0 0 8980 0
> [   34.708189] HighMem free:1053028kB min:512kB low:1748kB high:2984kB
> reserved_highatomic:0KB active_anon:22852kB inactive_anon:8676kB
> active_file:15024kB inactive_file:46596kB unevictable:0kB
> writepending:0kB present:1149544kB managed:1149544kB mlocked:0kB
> kernel_stack:0kB pagetables:712kB bounce:0kB free_pcp:2160kB
> local_pcp:736kB free_cma:0kB
> [   34.738563] lowmem_reserve[]: 0 0 0 0
> [   34.742245] DMA: 23*4kB (U) 2*8kB (U) 3*16kB (U) 2*32kB (UE) 2*64kB
> (U) 1*128kB (U) 1*256kB (E) 0*512kB 1*1024kB (E) 1*2048kB (E) 0*4096kB
> = 3804kB
> [   34.755479] Normal: 25*4kB (UM) 27*8kB (UME) 16*16kB (UME) 14*32kB
> (UME) 7*64kB (UME) 2*128kB (UM) 1*256kB (E) 1*512kB (E) 0*1024kB
> 1*2048kB (M) 0*4096kB = 4540kB
> [   34.770004] HighMem: 1*4kB (U) 0*8kB 0*16kB 1*32kB (U) 1*64kB (M)
> 2*128kB (UM) 2*256kB (UM) 1*512kB (U) 1*1024kB (U) 1*2048kB (U)
> 256*4096kB (M) = 1053028kB
> [   34.784010] Node 0 hugepages_total=0 hugepages_free=0
> hugepages_surp=0 hugepages_size=4096kB
> [   34.792466] 217507 total pagecache pages
> [   34.796387] 0 pages in swap cache
> [   34.799704] Swap cache stats: add 0, delete 0, find 0/0
> [   34.804923] Free swap  = 0kB
> [   34.807834] Total swap = 0kB
> [   34.810738] 512559 pages RAM
> [   34.813640] 287386 pages HighMem/MovableOnly
> [   34.817931] 9873 pages reserved
>
>
> - Naresh


Thanks for your work.
I just noticed that this is a system oom, rather than a memcg oom.
While this patch is against memcg oom.

As you have verified this oom is only caused by commit "mm, memcg:
decouple e{low,min} state mutations from protection checks",
this commit really introduce the issue of using the stale protection
value, but I haven't thought deeply why this occurs. This issue can
occur only  when you set memcg {min, low} protection, but
unfortunately memcg {min, low} isn't shown in the oom log.

Appreciat if you would like to check the memcg {min, low} protection
setting. If they are set, I think bellow workaround can avoid this
issue.

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 474815a..f6f794a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6380,6 +6380,9 @@ void mem_cgroup_calculate_protection(struct
mem_cgroup *root,
        if (mem_cgroup_disabled())
                return;

+       memcg->memory.elow = 0;
+       memcg->memory.emin = 0;
+
        if (!root)
                root = root_mem_cgroup;

But I think the right thing to do now is reverting the bad commit,
because the usage of memory.{emin, elow} is very subtle, we shouldn't
place them here and there at the risk of reading a stale value.

-- 
Thanks
Yafang

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