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Message-ID: <CACfi_Z0WeUL=RhPbEjwRBnVgr_DAQCbqgpfX-fif+A_XrhAspA@mail.gmail.com>
Date: Mon, 25 May 2020 23:22:30 -0400
From: Davis Roman <davis.roman84@...il.com>
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu, adilger.kernel@...ger.ca
Subject: trying to make sense out of kernel oops generated in ext4 subsystem
while kernel was experiencing high memory pressure
Hello,
I got a kernel oops from what appears to be ext4 while my system was
very low on memory. I compiled my kernel with debug symbols and traced
it down to a BUG_ON statement in fs/ext4/inode.c but I'm having a
hard time trying to figure it out from there.
Any help or insights would be appreciated,
Thank you,
Davis
internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP ARM
Modules linked in: cdc_mbim cdc_wdm cdc_ncm usbnet mii cdc_acm
xt_multiport nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter
ip6_tables iptable_nat nf_nat_ipv4 ipt_MASQUERADE
nf_nat_masquerade_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
xt_state iptable_filter xt_conntrack nf_conntrack libcrc32c ip_tables
m25p80 gc2145_camera imx_sdma virt_dma ath9k ath9k_common ath9k_hw ath
g_ether usb_f_rndis u_ether libcomposite cryptodev(O) [last unloaded:
at25]
CPU: 0 PID: 33 Comm: kswapd0 Tainted: 4.14.154 #1
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
task: 8812d140 task.stack: 88af4000
PC is at ext4_writepage+0x564/0x774
LR is at shrink_page_list+0x7e4/0xde0
pc : [<802d7f6c>] lr : [<801fea9c>] psr: 000e0013
sp : 88af5ce0 ip : 00000000 fp : 88af5d98
r10: 88af5da8 r9 : 865f2978 r8 : 865f2a54
r7 : 00000000 r6 : 9fedebe0 r5 : 00000001 r4 : 00001000
r3 : 00000000 r2 : 00000125 r1 : 00000000 r0 : 000000ea
Flags: nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
Control: 10c53c7d Table: 147f4059 DAC: 00000051
Process kswapd0 (pid: 33, stack limit = 0x88af4210)
Stack: (0x88af5ce0 to 0x88af6000)
5ce0: 86425750 00064ea6 8642574c 801ec094 88e2c268 88e2c268 88e2c200 ffffffff
5d00: 88af5d98 8042ad38 9fedebe0 88e2c200 00000000 80f03d88 865f2a54 9fedebf4
5d20: 9fedebe0 00000000 88af5f34 865f2a54 00000000 88af5e14 88af5d98 801fea9c
5d40: 00000001 00000003 00000000 00000006 00000000 00000003 88af4000 00000000
5d60: 00000000 0000000f 80f821c0 00000000 00000000 88af5e1c 80fe9f8c 00000000
5d80: 00000000 80e59d74 88af5d40 00000001 00000003 0001ddac 9ff0e574 9ff14ff4
5da0: 9ff08234 9ff0e554 00000020 00000000 00000000 00000000 ffffffff 7fffffff
5dc0: 00000000 00000008 00000000 80f03d88 80e5dccd 80f82e44 88af5f34 00000008
5de0: 00000020 80f82e40 00000000 80f821c0 00000002 801ff7e0 88af5e1c 00000000
5e00: 00000002 80f821c0 00000000 80f821c4 00000020 9ff082d4 9fc41c74 00000000
5e20: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 80f03d88
5e40: 0000173d 00000002 00000152 00000037 88af5ec4 00000020 00000000 80f82e44
5e60: 88af5f34 80200178 88af5ecc 80f821c0 80f03ac0 0000171e 00000000 00000265
5e80: ffffffff ffffffff 51eb851f 80f82e44 000000ee 00000000 88af5f30 88af4000
5ea0: 00000001 88af5ea4 88af5ea4 88af5eac 88af5eac 88af5eb4 88af5eb4 00000000
5ec0: 00000000 00000152 00000295 0000027b 00000000 00000000 00000252 00000375
5ee0: 0000027b 80f03d88 00000000 00000000 00000000 000000ee 00000001 80f82e44
5f00: 00000000 80f821c0 80feb5a0 80200f78 80fe1d40 88af4000 88af5f10 80167694
5f20: ffffe000 80e59da0 80e59d9c 8812d140 00000000 00000265 014000c0 00000000
5f40: 00000000 00000000 00000002 00000000 00000007 000001b8 000000ee 80f03d88
5f60: ffffe000 88282e00 88282d40 00000000 88af4000 80f821c0 80200c54 88282e1c
5f80: 8803de74 8014da78 88af4000 88282d40 8014d954 00000000 00000000 00000000
5fa0: 00000000 00000000 00000000 80108928 00000000 00000000 00000000 00000000
5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[<802d7f6c>] (ext4_writepage) from [<801fea9c>] (shrink_page_list+0x7e4/0xde0)
[<801fea9c>] (shrink_page_list) from [<801ff7e0>]
(shrink_inactive_list+0x1c4/0x3dc)
[<801ff7e0>] (shrink_inactive_list) from [<80200178>] (shrink_node+0x44c/0x8b0)
[<80200178>] (shrink_node) from [<80200f78>] (kswapd+0x324/0x668)
[<80200f78>] (kswapd) from [<8014da78>] (kthread+0x124/0x154)
[<8014da78>] (kthread) from [<80108928>] (ret_from_fork+0x14/0x2c)
Code: e519305c e3130b02 0afffefc eaffffc6 (e7f001f2)
---[ end trace 74cf38da7549a08d ]---
Kernel panic - not syncing: Fatal exception
$ arm-poky-linux-gnueabi-addr2line -fe vmlinux 802d7f6c
__ext4_journalled_writepage
/home/davis/linux-rezi/fs/ext4/inode.c:2026
$ bat -r 2019:2029 /home/davis/linux-rezi/fs/ext4/inode.c
2019 │ handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
2020 │ ext4_writepage_trans_blocks(inode));
2021 │ if (IS_ERR(handle)) {
2022 │ ret = PTR_ERR(handle);
2023 │ put_page(page);
2024 │ goto out_no_pagelock;
2025 │ }
2026 │ BUG_ON(!ext4_handle_valid(handle)); <~~~
2027 │
2028 │ lock_page(page);
2029 │ put_page(page);
davis@...cision-7920:~/linux-rezi$ ./scripts/decodecode < /tmp/oops.txt
Code: e519305c e3130b02 0afffefc eaffffc6 (e7f001f2)
All code
========
0: 5c pop %rsp
1: 30 19 xor %bl,(%rcx)
3: e5 02 in $0x2,%eax
5: 0b 13 or (%rbx),%edx
7: e3 fc jrcxz 0x5
9: fe (bad)
a: ff 0a decl (%rdx)
c: c6 (bad)
d: ff (bad)
e: ff (bad)
f: ea (bad)
10:* f2 01 f0 repnz add %esi,%eax <-- trapping instruction
13: e7 .byte 0xe7
Code starting with the faulting instruction
===========================================
0: f2 01 f0 repnz add %esi,%eax
3: e7 .byte 0xe7
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