* INFO: task hung in mpage_prepare_extent_to_map
@ 2019-10-28 19:52 syzbot
2019-10-28 20:14 ` Johannes Weiner
0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2019-10-28 19:52 UTC (permalink / raw)
To: akpm, amir73il, darrick.wong, hannes, hughd, jack, jglisse,
josef, kirill.shutemov, linux-kernel, linux-mm, sfr,
songliubraving, syzkaller-bugs, william.kucharski, willy
Hello,
syzbot found the following crash on:
HEAD commit: 12d61c69 Add linux-next specific files for 20191024
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15a0fa97600000
kernel config: https://syzkaller.appspot.com/x/.config?x=afb75fd8c9fd5ed8
dashboard link: https://syzkaller.appspot.com/bug?extid=efb9e48b9fbdc49bb34a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13a63dc4e00000
The bug was bisected to:
commit 9c61acffe2b8833152041f7b6a02d1d0a17fd378
Author: Song Liu <songliubraving@fb.com>
Date: Wed Oct 23 00:24:28 2019 +0000
mm,thp: recheck each page before collapsing file THP
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13eb6ec0e00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=101b6ec0e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=17eb6ec0e00000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+efb9e48b9fbdc49bb34a@syzkaller.appspotmail.com
Fixes: 9c61acffe2b8 ("mm,thp: recheck each page before collapsing file THP")
INFO: task khugepaged:1084 blocked for more than 143 seconds.
Not tainted 5.4.0-rc4-next-20191024 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
khugepaged D27568 1084 2 0x80004000
Call Trace:
context_switch kernel/sched/core.c:3384 [inline]
__schedule+0x94a/0x1e70 kernel/sched/core.c:4069
schedule+0xd9/0x260 kernel/sched/core.c:4136
io_schedule+0x1c/0x70 kernel/sched/core.c:5780
wait_on_page_bit_common mm/filemap.c:1175 [inline]
__lock_page+0x422/0xab0 mm/filemap.c:1383
lock_page include/linux/pagemap.h:480 [inline]
mpage_prepare_extent_to_map+0xb3f/0xf90 fs/ext4/inode.c:2668
ext4_writepages+0xb6a/0x2e70 fs/ext4/inode.c:2866
? 0xffffffff81000000
do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
__filemap_fdatawrite_range+0x2bc/0x3b0 mm/filemap.c:421
__filemap_fdatawrite mm/filemap.c:429 [inline]
filemap_flush+0x24/0x30 mm/filemap.c:456
collapse_file+0x36b1/0x41a0 mm/khugepaged.c:1652
khugepaged_scan_file mm/khugepaged.c:1890 [inline]
khugepaged_scan_mm_slot mm/khugepaged.c:1988 [inline]
khugepaged_do_scan mm/khugepaged.c:2072 [inline]
khugepaged+0x2da9/0x4360 mm/khugepaged.c:2117
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Showing all locks held in the system:
4 locks held by kworker/u4:0/7:
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at:
__write_once_size include/linux/compiler.h:226 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:855 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:40 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at: set_work_data
kernel/workqueue.c:620 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
#0: ffff8880a8284d28 ((wq_completion)writeback){+.+.}, at:
process_one_work+0x88b/0x1740 kernel/workqueue.c:2240
#1: ffff8880a988fdc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}, at:
process_one_work+0x8c1/0x1740 kernel/workqueue.c:2244
#2: ffff88809b03a0d8 (&type->s_umount_key#32){++++}, at:
trylock_super+0x22/0x110 fs/super.c:418
#3: ffff88809b03c990 (&sbi->s_journal_flag_rwsem){.+.+}, at:
do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
1 lock held by khungtaskd/1077:
#0: ffffffff88faba80 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5336
1 lock held by khugepaged/1084:
#0: ffff88809b03c990 (&sbi->s_journal_flag_rwsem){.+.+}, at:
do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
1 lock held by rsyslogd/8623:
#0: ffff888098f5d860 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:801
2 locks held by getty/8713:
#0: ffff8880a1ca4090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f392e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8714:
#0: ffff8880a0faf090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f352e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8715:
#0: ffff8880a0b1e090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f192e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8716:
#0: ffff8880a9486090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f112e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8717:
#0: ffff8880a161a090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f312e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8718:
#0: ffff888095db3090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f212e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/8719:
#0: ffff88809b09e090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc90005f092e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
1 lock held by syz-execprog/8740:
#0: ffff8880a657d3e8 (&ei->i_mmap_sem){++++}, at:
ext4_filemap_fault+0x7e/0xb2 fs/ext4/inode.c:6291
=============================================
NMI backtrace for cpu 1
CPU: 1 PID: 1077 Comm: khungtaskd Not tainted 5.4.0-rc4-next-20191024 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:269 [inline]
watchdog+0xc8f/0x1350 kernel/hung_task.c:353
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc4-next-20191024 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:update_group_capacity+0xa/0x920 kernel/sched/fair.c:7647
Code: e8 0b 84 5b 00 e9 57 fd ff ff 48 8b 7d c8 e8 1d 84 5b 00 e9 49 fe ff
ff 0f 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df <55> 48 89 e5 41
57 41 56 49 89 fe 48 83 c7 08 48 89 fa 41 55 48 c1
RSP: 0018:ffff8880ae809878 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffff8880ae809a50 RCX: ffffffff8153db8d
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880a9813000
RBP: ffff8880ae809b20 R08: 1ffff110153038a4 R09: ffffed10153038a5
R10: ffffed10153038a4 R11: ffff8880a981c527 R12: dffffc0000000000
R13: ffff8880a981c520 R14: ffff8880ae809af8 R15: ffff8880ae809c30
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c420000240 CR3: 00000000a5df3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
load_balance+0x389/0x2a90 kernel/sched/fair.c:8987
rebalance_domains+0x66a/0xba0 kernel/sched/fair.c:9413
_nohz_idle_balance+0x336/0x3f0 kernel/sched/fair.c:9826
nohz_idle_balance kernel/sched/fair.c:9872 [inline]
run_rebalance_domains+0x1c6/0x2d0 kernel/sched/fair.c:10056
__do_softirq+0x262/0x98c kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x19b/0x1e0 kernel/softirq.c:413
scheduler_ipi+0x38c/0x610 kernel/sched/core.c:2347
smp_reschedule_interrupt+0x78/0x4c0 arch/x86/kernel/smp.c:244
reschedule_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:853
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: a8 95 5a fa eb 8a 90 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 84 a7 53
00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 74 a7 53 00 fb f4 <c3> 90 55 48 89
e5 41 57 41 56 41 55 41 54 53 e8 be 75 0c fa e8 79
RSP: 0018:ffffffff88e07ce8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02
RAX: 1ffffffff11e643f RBX: ffffffff88e7a1c0 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffffffff88e7aa5c
RBP: ffffffff88e07d18 R08: ffffffff88e7a1c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffffff89c81680 R14: 0000000000000000 R15: 0000000000000000
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571
default_idle_call+0x84/0xb0 kernel/sched/idle.c:94
cpuidle_idle_call kernel/sched/idle.c:154 [inline]
do_idle+0x3b7/0x6e0 kernel/sched/idle.c:263
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355
rest_init+0x23b/0x371 init/main.c:451
arch_call_rest_init+0xe/0x1b
start_kernel+0x904/0x943 init/main.c:784
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242
---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: INFO: task hung in mpage_prepare_extent_to_map
2019-10-28 19:52 INFO: task hung in mpage_prepare_extent_to_map syzbot
@ 2019-10-28 20:14 ` Johannes Weiner
2019-10-28 22:15 ` Song Liu
0 siblings, 1 reply; 4+ messages in thread
From: Johannes Weiner @ 2019-10-28 20:14 UTC (permalink / raw)
To: syzbot
Cc: akpm, amir73il, darrick.wong, hughd, jack, jglisse, josef,
kirill.shutemov, linux-kernel, linux-mm, sfr, songliubraving,
syzkaller-bugs, william.kucharski, willy
On Mon, Oct 28, 2019 at 12:52:09PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 12d61c69 Add linux-next specific files for 20191024
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15a0fa97600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=afb75fd8c9fd5ed8
> dashboard link: https://syzkaller.appspot.com/bug?extid=efb9e48b9fbdc49bb34a
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13a63dc4e00000
>
> The bug was bisected to:
>
> commit 9c61acffe2b8833152041f7b6a02d1d0a17fd378
> Author: Song Liu <songliubraving@fb.com>
> Date: Wed Oct 23 00:24:28 2019 +0000
>
> mm,thp: recheck each page before collapsing file THP
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13eb6ec0e00000
> final crash: https://syzkaller.appspot.com/x/report.txt?x=101b6ec0e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17eb6ec0e00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+efb9e48b9fbdc49bb34a@syzkaller.appspotmail.com
> Fixes: 9c61acffe2b8 ("mm,thp: recheck each page before collapsing file THP")
>
> INFO: task khugepaged:1084 blocked for more than 143 seconds.
> Not tainted 5.4.0-rc4-next-20191024 #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> khugepaged D27568 1084 2 0x80004000
> Call Trace:
> context_switch kernel/sched/core.c:3384 [inline]
> __schedule+0x94a/0x1e70 kernel/sched/core.c:4069
> schedule+0xd9/0x260 kernel/sched/core.c:4136
> io_schedule+0x1c/0x70 kernel/sched/core.c:5780
> wait_on_page_bit_common mm/filemap.c:1175 [inline]
> __lock_page+0x422/0xab0 mm/filemap.c:1383
> lock_page include/linux/pagemap.h:480 [inline]
> mpage_prepare_extent_to_map+0xb3f/0xf90 fs/ext4/inode.c:2668
> ext4_writepages+0xb6a/0x2e70 fs/ext4/inode.c:2866
> ? 0xffffffff81000000
> do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
> __filemap_fdatawrite_range+0x2bc/0x3b0 mm/filemap.c:421
> __filemap_fdatawrite mm/filemap.c:429 [inline]
> filemap_flush+0x24/0x30 mm/filemap.c:456
This is a double locking deadlock. The page lock is already held when
we call into filemap_flush() here, and does another lock_page() in
write_cache_pages().
To fix it, we have to either initiate flushing before acquiring the
page lock, or simply skip over dirty pages.
Maybe doing vfs_fsync_range() from the madvise(HUGEPAGE) call isn't a
bad idea after all? (I had discussed this with Song off-list before.)
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: INFO: task hung in mpage_prepare_extent_to_map
2019-10-28 20:14 ` Johannes Weiner
@ 2019-10-28 22:15 ` Song Liu
2019-11-04 8:04 ` Dmitry Vyukov
0 siblings, 1 reply; 4+ messages in thread
From: Song Liu @ 2019-10-28 22:15 UTC (permalink / raw)
To: Johannes Weiner
Cc: syzbot, Andrew Morton, amir73il, darrick.wong, hughd, jack,
jglisse, Josef Bacik, kirill.shutemov, linux-kernel, linux-mm,
sfr, syzkaller-bugs, william.kucharski, willy
> On Oct 28, 2019, at 1:14 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Mon, Oct 28, 2019 at 12:52:09PM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 12d61c69 Add linux-next specific files for 20191024
>> git tree: linux-next
>> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D15a0fa97600000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=6-TXLGQxJcK1GdwMwa51423Y221rRncNiC_T09O0OLc&e=
>> kernel config: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_.config-3Fx-3Dafb75fd8c9fd5ed8&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=GuFgLJZOb7jtjZ5mDbkVT_zqtiVW4Py13e6Oq5CFxgY&e=
>> dashboard link: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3Defb9e48b9fbdc49bb34a&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=pF1hv-zGR8F378weGq9zxCE5ibI2_73qweMB_KuaZLM&e=
>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>> syz repro: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.syz-3Fx-3D13a63dc4e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=mI7ZOgrDWeG-p6vn2d_kj65a5g8J7exXJ2MIUUF84-w&e=
>>
>> The bug was bisected to:
>>
>> commit 9c61acffe2b8833152041f7b6a02d1d0a17fd378
>> Author: Song Liu <songliubraving@fb.com>
>> Date: Wed Oct 23 00:24:28 2019 +0000
>>
>> mm,thp: recheck each page before collapsing file THP
>>
>> bisection log: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_bisect.txt-3Fx-3D13eb6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=YtSUy5Dtjo6tek7CvwzMTPL40BJwOC6rEom-AkVx0SM&e=
>> final crash: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_report.txt-3Fx-3D101b6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=BvPJx3QSPHgsN12jSZci_MqW_VxYp-MZpQtogZjlJOo&e=
>> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D17eb6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=YPvxWpQDpk9MI9W6QCtxME64wmxL2CZ5ZtEkCn0nI0c&e=
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+efb9e48b9fbdc49bb34a@syzkaller.appspotmail.com
>> Fixes: 9c61acffe2b8 ("mm,thp: recheck each page before collapsing file THP")
>>
>> INFO: task khugepaged:1084 blocked for more than 143 seconds.
>> Not tainted 5.4.0-rc4-next-20191024 #0
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> khugepaged D27568 1084 2 0x80004000
>> Call Trace:
>> context_switch kernel/sched/core.c:3384 [inline]
>> __schedule+0x94a/0x1e70 kernel/sched/core.c:4069
>> schedule+0xd9/0x260 kernel/sched/core.c:4136
>> io_schedule+0x1c/0x70 kernel/sched/core.c:5780
>> wait_on_page_bit_common mm/filemap.c:1175 [inline]
>> __lock_page+0x422/0xab0 mm/filemap.c:1383
>> lock_page include/linux/pagemap.h:480 [inline]
>> mpage_prepare_extent_to_map+0xb3f/0xf90 fs/ext4/inode.c:2668
>> ext4_writepages+0xb6a/0x2e70 fs/ext4/inode.c:2866
>> ? 0xffffffff81000000
>> do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
>> __filemap_fdatawrite_range+0x2bc/0x3b0 mm/filemap.c:421
>> __filemap_fdatawrite mm/filemap.c:429 [inline]
>> filemap_flush+0x24/0x30 mm/filemap.c:456
>
> This is a double locking deadlock. The page lock is already held when
> we call into filemap_flush() here, and does another lock_page() in
> write_cache_pages().
>
> To fix it, we have to either initiate flushing before acquiring the
> page lock, or simply skip over dirty pages.
>
> Maybe doing vfs_fsync_range() from the madvise(HUGEPAGE) call isn't a
> bad idea after all? (I had discussed this with Song off-list before.)
Thanks syzbot and Johannes!
I just sent a quick fix, that just removes filemap_flush().
I will work on a better mechanism to flush the file.
Thanks,
Song
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: INFO: task hung in mpage_prepare_extent_to_map
2019-10-28 22:15 ` Song Liu
@ 2019-11-04 8:04 ` Dmitry Vyukov
0 siblings, 0 replies; 4+ messages in thread
From: Dmitry Vyukov @ 2019-11-04 8:04 UTC (permalink / raw)
To: Song Liu
Cc: Johannes Weiner, syzbot, Andrew Morton, amir73il, darrick.wong,
hughd, jack, jglisse, Josef Bacik, kirill.shutemov, linux-kernel,
linux-mm, sfr, syzkaller-bugs, william.kucharski, willy
On Mon, Oct 28, 2019 at 11:16 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Oct 28, 2019, at 1:14 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> >
> > On Mon, Oct 28, 2019 at 12:52:09PM -0700, syzbot wrote:
> >> Hello,
> >>
> >> syzbot found the following crash on:
> >>
> >> HEAD commit: 12d61c69 Add linux-next specific files for 20191024
> >> git tree: linux-next
> >> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D15a0fa97600000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=6-TXLGQxJcK1GdwMwa51423Y221rRncNiC_T09O0OLc&e=
> >> kernel config: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_.config-3Fx-3Dafb75fd8c9fd5ed8&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=GuFgLJZOb7jtjZ5mDbkVT_zqtiVW4Py13e6Oq5CFxgY&e=
> >> dashboard link: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3Defb9e48b9fbdc49bb34a&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=pF1hv-zGR8F378weGq9zxCE5ibI2_73qweMB_KuaZLM&e=
> >> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >> syz repro: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.syz-3Fx-3D13a63dc4e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=mI7ZOgrDWeG-p6vn2d_kj65a5g8J7exXJ2MIUUF84-w&e=
> >>
> >> The bug was bisected to:
> >>
> >> commit 9c61acffe2b8833152041f7b6a02d1d0a17fd378
> >> Author: Song Liu <songliubraving@fb.com>
> >> Date: Wed Oct 23 00:24:28 2019 +0000
> >>
> >> mm,thp: recheck each page before collapsing file THP
> >>
> >> bisection log: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_bisect.txt-3Fx-3D13eb6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=YtSUy5Dtjo6tek7CvwzMTPL40BJwOC6rEom-AkVx0SM&e=
> >> final crash: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_report.txt-3Fx-3D101b6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=BvPJx3QSPHgsN12jSZci_MqW_VxYp-MZpQtogZjlJOo&e=
> >> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D17eb6ec0e00000&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=YEaOe5RP2hLXAC4tKPLehAQsea0_3k3tI4DL32BcA-8&s=YPvxWpQDpk9MI9W6QCtxME64wmxL2CZ5ZtEkCn0nI0c&e=
> >>
> >> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> >> Reported-by: syzbot+efb9e48b9fbdc49bb34a@syzkaller.appspotmail.com
> >> Fixes: 9c61acffe2b8 ("mm,thp: recheck each page before collapsing file THP")
> >>
> >> INFO: task khugepaged:1084 blocked for more than 143 seconds.
> >> Not tainted 5.4.0-rc4-next-20191024 #0
> >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> >> khugepaged D27568 1084 2 0x80004000
> >> Call Trace:
> >> context_switch kernel/sched/core.c:3384 [inline]
> >> __schedule+0x94a/0x1e70 kernel/sched/core.c:4069
> >> schedule+0xd9/0x260 kernel/sched/core.c:4136
> >> io_schedule+0x1c/0x70 kernel/sched/core.c:5780
> >> wait_on_page_bit_common mm/filemap.c:1175 [inline]
> >> __lock_page+0x422/0xab0 mm/filemap.c:1383
> >> lock_page include/linux/pagemap.h:480 [inline]
> >> mpage_prepare_extent_to_map+0xb3f/0xf90 fs/ext4/inode.c:2668
> >> ext4_writepages+0xb6a/0x2e70 fs/ext4/inode.c:2866
> >> ? 0xffffffff81000000
> >> do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
> >> __filemap_fdatawrite_range+0x2bc/0x3b0 mm/filemap.c:421
> >> __filemap_fdatawrite mm/filemap.c:429 [inline]
> >> filemap_flush+0x24/0x30 mm/filemap.c:456
> >
> > This is a double locking deadlock. The page lock is already held when
> > we call into filemap_flush() here, and does another lock_page() in
> > write_cache_pages().
> >
> > To fix it, we have to either initiate flushing before acquiring the
> > page lock, or simply skip over dirty pages.
> >
> > Maybe doing vfs_fsync_range() from the madvise(HUGEPAGE) call isn't a
> > bad idea after all? (I had discussed this with Song off-list before.)
>
> Thanks syzbot and Johannes!
>
> I just sent a quick fix, that just removes filemap_flush().
>
> I will work on a better mechanism to flush the file.
Is this expected to reach linux-next soon?
It's still not there and in the past days this crash happened 17K+
times and effectively stalled linux-next testing:
https://syzkaller.appspot.com/bug?id=4a3b0ba28ec7d0277338be02e1331068504dc228
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-11-04 8:04 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-28 19:52 INFO: task hung in mpage_prepare_extent_to_map syzbot
2019-10-28 20:14 ` Johannes Weiner
2019-10-28 22:15 ` Song Liu
2019-11-04 8:04 ` Dmitry Vyukov
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