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SubjectINFO: task hung in xlog_grant_head_check
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Hello,

syzbot found the following crash on:

HEAD commit: 203ec2fed17a Merge tag 'armsoc-fixes' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11c1ad77800000
kernel config: https://syzkaller.appspot.com/x/.config?x=f3b4e30da84ec1ed
dashboard link: https://syzkaller.appspot.com/bug?extid=568245b88fbaedcb1959
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=122c7427800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10387057800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+568245b88fbaedcb1959@syzkaller.appspotmail.com

(ptrval): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 ................
(ptrval): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 ................
XFS (loop0): metadata I/O error in "xfs_trans_read_buf_map" at daddr 0x2
len 1 error 117
XFS (loop0): xfs_imap_lookup: xfs_ialloc_read_agi() returned error -117,
agno 0
XFS (loop0): failed to read root inode
INFO: task syz-executor060:4501 blocked for more than 120 seconds.
Not tainted 4.17.0-rc5+ #60
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor060 D17168 4501 4499 0x00000000
Call Trace:
context_switch kernel/sched/core.c:2859 [inline]
__schedule+0x801/0x1e30 kernel/sched/core.c:3501
schedule+0xef/0x430 kernel/sched/core.c:3545
xlog_grant_head_wait+0x260/0xf80 fs/xfs/xfs_log.c:275
xlog_grant_head_check+0x4d6/0x550 fs/xfs/xfs_log.c:337
xfs_log_reserve+0x398/0xd20 fs/xfs/xfs_log.c:466
xfs_log_unmount_write+0x2c4/0xfb0 fs/xfs/xfs_log.c:885
xfs_log_quiesce+0xf9/0x130 fs/xfs/xfs_log.c:1011
xfs_log_unmount+0x22/0xb0 fs/xfs/xfs_log.c:1025
xfs_log_mount_cancel+0x44/0x60 fs/xfs/xfs_log.c:828
xfs_mountfs+0x17d9/0x2b80 fs/xfs/xfs_mount.c:1041
xfs_fs_fill_super+0xdef/0x1560 fs/xfs/xfs_super.c:1734
mount_bdev+0x30c/0x3e0 fs/super.c:1164
xfs_fs_mount+0x34/0x40 fs/xfs/xfs_super.c:1801
mount_fs+0xae/0x328 fs/super.c:1267
vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:1027 [inline]
do_new_mount fs/namespace.c:2518 [inline]
do_mount+0x564/0x3070 fs/namespace.c:2848
ksys_mount+0x12d/0x140 fs/namespace.c:3064
__do_sys_mount fs/namespace.c:3078 [inline]
__se_sys_mount fs/namespace.c:3075 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x442d9a
RSP: 002b:00007ffc7a9dde88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442d9a
RDX: 0000000020000040 RSI: 0000000020000100 RDI: 00007ffc7a9dde90
RBP: 0000000000000004 R08: 00000000200001c0 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000401c00
R13: 0000000000401c90 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:
2 locks held by khungtaskd/893:
#0: (ptrval) (rcu_read_lock){....}, at:
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: (ptrval) (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60
kernel/hung_task.c:249
#1: (ptrval) (tasklist_lock){.+.+}, at:
debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
1 lock held by rsyslogd/4384:
#0: (ptrval) (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0
fs/file.c:766
2 locks held by getty/4474:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4475:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4476:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4477:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4478:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4479:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4480:
#0: (ptrval) (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (ptrval) (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
1 lock held by syz-executor060/4501:
#0: (ptrval) (&type->s_umount_key#36/1){+.+.}, at: alloc_super
fs/super.c:213 [inline]
#0: (ptrval) (&type->s_umount_key#36/1){+.+.}, at:
sget_userns+0x2dd/0xf00 fs/super.c:506

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 893 Comm: khungtaskd Not tainted 4.17.0-rc5+ #60
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+0x1b9/0x294 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x151/0x192 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:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0xc10/0xf60 kernel/hung_task.c:249
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


---
This bug is generated by a bot. It may contain errors.
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