[syzbot] [xfs?] possible deadlock in xfs_icwalk_ag

syzbot
2024-03-23T08:09:29Z

Hello,

syzbot found the following issue on:

HEAD commit: fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11525d81180000
kernel config: https://syzkaller.appspot.com/x/.config?x=fe78468a74fdc3b7
dashboard link: https://syzkaller.appspot.com/bug?extid=7766d4a620956dfe7070
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0f7abe4afac7/disk-fe46a7dd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/82598d09246c/vmlinux-fe46a7dd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/efa23788c875/bzImage-fe46a7dd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7766d4a620956dfe7070@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
kswapd0/89 is trying to acquire lock:
ffff88814af18118 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_reclaim_inode fs/xfs/xfs_icache.c:945 [inline]
ffff88814af18118 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1631 [inline]
ffff88814af18118 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_icwalk_ag+0x1216/0x1aa0 fs/xfs/xfs_icache.c:1713

but task is already holding lock:
ffffffff8e21f720 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6774 [inline]
ffffffff8e21f720 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb3f/0x36e0 mm/vmscan.c:7146

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (fs_reclaim){+.+.}-{0:0}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__fs_reclaim_acquire mm/page_alloc.c:3692 [inline]
fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3706
might_alloc include/linux/sched/mm.h:303 [inline]
slab_pre_alloc_hook mm/slub.c:3746 [inline]
slab_alloc_node mm/slub.c:3827 [inline]
kmem_cache_alloc+0x48/0x340 mm/slub.c:3852
radix_tree_node_alloc+0x8b/0x3c0 lib/radix-tree.c:276
radix_tree_extend+0x148/0x5c0 lib/radix-tree.c:425
__radix_tree_create lib/radix-tree.c:613 [inline]
radix_tree_insert+0x15c/0x680 lib/radix-tree.c:712
xfs_qm_dqget_cache_insert fs/xfs/xfs_dquot.c:826 [inline]
xfs_qm_dqget+0x2d4/0x640 fs/xfs/xfs_dquot.c:901
xfs_qm_vop_dqalloc+0x5a3/0xef0 fs/xfs/xfs_qm.c:1730
xfs_setattr_nonsize+0x410/0xea0 fs/xfs/xfs_iops.c:707
xfs_vn_setattr+0x2d1/0x320 fs/xfs/xfs_iops.c:1027
notify_change+0xb9f/0xe70 fs/attr.c:497
chown_common+0x501/0x850 fs/open.c:790
vfs_fchown fs/open.c:858 [inline]
ksys_fchown+0xea/0x160 fs/open.c:869
__do_sys_fchown fs/open.c:877 [inline]
__se_sys_fchown fs/open.c:875 [inline]
__x64_sys_fchown+0x7a/0x90 fs/open.c:875
do_syscall_64+0xfd/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #1 (&qinf->qi_tree_lock){+.+.}-{3:3}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
xfs_qm_dqget_cache_lookup+0x30/0x870 fs/xfs/xfs_dquot.c:784
xfs_qm_dqget_inode+0x353/0xaa0 fs/xfs/xfs_dquot.c:986
xfs_qm_dqattach_one+0x185/0x5e0 fs/xfs/xfs_qm.c:278
xfs_qm_dqattach_locked+0x3d1/0x4e0 fs/xfs/xfs_qm.c:329
xfs_qm_vop_dqalloc+0x3fd/0xef0 fs/xfs/xfs_qm.c:1710
xfs_create+0x568/0x1300 fs/xfs/xfs_inode.c:1041
xfs_generic_create+0x495/0xd70 fs/xfs/xfs_iops.c:199
lookup_open fs/namei.c:3497 [inline]
open_last_lookups fs/namei.c:3566 [inline]
path_openat+0x1427/0x3240 fs/namei.c:3796
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_open fs/open.c:1429 [inline]
__se_sys_open fs/open.c:1425 [inline]
__x64_sys_open+0x225/0x270 fs/open.c:1425
do_syscall_64+0xfd/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #0 (&xfs_dir_ilock_class){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
down_write_nested+0x3d/0x50 kernel/locking/rwsem.c:1695
xfs_reclaim_inode fs/xfs/xfs_icache.c:945 [inline]
xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1631 [inline]
xfs_icwalk_ag+0x1216/0x1aa0 fs/xfs/xfs_icache.c:1713
xfs_icwalk fs/xfs/xfs_icache.c:1762 [inline]
xfs_reclaim_inodes_nr+0x257/0x360 fs/xfs/xfs_icache.c:1011
super_cache_scan+0x411/0x4b0 fs/super.c:227
do_shrink_slab+0x6d2/0x1140 mm/shrinker.c:435
shrink_slab+0x1092/0x14d0 mm/shrinker.c:662
shrink_one+0x423/0x7f0 mm/vmscan.c:4767
shrink_many mm/vmscan.c:4828 [inline]
lru_gen_shrink_node mm/vmscan.c:4929 [inline]
shrink_node+0x37b8/0x3e70 mm/vmscan.c:5888
kswapd_shrink_node mm/vmscan.c:6696 [inline]
balance_pgdat mm/vmscan.c:6886 [inline]
kswapd+0x17d1/0x36e0 mm/vmscan.c:7146
kthread+0x2f2/0x390 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

other info that might help us debug this:

Chain exists of:
&xfs_dir_ilock_class --> &qinf->qi_tree_lock --> fs_reclaim

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(&qinf->qi_tree_lock);
lock(fs_reclaim);
lock(&xfs_dir_ilock_class);

*** DEADLOCK ***

2 locks held by kswapd0/89:
#0: ffffffff8e21f720 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6774 [inline]
#0: ffffffff8e21f720 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb3f/0x36e0 mm/vmscan.c:7146
#1: ffff88807c6c60e0 (&type->s_umount_key#55){.+.+}-{3:3}, at: super_trylock_shared fs/super.c:561 [inline]
#1: ffff88807c6c60e0 (&type->s_umount_key#55){.+.+}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 1 PID: 89 Comm: kswapd0 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
down_write_nested+0x3d/0x50 kernel/locking/rwsem.c:1695
xfs_reclaim_inode fs/xfs/xfs_icache.c:945 [inline]
xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1631 [inline]
xfs_icwalk_ag+0x1216/0x1aa0 fs/xfs/xfs_icache.c:1713
xfs_icwalk fs/xfs/xfs_icache.c:1762 [inline]
xfs_reclaim_inodes_nr+0x257/0x360 fs/xfs/xfs_icache.c:1011
super_cache_scan+0x411/0x4b0 fs/super.c:227
do_shrink_slab+0x6d2/0x1140 mm/shrinker.c:435
shrink_slab+0x1092/0x14d0 mm/shrinker.c:662
shrink_one+0x423/0x7f0 mm/vmscan.c:4767
shrink_many mm/vmscan.c:4828 [inline]
lru_gen_shrink_node mm/vmscan.c:4929 [inline]
shrink_node+0x37b8/0x3e70 mm/vmscan.c:5888
kswapd_shrink_node mm/vmscan.c:6696 [inline]
balance_pgdat mm/vmscan.c:6886 [inline]
kswapd+0x17d1/0x36e0 mm/vmscan.c:7146
kthread+0x2f2/0x390 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
</TASK>

---
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