[syzbot] [exfat?] possible deadlock in exfat_evict_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6bfd2d442af5 Merge tag 'irq-core-2024-05-12' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=162ea96c980000
kernel config: https://syzkaller.appspot.com/x/.config?x=395546166dcfe360
dashboard link: https://syzkaller.appspot.com/bug?extid=412a392a2cd4a65e71db
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-6bfd2d44.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7ad901fe99c6/vmlinux-6bfd2d44.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8d6ef2df621f/bzImage-6bfd2d44.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+412a39...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-01893-g6bfd2d442af5 #0 Not tainted
------------------------------------------------------
kswapd0/112 is trying to acquire lock:
ffff88801d68c0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_evict_inode+0x25b/0x340 fs/exfat/inode.c:725

but task is already holding lock:
ffffffff8d9390c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
__fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
might_alloc include/linux/sched/mm.h:312 [inline]
slab_pre_alloc_hook mm/slub.c:3819 [inline]
slab_alloc_node mm/slub.c:3900 [inline]
__do_kmalloc_node mm/slub.c:4038 [inline]
__kmalloc+0xb5/0x440 mm/slub.c:4052
kmalloc_array include/linux/slab.h:665 [inline]
__exfat_get_dentry_set+0x81e/0xa90 fs/exfat/dir.c:816
exfat_get_dentry_set+0x36/0x210 fs/exfat/dir.c:859
exfat_get_uniname_from_ext_entry fs/exfat/dir.c:39 [inline]
exfat_readdir+0x950/0x1520 fs/exfat/dir.c:155
exfat_iterate+0x3c7/0xad0 fs/exfat/dir.c:261
wrap_directory_iterator+0xa5/0xe0 fs/readdir.c:67
iterate_dir+0x292/0x9e0 fs/readdir.c:110
__do_sys_getdents64 fs/readdir.c:409 [inline]
__se_sys_getdents64 fs/readdir.c:394 [inline]
__ia32_sys_getdents64+0x14f/0x2e0 fs/readdir.c:394
do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
__do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #0 (&sbi->s_lock#2){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
exfat_evict_inode+0x25b/0x340 fs/exfat/inode.c:725
evict+0x2ed/0x6c0 fs/inode.c:667
iput_final fs/inode.c:1741 [inline]
iput.part.0+0x5a8/0x7f0 fs/inode.c:1767
iput+0x5c/0x80 fs/inode.c:1757
dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
__dentry_kill+0x1d0/0x600 fs/dcache.c:603
shrink_kill fs/dcache.c:1048 [inline]
shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
super_cache_scan+0x32a/0x550 fs/super.c:221
do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
shrink_slab_memcg mm/shrinker.c:548 [inline]
shrink_slab+0xa87/0x1310 mm/shrinker.c:626
shrink_one+0x493/0x7c0 mm/vmscan.c:4774
shrink_many mm/vmscan.c:4835 [inline]
lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
shrink_node mm/vmscan.c:5894 [inline]
kswapd_shrink_node mm/vmscan.c:6704 [inline]
balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(&sbi->s_lock#2);
lock(fs_reclaim);
lock(&sbi->s_lock#2);

*** DEADLOCK ***

2 locks held by kswapd0/112:
#0: ffffffff8d9390c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782
#1: ffff88801d6880e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_trylock_shared fs/super.c:561 [inline]
#1: ffff88801d6880e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_cache_scan+0x96/0x550 fs/super.c:196

stack backtrace:
CPU: 2 PID: 112 Comm: kswapd0 Not tainted 6.9.0-syzkaller-01893-g6bfd2d442af5 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
check_noncircular+0x31a/0x400 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 kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
exfat_evict_inode+0x25b/0x340 fs/exfat/inode.c:725
evict+0x2ed/0x6c0 fs/inode.c:667
iput_final fs/inode.c:1741 [inline]
iput.part.0+0x5a8/0x7f0 fs/inode.c:1767
iput+0x5c/0x80 fs/inode.c:1757
dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
__dentry_kill+0x1d0/0x600 fs/dcache.c:603
shrink_kill fs/dcache.c:1048 [inline]
shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
super_cache_scan+0x32a/0x550 fs/super.c:221
do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
shrink_slab_memcg mm/shrinker.c:548 [inline]
shrink_slab+0xa87/0x1310 mm/shrinker.c:626
shrink_one+0x493/0x7c0 mm/vmscan.c:4774
shrink_many mm/vmscan.c:4835 [inline]
lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
shrink_node mm/vmscan.c:5894 [inline]
kswapd_shrink_node mm/vmscan.c:6704 [inline]
balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>


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