[syzbot] [xfs?] possible deadlock in xfs_icwalk_ag (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9ed46da14b9b Add linux-next specific files for 20240412
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=100fbfcb180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7ea0abc478c49859
dashboard link: https://syzkaller.appspot.com/bug?extid=4248e91deb3db78358a2
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/fc649744d68c/disk-9ed46da1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11eab7b9945d/vmlinux-9ed46da1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e7885afd198d/bzImage-9ed46da1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4248e9...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc3-next-20240412-syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/88 is trying to acquire lock:
ffff88807b8bc6d8 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_reclaim_inode fs/xfs/xfs_icache.c:945 [inline]
ffff88807b8bc6d8 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1631 [inline]
ffff88807b8bc6d8 (&xfs_dir_ilock_class){++++}-{3:3}, at: xfs_icwalk_ag+0x120e/0x1ad0 fs/xfs/xfs_icache.c:1713

but task is already holding lock:
ffffffff8e429e80 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6819 [inline]
ffffffff8e429e80 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbe8/0x38a0 mm/vmscan.c:7201

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__fs_reclaim_acquire mm/page_alloc.c:3825 [inline]
fs_reclaim_acquire+0x88/0x140 mm/page_alloc.c:3839
might_alloc include/linux/sched/mm.h:334 [inline]
slab_pre_alloc_hook mm/slub.c:3847 [inline]
slab_alloc_node mm/slub.c:3937 [inline]
__do_kmalloc_node mm/slub.c:4077 [inline]
__kmalloc_noprof+0xae/0x400 mm/slub.c:4091
kmalloc_noprof include/linux/slab.h:664 [inline]
xfs_attr_shortform_list+0x6f1/0x17b0 fs/xfs/xfs_attr_list.c:115
xfs_attr_list_ilocked fs/xfs/xfs_attr_list.c:527 [inline]
xfs_attr_list+0x25b/0x350 fs/xfs/xfs_attr_list.c:547
xfs_vn_listxattr+0x1d2/0x2c0 fs/xfs/xfs_xattr.c:314
vfs_listxattr fs/xattr.c:493 [inline]
listxattr+0x107/0x290 fs/xattr.c:840
path_listxattr fs/xattr.c:864 [inline]
__do_sys_listxattr fs/xattr.c:876 [inline]
__se_sys_listxattr fs/xattr.c:873 [inline]
__x64_sys_listxattr+0x176/0x240 fs/xattr.c:873
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #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+0x1ed/0x550 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+0x120e/0x1ad0 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+0x40f/0x4b0 fs/super.c:227
do_shrink_slab+0x705/0x1160 mm/shrinker.c:435
shrink_slab+0x1092/0x14d0 mm/shrinker.c:662
shrink_one+0x453/0x880 mm/vmscan.c:4809
shrink_many mm/vmscan.c:4870 [inline]
lru_gen_shrink_node mm/vmscan.c:4970 [inline]
shrink_node+0x3b17/0x4310 mm/vmscan.c:5929
kswapd_shrink_node mm/vmscan.c:6741 [inline]
balance_pgdat mm/vmscan.c:6932 [inline]
kswapd+0x1882/0x38a0 mm/vmscan.c:7201
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/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(&xfs_dir_ilock_class);
lock(fs_reclaim);
lock(&xfs_dir_ilock_class);

*** DEADLOCK ***

2 locks held by kswapd0/88:
#0: ffffffff8e429e80 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6819 [inline]
#0: ffffffff8e429e80 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbe8/0x38a0 mm/vmscan.c:7201
#1: ffff8880866840e0 (&type->s_umount_key#74){++++}-{3:3}, at: super_trylock_shared fs/super.c:561 [inline]
#1: ffff8880866840e0 (&type->s_umount_key#74){++++}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 1 PID: 88 Comm: kswapd0 Not tainted 6.9.0-rc3-next-20240412-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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+0x1ed/0x550 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+0x120e/0x1ad0 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+0x40f/0x4b0 fs/super.c:227
do_shrink_slab+0x705/0x1160 mm/shrinker.c:435
shrink_slab+0x1092/0x14d0 mm/shrinker.c:662
shrink_one+0x453/0x880 mm/vmscan.c:4809
shrink_many mm/vmscan.c:4870 [inline]
lru_gen_shrink_node mm/vmscan.c:4970 [inline]
shrink_node+0x3b17/0x4310 mm/vmscan.c:5929
kswapd_shrink_node mm/vmscan.c:6741 [inline]
balance_pgdat mm/vmscan.c:6932 [inline]
kswapd+0x1882/0x38a0 mm/vmscan.c:7201
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/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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