Message-ID: <6935c265.a70a0220.38f243.0067.GAE@google.com>
Date: Sun, 07 Dec 2025 10:07:33 -0800
From: syzbot <syzbot+a8a73f25200041b89d40@...kaller.appspotmail.com>
To: cem@...nel.org, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [xfs?] possible deadlock in xfs_can_free_eofblocks (3)

Hello,

syzbot found the following issue on:

HEAD commit:    c06c303832ec ocfs2: fix xattr array entry __counted_by error
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1688a992580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d3ce1cfe3996fc8b
dashboard link: https://syzkaller.appspot.com/bug?extid=a8a73f25200041b89d40
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c06c3038.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aa14148a2ef4/vmlinux-c06c3038.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d2d5f3a106bf/bzImage-c06c3038.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a8a73f25200041b89d40@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/79 is trying to acquire lock:
ffff88800083d798 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_can_free_eofblocks+0x693/0x8e0 fs/xfs/xfs_bmap_util.c:562

but task is already holding lock:
ffffffff8e251780 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6973 [inline]
ffffffff8e251780 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x92a/0x2820 mm/vmscan.c:7352

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:4301 [inline]
       fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4899 [inline]
       slab_alloc_node mm/slub.c:5234 [inline]
       __kmalloc_cache_noprof+0x40/0x700 mm/slub.c:5766
       kmalloc_noprof include/linux/slab.h:957 [inline]
       iomap_fill_dirty_folios+0xf4/0x260 fs/iomap/buffered-io.c:1557
       xfs_buffered_write_iomap_begin+0xa23/0x1a70 fs/xfs/xfs_iomap.c:1857
       iomap_iter+0x5ef/0xeb0 fs/iomap/iter.c:110
       iomap_zero_range+0x1cc/0xa30 fs/iomap/buffered-io.c:1590
       xfs_zero_range+0x9a/0x100 fs/xfs/xfs_iomap.c:2289
       xfs_setattr_size+0x48b/0xed0 fs/xfs/xfs_iops.c:993
       __xfs_file_fallocate+0x10ca/0x15f0 include/linux/fs.h:-1
       xfs_file_fallocate+0x27b/0x340 fs/xfs/xfs_file.c:1462
       vfs_fallocate+0x669/0x7e0 fs/open.c:339
       ksys_fallocate fs/open.c:363 [inline]
       __do_sys_fallocate fs/open.c:368 [inline]
       __se_sys_fallocate fs/open.c:366 [inline]
       __x64_sys_fallocate+0xc0/0x110 fs/open.c:366
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&xfs_nondir_ilock_class){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
       down_read_nested+0x49/0x2e0 kernel/locking/rwsem.c:1662
       xfs_can_free_eofblocks+0x693/0x8e0 fs/xfs/xfs_bmap_util.c:562
       xfs_inode_mark_reclaimable+0x21d/0x1030 fs/xfs/xfs_icache.c:2244
       destroy_inode fs/inode.c:396 [inline]
       evict+0x8aa/0xae0 fs/inode.c:861
       dispose_list fs/inode.c:879 [inline]
       prune_icache_sb+0x21b/0x2c0 fs/inode.c:1027
       super_cache_scan+0x39b/0x4b0 fs/super.c:224
       do_shrink_slab+0x6df/0x10d0 mm/shrinker.c:437
       shrink_slab_memcg mm/shrinker.c:550 [inline]
       shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
       shrink_one+0x2d9/0x720 mm/vmscan.c:4919
       shrink_many mm/vmscan.c:4980 [inline]
       lru_gen_shrink_node mm/vmscan.c:5058 [inline]
       shrink_node+0x2f7d/0x35b0 mm/vmscan.c:6045
       kswapd_shrink_node mm/vmscan.c:6899 [inline]
       balance_pgdat mm/vmscan.c:7082 [inline]
       kswapd+0x145a/0x2820 mm/vmscan.c:7352
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&xfs_nondir_ilock_class);
                               lock(fs_reclaim);
  rlock(&xfs_nondir_ilock_class);

 *** DEADLOCK ***

2 locks held by kswapd0/79:
 #0: ffffffff8e251780 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6973 [inline]
 #0: ffffffff8e251780 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x92a/0x2820 mm/vmscan.c:7352
 #1: ffff88803639a0e0 (&type->s_umount_key#51){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:563 [inline]
 #1: ffff88803639a0e0 (&type->s_umount_key#51){.+.+}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197

stack backtrace:
CPU: 0 UID: 0 PID: 79 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
 down_read_nested+0x49/0x2e0 kernel/locking/rwsem.c:1662
 xfs_can_free_eofblocks+0x693/0x8e0 fs/xfs/xfs_bmap_util.c:562
 xfs_inode_mark_reclaimable+0x21d/0x1030 fs/xfs/xfs_icache.c:2244
 destroy_inode fs/inode.c:396 [inline]
 evict+0x8aa/0xae0 fs/inode.c:861
 dispose_list fs/inode.c:879 [inline]
 prune_icache_sb+0x21b/0x2c0 fs/inode.c:1027
 super_cache_scan+0x39b/0x4b0 fs/super.c:224
 do_shrink_slab+0x6df/0x10d0 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
 shrink_one+0x2d9/0x720 mm/vmscan.c:4919
 shrink_many mm/vmscan.c:4980 [inline]
 lru_gen_shrink_node mm/vmscan.c:5058 [inline]
 shrink_node+0x2f7d/0x35b0 mm/vmscan.c:6045
 kswapd_shrink_node mm/vmscan.c:6899 [inline]
 balance_pgdat mm/vmscan.c:7082 [inline]
 kswapd+0x145a/0x2820 mm/vmscan.c:7352
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>


---
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