Message-ID: <6751260d.050a0220.17bd51.0085.GAE@google.com>
Date: Wed, 04 Dec 2024 20:03:25 -0800
From: syzbot <syzbot+71d80f05e434f9bfaaec@...kaller.appspotmail.com>
To: clm@...com, dsterba@...e.com, josef@...icpanda.com, 
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [btrfs?] possible deadlock in __btrfs_commit_inode_delayed_items

Hello,

syzbot found the following issue on:

HEAD commit:    f486c8aa16b8 Add linux-next specific files for 20241128
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=111705e8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e348a4873516af92
dashboard link: https://syzkaller.appspot.com/bug?extid=71d80f05e434f9bfaaec
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/beb58ebb63cf/disk-f486c8aa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b241b5609e64/vmlinux-f486c8aa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c9d817f665f2/bzImage-f486c8aa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+71d80f05e434f9bfaaec@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.12.0-next-20241128-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u8:12/6861 is trying to acquire lock:
ffff88803171b3b8 (btrfs-tree-01){++++}-{4:4}, at: btrfs_tree_read_lock_nested+0x2f/0x250 fs/btrfs/locking.c:146

but task is already holding lock:
ffff888071adc860 (&delayed_node->mutex){+.+.}-{4:4}, at: btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:830 [inline]
ffff888071adc860 (&delayed_node->mutex){+.+.}-{4:4}, at: __btrfs_commit_inode_delayed_items+0x1c4/0x24a0 fs/btrfs/delayed-inode.c:1126

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&delayed_node->mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       __btrfs_release_delayed_node+0xa5/0xaf0 fs/btrfs/delayed-inode.c:268
       btrfs_evict_inode+0x752/0x1080 fs/btrfs/inode.c:5374
       evict+0x4e8/0x9a0 fs/inode.c:796
       dispose_list fs/inode.c:845 [inline]
       prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
       super_cache_scan+0x38c/0x4b0 fs/super.c:223
       do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
       shrink_slab_memcg mm/shrinker.c:550 [inline]
       shrink_slab+0x878/0x14d0 mm/shrinker.c:628
       shrink_one+0x43b/0x850 mm/vmscan.c:4836
       shrink_many mm/vmscan.c:4897 [inline]
       lru_gen_shrink_node mm/vmscan.c:4975 [inline]
       shrink_node+0x37c5/0x3e50 mm/vmscan.c:5956
       kswapd_shrink_node mm/vmscan.c:6785 [inline]
       balance_pgdat mm/vmscan.c:6977 [inline]
       kswapd+0x1ca9/0x36f0 mm/vmscan.c:7246
       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

-> #3 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __fs_reclaim_acquire mm/page_alloc.c:3887 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3901
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4055 [inline]
       slab_alloc_node mm/slub.c:4133 [inline]
       __kmalloc_cache_noprof+0x41/0x390 mm/slub.c:4309
       kmalloc_noprof include/linux/slab.h:901 [inline]
       kzalloc_noprof include/linux/slab.h:1037 [inline]
       kobject_uevent_env+0x28b/0x8e0 lib/kobject_uevent.c:540
       loop_set_size drivers/block/loop.c:233 [inline]
       loop_set_status+0x5f0/0x8f0 drivers/block/loop.c:1285
       lo_ioctl+0xcbc/0x1f50
       blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       bio_queue_enter block/blk.h:75 [inline]
       blk_mq_submit_bio+0x1536/0x2390 block/blk-mq.c:3091
       __submit_bio+0x2c6/0x560 block/blk-core.c:629
       __submit_bio_noacct_mq block/blk-core.c:710 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:739
       btrfs_submit_chunk fs/btrfs/bio.c:745 [inline]
       btrfs_submit_bbio+0xf93/0x18e0 fs/btrfs/bio.c:773
       read_extent_buffer_pages+0x65a/0x910 fs/btrfs/extent_io.c:3558
       btrfs_read_extent_buffer+0xd9/0x770 fs/btrfs/disk-io.c:229
       read_block_for_search+0x79e/0xbb0 fs/btrfs/ctree.c:1619
       btrfs_search_slot+0x121b/0x3150 fs/btrfs/ctree.c:2236
       btrfs_init_root_free_objectid+0x148/0x330 fs/btrfs/disk-io.c:4837
       btrfs_init_fs_root fs/btrfs/disk-io.c:1137 [inline]
       btrfs_get_root_ref+0x5d7/0xc30 fs/btrfs/disk-io.c:1364
       btrfs_get_fs_root fs/btrfs/disk-io.c:1416 [inline]
       open_ctree+0x2470/0x2a30 fs/btrfs/disk-io.c:3532
       btrfs_fill_super fs/btrfs/super.c:972 [inline]
       btrfs_get_tree_super fs/btrfs/super.c:1894 [inline]
       btrfs_get_tree+0x1274/0x1a10 fs/btrfs/super.c:2105
       vfs_get_tree+0x90/0x2b0 fs/super.c:1814
       fc_mount+0x1b/0xb0 fs/namespace.c:1231
       btrfs_get_tree_subvol fs/btrfs/super.c:2068 [inline]
       btrfs_get_tree+0x65b/0x1a10 fs/btrfs/super.c:2106
       vfs_get_tree+0x90/0x2b0 fs/super.c:1814
       do_new_mount+0x2be/0xb40 fs/namespace.c:3507
       do_mount fs/namespace.c:3847 [inline]
       __do_sys_mount fs/namespace.c:4057 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs-tree-00){++++}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_read_nested+0xb5/0xa50 kernel/locking/rwsem.c:1649
       btrfs_tree_read_lock_nested+0x2f/0x250 fs/btrfs/locking.c:146
       btrfs_tree_read_lock fs/btrfs/locking.h:178 [inline]
       read_block_for_search+0x718/0xbb0 fs/btrfs/ctree.c:1613
       btrfs_search_slot+0x121b/0x3150 fs/btrfs/ctree.c:2236
       btrfs_init_root_free_objectid+0x148/0x330 fs/btrfs/disk-io.c:4837
       btrfs_init_fs_root fs/btrfs/disk-io.c:1137 [inline]
       btrfs_get_root_ref+0x5d7/0xc30 fs/btrfs/disk-io.c:1364
       btrfs_get_fs_root fs/btrfs/disk-io.c:1416 [inline]
       open_ctree+0x2470/0x2a30 fs/btrfs/disk-io.c:3532
       btrfs_fill_super fs/btrfs/super.c:972 [inline]
       btrfs_get_tree_super fs/btrfs/super.c:1894 [inline]
       btrfs_get_tree+0x1274/0x1a10 fs/btrfs/super.c:2105
       vfs_get_tree+0x90/0x2b0 fs/super.c:1814
       fc_mount+0x1b/0xb0 fs/namespace.c:1231
       btrfs_get_tree_subvol fs/btrfs/super.c:2068 [inline]
       btrfs_get_tree+0x65b/0x1a10 fs/btrfs/super.c:2106
       vfs_get_tree+0x90/0x2b0 fs/super.c:1814
       do_new_mount+0x2be/0xb40 fs/namespace.c:3507
       do_mount fs/namespace.c:3847 [inline]
       __do_sys_mount fs/namespace.c:4057 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (btrfs-tree-01){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_read_nested+0xb5/0xa50 kernel/locking/rwsem.c:1649
       btrfs_tree_read_lock_nested+0x2f/0x250 fs/btrfs/locking.c:146
       btrfs_tree_read_lock fs/btrfs/locking.h:178 [inline]
       btrfs_read_lock_root_node+0x3f/0xd0 fs/btrfs/locking.c:267
       btrfs_search_slot_get_root fs/btrfs/ctree.c:1790 [inline]
       btrfs_search_slot+0x4f7/0x3150 fs/btrfs/ctree.c:2112
       btrfs_insert_empty_items+0x9c/0x1a0 fs/btrfs/ctree.c:4350
       btrfs_insert_delayed_item fs/btrfs/delayed-inode.c:758 [inline]
       btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:836 [inline]
       __btrfs_commit_inode_delayed_items+0xd5d/0x24a0 fs/btrfs/delayed-inode.c:1126
       __btrfs_run_delayed_items+0x213/0x490 fs/btrfs/delayed-inode.c:1171
       flush_space+0x24a/0xcf0 fs/btrfs/space-info.c:775
       btrfs_async_reclaim_metadata_space+0x113/0x350 fs/btrfs/space-info.c:1105
       process_one_work kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
       worker_thread+0x870/0xd30 kernel/workqueue.c:3391
       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:

Chain exists of:
  btrfs-tree-01 --> fs_reclaim --> &delayed_node->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&delayed_node->mutex);
                               lock(fs_reclaim);
                               lock(&delayed_node->mutex);
  rlock(btrfs-tree-01);

 *** DEADLOCK ***

5 locks held by kworker/u8:12/6861:
 #0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
 #1: ffffc9000369fd00 ((work_completion)(&fs_info->async_reclaim_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc9000369fd00 ((work_completion)(&fs_info->async_reclaim_work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
 #2: ffff888034ba2470 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x405/0xda0 fs/btrfs/transaction.c:288
 #3: ffff888034ba2498 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x405/0xda0 fs/btrfs/transaction.c:288
 #4: ffff888071adc860 (&delayed_node->mutex){+.+.}-{4:4}, at: btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:830 [inline]
 #4: ffff888071adc860 (&delayed_node->mutex){+.+.}-{4:4}, at: __btrfs_commit_inode_delayed_items+0x1c4/0x24a0 fs/btrfs/delayed-inode.c:1126

stack backtrace:
CPU: 0 UID: 0 PID: 6861 Comm: kworker/u8:12 Not tainted 6.12.0-next-20241128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 down_read_nested+0xb5/0xa50 kernel/locking/rwsem.c:1649
 btrfs_tree_read_lock_nested+0x2f/0x250 fs/btrfs/locking.c:146
 btrfs_tree_read_lock fs/btrfs/locking.h:178 [inline]
 btrfs_read_lock_root_node+0x3f/0xd0 fs/btrfs/locking.c:267
 btrfs_search_slot_get_root fs/btrfs/ctree.c:1790 [inline]
 btrfs_search_slot+0x4f7/0x3150 fs/btrfs/ctree.c:2112
 btrfs_insert_empty_items+0x9c/0x1a0 fs/btrfs/ctree.c:4350
 btrfs_insert_delayed_item fs/btrfs/delayed-inode.c:758 [inline]
 btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:836 [inline]
 __btrfs_commit_inode_delayed_items+0xd5d/0x24a0 fs/btrfs/delayed-inode.c:1126
 __btrfs_run_delayed_items+0x213/0x490 fs/btrfs/delayed-inode.c:1171
 flush_space+0x24a/0xcf0 fs/btrfs/space-info.c:775
 btrfs_async_reclaim_metadata_space+0x113/0x350 fs/btrfs/space-info.c:1105
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 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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