syzbot

loop0: detected capacity change from 0 to 32768
=======================================================
WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
XFS (loop0): Mounting V5 Filesystem bfdc47fc-10d8-4eed-a562-11a831b3f791
XFS (loop0): Ending clean mount
XFS (loop0): Quotacheck needed: Please wait.
XFS (loop0): Quotacheck: Done.
loop0: detected capacity change from 32768 to 0
======================================================
WARNING: possible circular locking dependency detected
6.12.0-syzkaller-09073-g9f16d5e6f220 #0 Not tainted
------------------------------------------------------
syz.0.0/5332 is trying to acquire lock:
ffffffff8ea3f480 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline]
ffffffff8ea3f480 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4036 [inline]
ffffffff8ea3f480 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4114 [inline]
ffffffff8ea3f480 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x3d/0x2c0 mm/slub.c:4290

but task is already holding lock:
ffff888033e81e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #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+0x1536/0x23a0 block/blk-mq.c:3092
       __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
       xfs_buf_ioapply_map+0x461/0x5d0 fs/xfs/xfs_buf.c:1586
       _xfs_buf_ioapply+0x307/0x660 fs/xfs/xfs_buf.c:1674
       __xfs_buf_submit+0x34f/0x7f0 fs/xfs/xfs_buf.c:1758
       xfs_buf_submit fs/xfs/xfs_buf.c:61 [inline]
       _xfs_buf_read fs/xfs/xfs_buf.c:809 [inline]
       xfs_buf_read_map+0x431/0xa60 fs/xfs/xfs_buf.c:873
       xfs_trans_read_buf_map+0x260/0xad0 fs/xfs/xfs_trans_buf.c:304
       xfs_trans_read_buf fs/xfs/xfs_trans.h:213 [inline]
       xfs_read_agf+0x2dc/0x630 fs/xfs/libxfs/xfs_alloc.c:3378
       xfs_alloc_read_agf+0x196/0xbe0 fs/xfs/libxfs/xfs_alloc.c:3413
       xfs_alloc_fix_freelist+0x608/0x1bd0 fs/xfs/libxfs/xfs_alloc.c:2877
       xfs_alloc_vextent_prepare_ag+0xf9/0x6b0 fs/xfs/libxfs/xfs_alloc.c:3543
       xfs_alloc_vextent_iterate_ags+0x141/0x960 fs/xfs/libxfs/xfs_alloc.c:3727
       xfs_alloc_vextent_start_ag+0x3f6/0x950 fs/xfs/libxfs/xfs_alloc.c:3816
       xfs_bmap_btalloc_best_length fs/xfs/libxfs/xfs_bmap.c:3768 [inline]
       xfs_bmap_btalloc fs/xfs/libxfs/xfs_bmap.c:3813 [inline]
       xfs_bmapi_allocate+0x18fa/0x3450 fs/xfs/libxfs/xfs_bmap.c:4226
       xfs_bmapi_write+0xbac/0x1b40 fs/xfs/libxfs/xfs_bmap.c:4555
       xfs_dquot_disk_alloc+0x5f4/0xe20 fs/xfs/xfs_dquot.c:355
       xfs_qm_dqread+0x1a3/0x650 fs/xfs/xfs_dquot.c:694
       xfs_qm_dqget+0x2bb/0x6f0 fs/xfs/xfs_dquot.c:906
       xfs_qm_quotacheck_dqadjust+0xea/0x5a0 fs/xfs/xfs_qm.c:1297
       xfs_qm_dqusage_adjust+0x5e1/0x850 fs/xfs/xfs_qm.c:1419
       xfs_iwalk_ag_recs+0x4e1/0x820 fs/xfs/xfs_iwalk.c:209
       xfs_iwalk_run_callbacks+0x218/0x470 fs/xfs/xfs_iwalk.c:370
       xfs_iwalk_ag+0xa9a/0xbb0 fs/xfs/xfs_iwalk.c:476
       xfs_iwalk_ag_work+0xfb/0x1b0 fs/xfs/xfs_iwalk.c:625
       xfs_pwork_work+0x7f/0x190 fs/xfs/xfs_pwork.c:47
       process_one_work kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa63/0x1850 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

-> #1 (&xfs_nondir_ilock_class){++++}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_write_nested+0xa2/0x220 kernel/locking/rwsem.c:1693
       xfs_reclaim_inode fs/xfs/xfs_icache.c:1037 [inline]
       xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1729 [inline]
       xfs_icwalk_ag+0x120e/0x1ad0 fs/xfs/xfs_icache.c:1811
       xfs_icwalk fs/xfs/xfs_icache.c:1859 [inline]
       xfs_reclaim_inodes_nr+0x2b0/0x390 fs/xfs/xfs_icache.c:1103
       super_cache_scan+0x40f/0x4b0 fs/super.c:227
       do_shrink_slab+0x701/0x1160 mm/shrinker.c:437
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
       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+0x1ca9/0x3700 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

-> #0 (fs_reclaim){+.+.}-{0:0}:
       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
       __fs_reclaim_acquire mm/page_alloc.c:3851 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3865
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4036 [inline]
       slab_alloc_node mm/slub.c:4114 [inline]
       __kmalloc_cache_noprof+0x3d/0x2c0 mm/slub.c:4290
       kmalloc_noprof include/linux/slab.h:879 [inline]
       kzalloc_noprof include/linux/slab.h:1015 [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

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> &xfs_nondir_ilock_class --> &q->q_usage_counter(io)#17

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&q->q_usage_counter(io)#17);
                               lock(&xfs_nondir_ilock_class);
                               lock(&q->q_usage_counter(io)#17);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz.0.0/5332:
 #0: ffff88801fb53360 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0x8f0 drivers/block/loop.c:1251
 #1: ffff888033e81e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267
 #2: ffff888033e81e38 (&q->q_usage_counter(queue)){+.+.}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267

stack backtrace:
CPU: 0 UID: 0 PID: 5332 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-09073-g9f16d5e6f220 #0
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 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
 __fs_reclaim_acquire mm/page_alloc.c:3851 [inline]
 fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3865
 might_alloc include/linux/sched/mm.h:318 [inline]
 slab_pre_alloc_hook mm/slub.c:4036 [inline]
 slab_alloc_node mm/slub.c:4114 [inline]
 __kmalloc_cache_noprof+0x3d/0x2c0 mm/slub.c:4290
 kmalloc_noprof include/linux/slab.h:879 [inline]
 kzalloc_noprof include/linux/slab.h:1015 [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
RIP: 0033:0x7f9068d7e819
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9069be4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9068f35fa0 RCX: 00007f9068d7e819
RDX: 00000000200000c0 RSI: 0000000000004c02 RDI: 0000000000000009
RBP: 00007f9068df175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9068f35fa0 R15: 00007fff1321d308
 </TASK>
syz.0.0 (5332) used greatest stack depth: 18416 bytes left