loop1: detected capacity change from 0 to 512
EXT4-fs (loop1): mounted filesystem without journal. Quota mode: writeback.
======================================================
WARNING: possible circular locking dependency detected
6.1.142-syzkaller #0 Not tainted
------------------------------------------------------
syz.1.668/6713 is trying to acquire lock:
ffff0000e1e180a8 (&dquot->dq_lock){+.+.}-{3:3}, at: dquot_commit+0x50/0x1c4 fs/quota/dquot.c:507

but task is already holding lock:
ffff0000dfd7f0e0 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_map_blocks+0x7c4/0x1770 fs/ext4/inode.c:672

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&ei->i_data_sem/2){++++}-{3:3}:
       down_read+0x64/0x304 kernel/locking/rwsem.c:1520
       ext4_map_blocks+0x278/0x1770 fs/ext4/inode.c:604
       ext4_getblk+0x170/0x654 fs/ext4/inode.c:890
       ext4_bread+0x3c/0x1b0 fs/ext4/inode.c:946
       ext4_quota_write+0x228/0x51c fs/ext4/super.c:7201
       write_blk fs/quota/quota_tree.c:70 [inline]
       get_free_dqblk+0x284/0x574 fs/quota/quota_tree.c:136
       do_insert_tree+0x1c4/0xc38 fs/quota/quota_tree.c:347
       do_insert_tree+0x794/0xc38 fs/quota/quota_tree.c:402
       do_insert_tree+0x768/0xc38 fs/quota/quota_tree.c:402
       do_insert_tree+0x768/0xc38 fs/quota/quota_tree.c:402
       dq_insert_tree fs/quota/quota_tree.c:432 [inline]
       qtree_write_dquot+0x3bc/0x4c8 fs/quota/quota_tree.c:451
       v2_write_dquot+0xf0/0x180 fs/quota/quota_v2.c:361
       dquot_acquire+0x2a8/0x4e0 fs/quota/dquot.c:472
       ext4_acquire_dquot+0x270/0x428 fs/ext4/super.c:6810
       dqget+0x654/0xccc fs/quota/dquot.c:988
       __dquot_initialize+0x264/0xa80 fs/quota/dquot.c:1517
       add_dquot_ref+0x298/0x360 fs/quota/dquot.c:1060
       dquot_load_quota_sb+0x7c4/0xa24 fs/quota/dquot.c:2482
       dquot_load_quota_inode+0x274/0x4e4 fs/quota/dquot.c:2507
       ext4_quota_enable fs/ext4/super.c:7032 [inline]
       ext4_enable_quotas+0x3c4/0xa4c fs/ext4/super.c:7058
       __ext4_remount fs/ext4/super.c:6590 [inline]
       ext4_reconfigure+0x1734/0x2268 fs/ext4/super.c:6671
       reconfigure_super+0x1d4/0x79c fs/super.c:977
       vfs_fsconfig_locked+0x164/0x374 fs/fsopen.c:254
       __do_sys_fsconfig fs/fsopen.c:439 [inline]
       __se_sys_fsconfig fs/fsopen.c:314 [inline]
       __arm64_sys_fsconfig+0x634/0x77c fs/fsopen.c:314
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #1 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       down_read+0x64/0x304 kernel/locking/rwsem.c:1520
       v2_read_dquot+0x4c/0x118 fs/quota/quota_v2.c:335
       dquot_acquire+0x120/0x4e0 fs/quota/dquot.c:463
       ext4_acquire_dquot+0x270/0x428 fs/ext4/super.c:6810
       dqget+0x654/0xccc fs/quota/dquot.c:988
       __dquot_initialize+0x264/0xa80 fs/quota/dquot.c:1517
       add_dquot_ref+0x298/0x360 fs/quota/dquot.c:1060
       dquot_load_quota_sb+0x7c4/0xa24 fs/quota/dquot.c:2482
       dquot_load_quota_inode+0x274/0x4e4 fs/quota/dquot.c:2507
       ext4_quota_enable fs/ext4/super.c:7032 [inline]
       ext4_enable_quotas+0x3c4/0xa4c fs/ext4/super.c:7058
       __ext4_remount fs/ext4/super.c:6590 [inline]
       ext4_reconfigure+0x1734/0x2268 fs/ext4/super.c:6671
       reconfigure_super+0x1d4/0x79c fs/super.c:977
       vfs_fsconfig_locked+0x164/0x374 fs/fsopen.c:254
       __do_sys_fsconfig fs/fsopen.c:439 [inline]
       __se_sys_fsconfig fs/fsopen.c:314 [inline]
       __arm64_sys_fsconfig+0x634/0x77c fs/fsopen.c:314
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (&dquot->dq_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x293c/0x6544 kernel/locking/lockdep.c:5049
       lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
       __mutex_lock_common+0x190/0x1f38 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       dquot_commit+0x50/0x1c4 fs/quota/dquot.c:507
       ext4_write_dquot+0x1b4/0x31c fs/ext4/super.c:6790
       ext4_mark_dquot_dirty+0xe8/0x140 fs/ext4/super.c:6867
       mark_dquot_dirty fs/quota/dquot.c:372 [inline]
       mark_all_dquot_dirty+0x108/0x424 fs/quota/dquot.c:412
       __dquot_alloc_space+0x560/0xce8 fs/quota/dquot.c:1752
       dquot_alloc_space_nodirty include/linux/quotaops.h:300 [inline]
       dquot_alloc_space include/linux/quotaops.h:313 [inline]
       dquot_alloc_block include/linux/quotaops.h:337 [inline]
       ext4_mb_new_blocks+0xd30/0x435c fs/ext4/mballoc.c:5727
       ext4_ext_map_blocks+0x1018/0x559c fs/ext4/extents.c:4340
       ext4_map_blocks+0x860/0x1770 fs/ext4/inode.c:679
       _ext4_get_block+0x194/0x4c8 fs/ext4/inode.c:822
       ext4_get_block+0x4c/0x60 fs/ext4/inode.c:839
       ext4_block_write_begin+0x508/0x10f8 fs/ext4/inode.c:1124
       ext4_write_begin+0x5ec/0x133c fs/ext4/ext4_jbd2.h:-1
       ext4_da_write_begin+0x360/0x9d8 fs/ext4/inode.c:3000
       generic_perform_write+0x230/0x4b0 mm/filemap.c:3846
       ext4_buffered_write_iter+0x2c4/0x530 fs/ext4/file.c:285
       ext4_file_write_iter+0x188/0x152c fs/ext4/file.c:-1
       call_write_iter include/linux/fs.h:2265 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x5ac/0x7c4 fs/read_write.c:584
       ksys_write+0x120/0x210 fs/read_write.c:637
       __do_sys_write fs/read_write.c:649 [inline]
       __se_sys_write fs/read_write.c:646 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

other info that might help us debug this:

Chain exists of:
  &dquot->dq_lock --> &s->s_dquot.dqio_sem --> &ei->i_data_sem/2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->i_data_sem/2);
                               lock(&s->s_dquot.dqio_sem);
                               lock(&ei->i_data_sem/2);
  lock(&dquot->dq_lock);

 *** DEADLOCK ***

5 locks held by syz.1.668/6713:
 #0: ffff0000d9de19e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x114/0x16c fs/file.c:1040
 #1: ffff0000db5f0460 (sb_writers#3){.+.+}-{0:0}, at: vfs_write+0x23c/0x7c4 fs/read_write.c:580
 #2: ffff0000dfd7f258 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #2: ffff0000dfd7f258 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_buffered_write_iter+0x98/0x530 fs/ext4/file.c:279
 #3: ffff0000dfd7f0e0 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_map_blocks+0x7c4/0x1770 fs/ext4/inode.c:672
 #4: ffff80001538d648 (dquot_srcu){....}-{0:0}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:349

stack backtrace:
CPU: 0 PID: 6713 Comm: syz.1.668 Not tainted 6.1.142-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x293c/0x6544 kernel/locking/lockdep.c:5049
 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
 __mutex_lock_common+0x190/0x1f38 kernel/locking/mutex.c:603
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
 dquot_commit+0x50/0x1c4 fs/quota/dquot.c:507
 ext4_write_dquot+0x1b4/0x31c fs/ext4/super.c:6790
 ext4_mark_dquot_dirty+0xe8/0x140 fs/ext4/super.c:6867
 mark_dquot_dirty fs/quota/dquot.c:372 [inline]
 mark_all_dquot_dirty+0x108/0x424 fs/quota/dquot.c:412
 __dquot_alloc_space+0x560/0xce8 fs/quota/dquot.c:1752
 dquot_alloc_space_nodirty include/linux/quotaops.h:300 [inline]
 dquot_alloc_space include/linux/quotaops.h:313 [inline]
 dquot_alloc_block include/linux/quotaops.h:337 [inline]
 ext4_mb_new_blocks+0xd30/0x435c fs/ext4/mballoc.c:5727
 ext4_ext_map_blocks+0x1018/0x559c fs/ext4/extents.c:4340
 ext4_map_blocks+0x860/0x1770 fs/ext4/inode.c:679
 _ext4_get_block+0x194/0x4c8 fs/ext4/inode.c:822
 ext4_get_block+0x4c/0x60 fs/ext4/inode.c:839
 ext4_block_write_begin+0x508/0x10f8 fs/ext4/inode.c:1124
 ext4_write_begin+0x5ec/0x133c fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x360/0x9d8 fs/ext4/inode.c:3000
 generic_perform_write+0x230/0x4b0 mm/filemap.c:3846
 ext4_buffered_write_iter+0x2c4/0x530 fs/ext4/file.c:285
 ext4_file_write_iter+0x188/0x152c fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ac/0x7c4 fs/read_write.c:584
 ksys_write+0x120/0x210 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585