syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.9.2185/15677 is trying to acquire lock:
ffff888054f66610 (sb_internal){.+.+}-{0:0}, at: percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
ffff888054f66610 (sb_internal){.+.+}-{0:0}, at: __sb_start_write include/linux/fs/super.h:19 [inline]
ffff888054f66610 (sb_internal){.+.+}-{0:0}, at: sb_start_intwrite include/linux/fs/super.h:177 [inline]
ffff888054f66610 (sb_internal){.+.+}-{0:0}, at: ext4_evict_inode+0x26f/0xe60 fs/ext4/inode.c:214

but task is already holding lock:
ffff8880790a0b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1832 [inline]
ffff8880790a0b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2f3/0x1010 fs/ext4/migrate.c:438

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->s_writepages_rwsem){++++}-{0:0}:
       percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       ext4_writepages_down_read fs/ext4/ext4.h:1820 [inline]
       ext4_writepages+0x1ca/0x350 fs/ext4/inode.c:3025
       do_writepages+0x32e/0x550 mm/page-writeback.c:2598
       __writeback_single_inode+0x133/0x1240 fs/fs-writeback.c:1737
       writeback_single_inode+0x493/0xc70 fs/fs-writeback.c:1858
       write_inode_now+0x160/0x1d0 fs/fs-writeback.c:2924
       iput_final fs/inode.c:1941 [inline]
       iput+0xa77/0x1030 fs/inode.c:2003
       ext4_xattr_block_set+0x1fce/0x2ac0 fs/ext4/xattr.c:2203
       ext4_xattr_move_to_block fs/ext4/xattr.c:2668 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2743 [inline]
       ext4_expand_extra_isize_ea+0x12da/0x1ea0 fs/ext4/xattr.c:2831
       __ext4_expand_extra_isize+0x30d/0x400 fs/ext4/inode.c:6349
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6392 [inline]
       __ext4_mark_inode_dirty+0x45c/0x6e0 fs/ext4/inode.c:6470
       ext4_evict_inode+0x79c/0xe60 fs/ext4/inode.c:253
       evict+0x5f4/0xae0 fs/inode.c:837
       ext4_orphan_cleanup+0xc20/0x1460 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5658 [inline]
       ext4_fill_super+0x58a1/0x6160 fs/ext4/super.c:5777
       get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
       vfs_get_tree+0x92/0x2a0 fs/super.c:1751
       fc_mount fs/namespace.c:1199 [inline]
       do_new_mount_fc fs/namespace.c:3636 [inline]
       do_new_mount+0x302/0xa10 fs/namespace.c:3712
       do_mount fs/namespace.c:4035 [inline]
       __do_sys_mount fs/namespace.c:4224 [inline]
       __se_sys_mount+0x313/0x410 fs/namespace.c:4201
       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 (sb_internal){.+.+}-{0:0}:
       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
       percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs/super.h:19 [inline]
       sb_start_intwrite include/linux/fs/super.h:177 [inline]
       ext4_evict_inode+0x26f/0xe60 fs/ext4/inode.c:214
       evict+0x5f4/0xae0 fs/inode.c:837
       ext4_ext_migrate+0xd23/0x1010 fs/ext4/migrate.c:588
       __ext4_ioctl fs/ext4/ioctl.c:1688 [inline]
       ext4_ioctl+0x204a/0x4760 fs/ext4/ioctl.c:1917
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->s_writepages_rwsem);
                               lock(sb_internal);
                               lock(&sbi->s_writepages_rwsem);
  rlock(sb_internal);

 *** DEADLOCK ***

3 locks held by syz.9.2185/15677:
 #0: ffff888054f66420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x60/0x200 fs/namespace.c:543
 #1: ffff888051873400 (&sb->s_type->i_mutex_key#11){++++}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
 #1: ffff888051873400 (&sb->s_type->i_mutex_key#11){++++}-{4:4}, at: __ext4_ioctl fs/ext4/ioctl.c:1687 [inline]
 #1: ffff888051873400 (&sb->s_type->i_mutex_key#11){++++}-{4:4}, at: ext4_ioctl+0x2042/0x4760 fs/ext4/ioctl.c:1917
 #2: ffff8880790a0b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1832 [inline]
 #2: ffff8880790a0b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2f3/0x1010 fs/ext4/migrate.c:438

stack backtrace:
CPU: 0 UID: 0 PID: 15677 Comm: syz.9.2185 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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
 percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_intwrite include/linux/fs/super.h:177 [inline]
 ext4_evict_inode+0x26f/0xe60 fs/ext4/inode.c:214
 evict+0x5f4/0xae0 fs/inode.c:837
 ext4_ext_migrate+0xd23/0x1010 fs/ext4/migrate.c:588
 __ext4_ioctl fs/ext4/ioctl.c:1688 [inline]
 ext4_ioctl+0x204a/0x4760 fs/ext4/ioctl.c:1917
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 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
RIP: 0033:0x7f3ced38f749
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:00007f3ceb5f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f3ced5e6090 RCX: 00007f3ced38f749
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000005
RBP: 00007f3ced413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3ced5e6128 R14: 00007f3ced5e6090 R15: 00007ffcd58a49c8
 </TASK>