syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.7121/27485 is trying to acquire lock:
ffff888073490650 (sb_internal){++++}-{0:0}, at: __sb_start_write include/linux/fs.h:1891 [inline]
ffff888073490650 (sb_internal){++++}-{0:0}, at: sb_start_intwrite include/linux/fs.h:2013 [inline]
ffff888073490650 (sb_internal){++++}-{0:0}, at: ext4_evict_inode+0x43c/0x1110 fs/ext4/inode.c:240

but task is already holding lock:
ffff888078b84b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 fs/ext4/migrate.c:437

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+0x44/0x1a0 include/linux/percpu-rwsem.h:51
       ext4_writepages+0x20f/0x2f40 fs/ext4/inode.c:2715
       do_writepages+0x3ba/0x640 mm/page-writeback.c:2491
       __writeback_single_inode+0x156/0x1160 fs/fs-writeback.c:1622
       writeback_single_inode+0x3cb/0x8e0 fs/fs-writeback.c:1743
       write_inode_now+0x17f/0x210 fs/fs-writeback.c:2780
       iput_final fs/inode.c:1821 [inline]
       iput+0x613/0x980 fs/inode.c:1860
       ext4_xattr_block_set+0x273b/0x32b0 fs/ext4/xattr.c:2145
       ext4_xattr_move_to_block fs/ext4/xattr.c:2610 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2685 [inline]
       ext4_expand_extra_isize_ea+0x120b/0x1dc0 fs/ext4/xattr.c:2773
       __ext4_expand_extra_isize+0x301/0x3e0 fs/ext4/inode.c:5984
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6027 [inline]
       __ext4_mark_inode_dirty+0x47f/0x770 fs/ext4/inode.c:6105
       ext4_evict_inode+0xa7f/0x1110 fs/ext4/inode.c:279
       evict+0x4c9/0x8d0 fs/inode.c:705
       ext4_orphan_cleanup+0xbeb/0x1420 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5556 [inline]
       ext4_fill_super+0x7829/0x7dc0 fs/ext4/super.c:5687
       get_tree_bdev+0x3f1/0x610 fs/super.c:1366
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x24a/0xa40 fs/namespace.c:3078
       do_mount fs/namespace.c:3421 [inline]
       __do_sys_mount fs/namespace.c:3629 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (sb_internal){++++}-{0:0}:
       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+0x2d07/0x7d10 kernel/locking/lockdep.c:5049
       lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
       percpu_down_read+0x44/0x1a0 include/linux/percpu-rwsem.h:51
       __sb_start_write include/linux/fs.h:1891 [inline]
       sb_start_intwrite include/linux/fs.h:2013 [inline]
       ext4_evict_inode+0x43c/0x1110 fs/ext4/inode.c:240
       evict+0x4c9/0x8d0 fs/inode.c:705
       ext4_ext_migrate+0xc0c/0xe60 fs/ext4/migrate.c:587
       __ext4_ioctl fs/ext4/ioctl.c:1396 [inline]
       ext4_ioctl+0x1eb1/0x4110 fs/ext4/ioctl.c:1614
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

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);
  lock(sb_internal);

 *** DEADLOCK ***

3 locks held by syz.8.7121/27485:
 #0: ffff888073490460 (sb_writers#4){++++}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:446
 #1: ffff88803bc9d440 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff88803bc9d440 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1395 [inline]
 #1: ffff88803bc9d440 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_ioctl+0x1ea9/0x4110 fs/ext4/ioctl.c:1614
 #2: ffff888078b84b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 fs/ext4/migrate.c:437

stack backtrace:
CPU: 1 PID: 27485 Comm: syz.8.7121 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x296/0x330 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+0x2d07/0x7d10 kernel/locking/lockdep.c:5049
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 percpu_down_read+0x44/0x1a0 include/linux/percpu-rwsem.h:51
 __sb_start_write include/linux/fs.h:1891 [inline]
 sb_start_intwrite include/linux/fs.h:2013 [inline]
 ext4_evict_inode+0x43c/0x1110 fs/ext4/inode.c:240
 evict+0x4c9/0x8d0 fs/inode.c:705
 ext4_ext_migrate+0xc0c/0xe60 fs/ext4/migrate.c:587
 __ext4_ioctl fs/ext4/ioctl.c:1396 [inline]
 ext4_ioctl+0x1eb1/0x4110 fs/ext4/ioctl.c:1614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8e8b19aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8e8bf9c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8e8b415fa0 RCX: 00007f8e8b19aeb9
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000004
RBP: 00007f8e8b208c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8e8b416038 R14: 00007f8e8b415fa0 R15: 00007fff242df1f8
 </TASK>