==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / iput

write to 0xffff88810be1f6f8 of 8 bytes by task 8113 on cpu 1:
 __mark_inode_dirty+0x212/0x740 fs/fs-writeback.c:2290
 generic_update_time fs/inode.c:1764 [inline]
 update_time fs/inode.c:1777 [inline]
 file_update_time+0x3b0/0x3f0 fs/inode.c:1992
 file_modified+0x62/0x80 fs/inode.c:2015
 ext4_write_checks fs/ext4/file.c:248 [inline]
 ext4_buffered_write_iter+0x1f9/0x3d0 fs/ext4/file.c:265
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1887 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x617/0x690 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810be1f6f8 of 8 bytes by task 8472 on cpu 0:
 iput+0x2e/0x510 fs/inode.c:1670
 wait_sb_inodes fs/fs-writeback.c:2444 [inline]
 sync_inodes_sb+0x3bf/0x450 fs/fs-writeback.c:2562
 __sync_filesystem fs/sync.c:34 [inline]
 sync_filesystem+0xe4/0x160 fs/sync.c:67
 ovl_sync_fs+0x94/0xc0 fs/overlayfs/super.c:283
 __sync_filesystem fs/sync.c:39 [inline]
 sync_filesystem+0x112/0x160 fs/sync.c:67
 generic_shutdown_super+0x3c/0x1f0 fs/super.c:448
 kill_anon_super+0x23/0x40 fs/super.c:1108
 deactivate_locked_super+0x6a/0xb0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x277/0x2e0 fs/namespace.c:1118
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1125
 task_work_run+0x8e/0x110 kernel/task_work.c:151
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
 exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8472 Comm: syz-executor.1 Not tainted 5.10.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================