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BUG: KCSAN: data-race in d_set_mounted / dput

write to 0xffff888125a493c0 of 4 bytes by task 25024 on cpu 1:
 d_set_mounted+0x193/0x1c0 fs/dcache.c:1438
 get_mountpoint+0x13d/0x2d0 fs/namespace.c:724
 lock_mount+0xa0/0x1a0 fs/namespace.c:2142
 do_add_mount+0x30/0x1e0 fs/namespace.c:2706
 do_new_mount_fc fs/namespace.c:2767 [inline]
 do_new_mount fs/namespace.c:2825 [inline]
 do_mount+0x12e7/0x1560 fs/namespace.c:3143
 ksys_mount+0xe8/0x160 fs/namespace.c:3352
 __do_sys_mount fs/namespace.c:3366 [inline]
 __se_sys_mount fs/namespace.c:3363 [inline]
 __x64_sys_mount+0x70/0x90 fs/namespace.c:3363
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888125a493c0 of 4 bytes by task 25022 on cpu 0:
 fast_dput fs/dcache.c:727 [inline]
 dput+0x4d/0x750 fs/dcache.c:846
 path_to_nameidata fs/namei.c:830 [inline]
 do_last fs/namei.c:3337 [inline]
 path_openat+0x29aa/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 ksys_open include/linux/syscalls.h:1385 [inline]
 __do_sys_creat fs/open.c:1155 [inline]
 __se_sys_creat fs/open.c:1153 [inline]
 __x64_sys_creat+0x45/0x60 fs/open.c:1153
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25022 Comm: syz-executor.0 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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