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BUG: KCSAN: data-race in __dentry_kill / d_alloc_parallel

write to 0xffff8881848b1000 of 4 bytes by task 26298 on cpu 1:
 d_alloc_parallel+0x9d7/0xba0 fs/dcache.c:2666
 lookup_open fs/namei.c:3139 [inline]
 open_last_lookups fs/namei.c:3285 [inline]
 path_openat+0x659/0x20b0 fs/namei.c:3491
 do_filp_open+0xd9/0x1f0 fs/namei.c:3521
 do_sys_openat2+0xa3/0x250 fs/open.c:1187
 do_sys_open fs/open.c:1203 [inline]
 __do_sys_open fs/open.c:1211 [inline]
 __se_sys_open fs/open.c:1207 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1207
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881848b1000 of 4 bytes by task 26323 on cpu 0:
 dentry_unlist fs/dcache.c:547 [inline]
 __dentry_kill+0x1ef/0x4e0 fs/dcache.c:578
 dentry_kill fs/dcache.c:695 [inline]
 dput+0xc6/0x360 fs/dcache.c:888
 handle_mounts fs/namei.c:1474 [inline]
 step_into+0x442/0xec0 fs/namei.c:1772
 open_last_lookups fs/namei.c:3308 [inline]
 path_openat+0xfc8/0x20b0 fs/namei.c:3491
 do_filp_open+0xd9/0x1f0 fs/namei.c:3521
 do_sys_openat2+0xa3/0x250 fs/open.c:1187
 do_sys_open fs/open.c:1203 [inline]
 __do_sys_open fs/open.c:1211 [inline]
 __se_sys_open fs/open.c:1207 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1207
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26323 Comm: systemd-udevd Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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