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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff888037646240 of 4 bytes by task 4891 on cpu 0:
 d_set_d_op+0x14c/0x1e0 fs/dcache.c:1875
 simple_lookup+0x78/0x90 fs/libfs.c:73
 lookup_open fs/namei.c:3083 [inline]
 open_last_lookups fs/namei.c:3178 [inline]
 path_openat+0xb8f/0x20a0 fs/namei.c:3366
 do_filp_open+0xbd/0x1d0 fs/namei.c:3396
 do_sys_openat2+0xa3/0x240 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_open fs/open.c:1192 [inline]
 __se_sys_open fs/open.c:1188 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1188
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888037646240 of 4 bytes by task 5160 on cpu 1:
 d_in_lookup include/linux/dcache.h:362 [inline]
 d_wait_lookup fs/dcache.c:2521 [inline]
 d_alloc_parallel+0x60e/0xcc0 fs/dcache.c:2609
 lookup_open fs/namei.c:3031 [inline]
 open_last_lookups fs/namei.c:3178 [inline]
 path_openat+0x682/0x20a0 fs/namei.c:3366
 do_filp_open+0xbd/0x1d0 fs/namei.c:3396
 do_sys_openat2+0xa3/0x240 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_open fs/open.c:1192 [inline]
 __se_sys_open fs/open.c:1188 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1188
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5160 Comm: systemd-udevd Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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