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BUG: KCSAN: data-race in __dentry_kill / d_alloc_parallel

read to 0xffff8881257ac840 of 4 bytes by task 8448 on cpu 1:
 dentry_unlist fs/dcache.c:544 [inline]
 __dentry_kill+0x1be/0x3c0 fs/dcache.c:575
 dentry_kill fs/dcache.c:698 [inline]
 dput+0x3b5/0x750 fs/dcache.c:859
 path_put_conditional fs/namei.c:821 [inline]
 follow_managed+0x1eb/0x6f0 fs/namei.c:1279
 walk_component+0x4ec/0xd90 fs/namei.c:1808
 lookup_last fs/namei.c:2260 [inline]
 path_lookupat.isra.0+0x13a/0x5a0 fs/namei.c:2305
 filename_lookup+0x145/0x2b0 fs/namei.c:2335
 user_path_at_empty+0x4c/0x70 fs/namei.c:2615
 do_readlinkat+0x84/0x220 fs/stat.c:399
 __do_sys_readlink fs/stat.c:432 [inline]
 __se_sys_readlink fs/stat.c:429 [inline]
 __x64_sys_readlink+0x51/0x70 fs/stat.c:429
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881257ac840 of 4 bytes by task 19695 on cpu 0:
 d_alloc_parallel+0x533/0xe00 fs/dcache.c:2612
 __lookup_slow+0xb4/0x2a0 fs/namei.c:1648
 lookup_slow+0x4f/0x70 fs/namei.c:1682
 walk_component+0x490/0xd90 fs/namei.c:1802
 lookup_last fs/namei.c:2260 [inline]
 path_lookupat.isra.0+0x13a/0x5a0 fs/namei.c:2305
 filename_lookup+0x145/0x2b0 fs/namei.c:2335
 user_path_at_empty+0x4c/0x70 fs/namei.c:2615
 do_readlinkat+0x84/0x220 fs/stat.c:399
 __do_sys_readlink fs/stat.c:432 [inline]
 __se_sys_readlink fs/stat.c:429 [inline]
 __x64_sys_readlink+0x51/0x70 fs/stat.c:429
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19695 Comm: udevd Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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