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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

write to 0xffff8881211366c0 of 4 bytes by task 29311 on cpu 0:
 d_set_d_op+0x10f/0x220 fs/dcache.c:1906
 proc_lookup_de+0x1da/0x230 fs/proc/generic.c:257
 proc_tgid_net_lookup+0x3f/0xc0 fs/proc/proc_net.c:286
 lookup_open fs/namei.c:3193 [inline]
 open_last_lookups fs/namei.c:3285 [inline]
 path_openat+0xb5a/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_openat fs/open.c:1219 [inline]
 __se_sys_openat fs/open.c:1214 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1214
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881211366c0 of 4 bytes by task 29309 on cpu 1:
 d_in_lookup include/linux/dcache.h:366 [inline]
 d_wait_lookup fs/dcache.c:2556 [inline]
 d_alloc_parallel+0x4ff/0xba0 fs/dcache.c:2644
 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_openat fs/open.c:1219 [inline]
 __se_sys_openat fs/open.c:1214 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1214
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29309 Comm: syz-executor.5 Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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