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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff8881066c8cc0 of 4 bytes by task 31130 on cpu 0:
 d_set_d_op+0xfb/0x1f0 fs/dcache.c:1792
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2651
 proc_pident_lookup+0x112/0x180 fs/proc/base.c:2674
 proc_tgid_base_lookup+0x2b/0x40 fs/proc/base.c:3386
 __lookup_slow+0x184/0x250 fs/namei.c:1692
 lookup_slow+0x3c/0x60 fs/namei.c:1709
 walk_component fs/namei.c:2004 [inline]
 link_path_walk+0x621/0x810 fs/namei.c:2331
 path_openat+0x1a1/0x1d80 fs/namei.c:3795
 do_filp_open+0xf7/0x200 fs/namei.c:3826
 do_sys_openat2+0xab/0x120 fs/open.c:1406
 do_sys_open fs/open.c:1421 [inline]
 __do_sys_openat fs/open.c:1437 [inline]
 __se_sys_openat fs/open.c:1432 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1432
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

read to 0xffff8881066c8cc0 of 4 bytes by task 31129 on cpu 1:
 d_in_lookup include/linux/dcache.h:371 [inline]
 d_wait_lookup fs/dcache.c:2443 [inline]
 d_alloc_parallel+0x5ff/0xc70 fs/dcache.c:2531
 __lookup_slow+0x8d/0x250 fs/namei.c:1677
 lookup_slow+0x3c/0x60 fs/namei.c:1709
 walk_component fs/namei.c:2004 [inline]
 link_path_walk+0x621/0x810 fs/namei.c:2331
 path_openat+0x1a1/0x1d80 fs/namei.c:3795
 do_filp_open+0xf7/0x200 fs/namei.c:3826
 do_sys_openat2+0xab/0x120 fs/open.c:1406
 do_sys_open fs/open.c:1421 [inline]
 __do_sys_openat fs/open.c:1437 [inline]
 __se_sys_openat fs/open.c:1432 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1432
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 31129 Comm: syz-executor.2 Not tainted 6.8.0-syzkaller-13236-g5e74df2f8f15 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
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