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BUG: KCSAN: data-race in __d_instantiate / step_into

write to 0xffff88811a0eddb0 of 8 bytes by task 12743 on cpu 1:
 __d_set_inode_and_type fs/dcache.c:406 [inline]
 __d_instantiate+0x1f8/0x3b0 fs/dcache.c:1936
 d_instantiate+0x59/0x80 fs/dcache.c:1963
 shmem_mknod+0x153/0x180 mm/shmem.c:3866
 shmem_mkdir+0x33/0x70 mm/shmem.c:3909
 vfs_mkdir+0x213/0x340 fs/namei.c:4453
 do_mkdirat+0x132/0x3f0 fs/namei.c:4486
 __do_sys_mkdirat fs/namei.c:4503 [inline]
 __se_sys_mkdirat fs/namei.c:4501 [inline]
 __x64_sys_mkdirat+0x4c/0x60 fs/namei.c:4501
 x64_sys_call+0x2b7/0x3000 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a0eddb0 of 8 bytes by task 12741 on cpu 0:
 step_into+0x122/0x7f0 fs/namei.c:1993
 walk_component+0x162/0x220 fs/namei.c:2157
 lookup_last fs/namei.c:2652 [inline]
 path_lookupat+0xfe/0x2a0 fs/namei.c:2676
 filename_lookup+0x147/0x340 fs/namei.c:2705
 user_path_at+0x3e/0x130 fs/namei.c:3215
 do_mount fs/namespace.c:4038 [inline]
 __do_sys_mount fs/namespace.c:4229 [inline]
 __se_sys_mount+0x25b/0x2e0 fs/namespace.c:4206
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4206
 x64_sys_call+0x2b51/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff888119f85aa8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 12741 Comm: syz.3.3265 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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