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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff88811b4f0c00 of 4 bytes by task 5328 on cpu 1:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2a8/0x390 fs/dcache.c:2154
 d_make_persistent+0x72/0x110 fs/dcache.c:2978
 shmem_mknod+0x15f/0x170 mm/shmem.c:3851
 shmem_mkdir+0x33/0x70 mm/shmem.c:3893
 vfs_mkdir+0x291/0x3e0 fs/namei.c:5410
 filename_mkdirat+0x138/0x300 fs/namei.c:5443
 __do_sys_mkdir fs/namei.c:5470 [inline]
 __se_sys_mkdir+0x31/0xf0 fs/namei.c:5467
 __x64_sys_mkdir+0x31/0x40 fs/namei.c:5467
 x64_sys_call+0x18da/0x2550 arch/x86/include/generated/asm/syscalls_64.h:84
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b4f0c00 of 4 bytes by task 5333 on cpu 0:
 d_revalidate fs/namei.c:1034 [inline]
 lookup_fast+0xf1/0x320 fs/namei.c:1868
 walk_component fs/namei.c:2278 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x120/0x4c0 fs/namei.c:2813
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 user_path_at+0x3e/0x100 fs/namei.c:3641
 do_mount fs/namespace.c:4178 [inline]
 __do_sys_mount fs/namespace.c:4397 [inline]
 __se_sys_mount+0x25b/0x2e0 fs/namespace.c:4374
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4374
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000080 -> 0x08100080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5333 Comm: syz.4.339 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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