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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888149b7be40 of 4 bytes by task 8611 on cpu 0:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2011
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:2055
 ext4_mkdir+0x5e5/0x740 fs/ext4/namei.c:3046
 vfs_mkdir+0x1ac/0x2b0 fs/namei.c:4117
 do_mkdirat+0xf9/0x260 fs/namei.c:4140
 __do_sys_mkdirat fs/namei.c:4155 [inline]
 __se_sys_mkdirat fs/namei.c:4153 [inline]
 __x64_sys_mkdirat+0x50/0x60 fs/namei.c:4153
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888149b7be40 of 4 bytes by task 8612 on cpu 1:
 d_revalidate fs/namei.c:858 [inline]
 lookup_fast+0xd9/0x290 fs/namei.c:1639
 walk_component+0x3f/0x230 fs/namei.c:1994
 lookup_last fs/namei.c:2455 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2479
 filename_lookup+0x126/0x300 fs/namei.c:2508
 user_path_at_empty+0x42/0x110 fs/namei.c:2907
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3672 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount+0x24b/0x2d0 fs/namespace.c:3861
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0x00280000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8612 Comm: syz-executor.5 Not tainted 6.5.0-rc4-syzkaller-00245-gf6a691685962 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
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