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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff88813f01b600 of 4 bytes by task 15725 on cpu 1:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2010
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:2054
 ext4_mkdir+0x5e5/0x740 fs/ext4/namei.c:3047
 vfs_mkdir+0x1ac/0x2b0 fs/namei.c:4120
 do_mkdirat+0xf9/0x260 fs/namei.c:4143
 __do_sys_mkdirat fs/namei.c:4158 [inline]
 __se_sys_mkdirat fs/namei.c:4156 [inline]
 __x64_sys_mkdirat+0x50/0x60 fs/namei.c:4156
 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 0xffff88813f01b600 of 4 bytes by task 15726 on cpu 0:
 d_revalidate fs/namei.c:860 [inline]
 lookup_fast+0xd9/0x290 fs/namei.c:1642
 walk_component+0x3f/0x230 fs/namei.c:1997
 lookup_last fs/namei.c:2458 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2482
 filename_lookup+0x126/0x300 fs/namei.c:2511
 user_path_at_empty+0x42/0x110 fs/namei.c:2910
 user_path_at include/linux/namei.h:57 [inline]
 __do_sys_chdir fs/open.c:551 [inline]
 __se_sys_chdir+0x4f/0x140 fs/open.c:545
 __x64_sys_chdir+0x1f/0x30 fs/open.c:545
 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: 0 PID: 15726 Comm: syz-executor.5 Not tainted 6.5.0-syzkaller-12728-ga48fa7efaf11 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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