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BUG: KCSAN: data-race in __d_rehash / fast_dput

write to 0xffff8881496e9790 of 8 bytes by task 15097 on cpu 1:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
 __d_rehash+0xc4/0x220 fs/dcache.c:2403
 __d_add+0x36d/0x4a0 fs/dcache.c:2618
 d_splice_alias+0xd6/0x270 fs/dcache.c:3009
 ext4_lookup+0x199/0x390 fs/ext4/namei.c:1883
 lookup_one_qstr_excl+0xc0/0x180 fs/namei.c:1608
 filename_create+0x14d/0x2b0 fs/namei.c:3892
 do_symlinkat+0x84/0x340 fs/namei.c:4499
 __do_sys_symlinkat fs/namei.c:4522 [inline]
 __se_sys_symlinkat fs/namei.c:4519 [inline]
 __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4519
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881496e9790 of 8 bytes by task 2773 on cpu 0:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:341 [inline]
 retain_dentry fs/dcache.c:686 [inline]
 fast_dput+0xcf/0x2b0 fs/dcache.c:799
 dput+0x24/0xc0 fs/dcache.c:839
 do_unlinkat+0x257/0x4c0 fs/namei.c:4401
 __do_sys_unlink fs/namei.c:4446 [inline]
 __se_sys_unlink fs/namei.c:4444 [inline]
 __x64_sys_unlink+0x30/0x40 fs/namei.c:4444
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff888237431480 -> 0xffff888153601248

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2773 Comm: udevd Tainted: G        W          6.8.0-rc5-syzkaller-00297-gf2e367d6ad3b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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