syzbot

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BUG: KCSAN: data-race in __d_lookup_rcu / __d_rehash

read to 0xffff888101befe50 of 8 bytes by task 1442 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:332 [inline]
 __d_lookup_rcu+0x150/0x440 fs/dcache.c:2348
 lookup_fast+0xc1/0x360 fs/namei.c:1630
 walk_component+0x6b/0x280 fs/namei.c:2016
 link_path_walk+0x459/0x7a0
 path_openat+0x199/0x1b30 fs/namei.c:3605
 do_filp_open+0x105/0x220 fs/namei.c:3636
 do_sys_openat2+0xb5/0x2a0 fs/open.c:1213
 do_sys_open fs/open.c:1229 [inline]
 __do_sys_openat fs/open.c:1245 [inline]
 __se_sys_openat fs/open.c:1240 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1240
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff888101befe50 of 8 bytes by task 5303 on cpu 0:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
 __d_rehash+0xb9/0x1f0 fs/dcache.c:2545
 __d_add+0x355/0x470 fs/dcache.c:2739
 d_splice_alias+0xd5/0x310 fs/dcache.c:3126
 ext4_lookup+0x156/0x300 fs/ext4/namei.c:1813
 __lookup_hash+0xbc/0x180 fs/namei.c:1608
 filename_create+0x147/0x2b0 fs/namei.c:3703
 do_symlinkat+0x83/0x330 fs/namei.c:4316
 __do_sys_symlinkat fs/namei.c:4343 [inline]
 __se_sys_symlinkat fs/namei.c:4340 [inline]
 __x64_sys_symlinkat+0x5e/0x70 fs/namei.c:4340
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5303 Comm: syz-executor.4 Not tainted 5.18.0-rc3-syzkaller-00007-g559089e0a93d-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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