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BUG: KCSAN: data-race in d_make_discardable / step_into_slowpath

write to 0xffff88811a873000 of 4 bytes by task 4597 on cpu 0:
 d_make_discardable+0x4f/0x90 fs/dcache.c:1050
 simple_unlink+0x68/0x80 fs/libfs.c:808
 shmem_unlink+0x12d/0x140 mm/shmem.c:3917
 shmem_rename2+0x185/0x310 mm/shmem.c:3998
 vfs_rename+0x963/0xac0 fs/namei.c:6070
 filename_renameat2+0x3a4/0x6a0 fs/namei.c:6188
 __do_sys_rename fs/namei.c:6232 [inline]
 __se_sys_rename+0x4a/0x1c0 fs/namei.c:6228
 __x64_sys_rename+0x31/0x40 fs/namei.c:6228
 x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a873000 of 4 bytes by task 3285 on cpu 1:
 d_managed include/linux/dcache.h:433 [inline]
 handle_mounts fs/namei.c:1738 [inline]
 step_into_slowpath+0xea/0x4c0 fs/namei.c:2104
 step_into fs/namei.c:2152 [inline]
 walk_component fs/namei.c:2288 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x2eb/0x4c0 fs/namei.c:2813
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 vfs_statx+0x96/0x170 fs/stat.c:353
 vfs_fstatat+0x118/0x170 fs/stat.c:373
 __do_sys_newfstatat fs/stat.c:538 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
 x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08300080 -> 0x00004180

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3285 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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