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BUG: KCSAN: data-race in __ext4_new_inode / _find_next_zero_bit

read-write to 0xffff888105e2a100 of 8 bytes by task 28004 on cpu 0:
 instrument_read_write include/linux/instrumented.h:55 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:99 [inline]
 __test_and_set_bit_le include/asm-generic/bitops/le.h:56 [inline]
 __ext4_new_inode+0x106f/0x2330 fs/ext4/ialloc.c:1098
 ext4_symlink+0x284/0x660 fs/ext4/namei.c:3386
 vfs_symlink+0x2c3/0x3c0 fs/namei.c:5523
 do_symlinkat+0xf0/0x460 fs/namei.c:5550
 __do_sys_symlinkat fs/namei.c:5571 [inline]
 __se_sys_symlinkat fs/namei.c:5568 [inline]
 __x64_sys_symlinkat+0x5a/0x70 fs/namei.c:5568
 x64_sys_call+0x2a36/0x3000 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105e2a100 of 8 bytes by task 28003 on cpu 1:
 _find_next_zero_bit+0x64/0xa0 lib/find_bit.c:222
 find_next_zero_bit include/linux/find.h:192 [inline]
 find_next_zero_bit_le include/linux/find.h:512 [inline]
 find_inode_bit+0xac/0x320 fs/ext4/ialloc.c:726
 __ext4_new_inode+0xd1e/0x2330 fs/ext4/ialloc.c:1067
 ext4_symlink+0x284/0x660 fs/ext4/namei.c:3386
 vfs_symlink+0x2c3/0x3c0 fs/namei.c:5523
 do_symlinkat+0xf0/0x460 fs/namei.c:5550
 __do_sys_symlinkat fs/namei.c:5571 [inline]
 __se_sys_symlinkat fs/namei.c:5568 [inline]
 __x64_sys_symlinkat+0x5a/0x70 fs/namei.c:5568
 x64_sys_call+0x2a36/0x3000 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 28003 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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