loop4: detected capacity change from 0 to 128
FAT-fs (loop4): Invalid FSINFO signature: 0x00615252, 0x61417272 (sector = 1)
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BUG: KCSAN: data-race in __mark_inode_dirty / __writeback_single_inode

read-write to 0xffff8881067f1028 of 4 bytes by task 31 on cpu 1:
 __writeback_single_inode+0x1f4/0x850 fs/fs-writeback.c:1716
 writeback_sb_inodes+0x458/0xa10 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0x9a/0x1a0 fs/fs-writeback.c:2047
 wb_writeback+0x276/0x650 fs/fs-writeback.c:2158
 wb_check_start_all fs/fs-writeback.c:2284 [inline]
 wb_do_writeback fs/fs-writeback.c:2310 [inline]
 wb_workfn+0x510/0x960 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881067f1028 of 4 bytes by task 15523 on cpu 0:
 __mark_inode_dirty+0x58/0x7e0 fs/fs-writeback.c:2509
 mark_inode_dirty include/linux/fs.h:2545 [inline]
 generic_write_end+0x137/0x160 fs/buffer.c:2306
 fat_write_end+0x4e/0x160 fs/fat/inode.c:242
 generic_perform_write+0x31e/0x4b0 mm/filemap.c:4123
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4219
 generic_file_write_iter+0x92/0x310 mm/filemap.c:4245
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x79b/0x950 fs/read_write.c:684
 ksys_write+0xeb/0x1b0 fs/read_write.c:736
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:744
 x64_sys_call+0x2a45/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0001003a -> 0x00010020

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 15523 Comm: syz.4.4368 Not tainted 6.14.0-syzkaller-13524-gf4d2ef48250a #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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