==================================================================
BUG: KCSAN: data-race in __generic_file_fsync / writeback_sb_inodes

write to 0xffff888119c8b728 of 4 bytes by task 51 on cpu 1:
 writeback_sb_inodes+0x33d/0xa30 fs/fs-writeback.c:2004
 __writeback_inodes_wb+0x94/0x1a0 fs/fs-writeback.c:2086
 wb_writeback+0x266/0x5c0 fs/fs-writeback.c:2197
 wb_check_start_all fs/fs-writeback.c:2323 [inline]
 wb_do_writeback fs/fs-writeback.c:2349 [inline]
 wb_workfn+0x4c9/0x910 fs/fs-writeback.c:2382
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888119c8b728 of 4 bytes by task 5187 on cpu 0:
 __generic_file_fsync+0x94/0x140 fs/libfs.c:1545
 fat_file_fsync+0x49/0x100 fs/fat/file.c:191
 vfs_fsync_range+0x10d/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3036 [inline]
 generic_file_write_iter+0x1b8/0x2f0 mm/filemap.c:4322
 iter_file_splice_write+0x663/0xa60 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00020070 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5187 Comm: syz.2.636 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================