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BUG: KCSAN: data-race in fprop_new_period / fprop_reflect_period_percpu

read-write to 0xffffffff86efbd60 of 4 bytes by interrupt on cpu 1:
 fprop_new_period+0xaa/0xe0 lib/flex_proportions.c:79
 writeout_period+0x59/0xe0 mm/page-writeback.c:613
 call_timer_fn+0x37/0x2f0 kernel/time/timer.c:1700
 expire_timers kernel/time/timer.c:1751 [inline]
 __run_timers+0x46c/0x650 kernel/time/timer.c:2022
 run_timer_softirq+0x31/0x40 kernel/time/timer.c:2037
 __do_softirq+0xc4/0x279 kernel/softirq.c:553
 invoke_softirq kernel/softirq.c:427 [inline]
 __irq_exit_rcu kernel/softirq.c:632 [inline]
 irq_exit_rcu+0x3b/0x90 kernel/softirq.c:644
 sysvec_apic_timer_interrupt+0x6d/0x80 arch/x86/kernel/apic/apic.c:1076
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
 kcsan_setup_watchpoint+0x3fe/0x410 kernel/kcsan/core.c:705
 node_tag_set lib/radix-tree.c:946 [inline]
 __radix_tree_delete+0x193/0x580 lib/radix-tree.c:1373
 radix_tree_delete_item+0x195/0x260 lib/radix-tree.c:1430
 idr_remove+0x2e/0x40 lib/idr.c:154
 kernfs_put+0x191/0x2a0 fs/kernfs/dir.c:567
 kernfs_remove_by_name_ns+0x91/0xe0 fs/kernfs/dir.c:1674
 kernfs_remove_by_name include/linux/kernfs.h:623 [inline]
 remove_files fs/sysfs/group.c:28 [inline]
 sysfs_remove_group+0x95/0x190 fs/sysfs/group.c:292
 sysfs_remove_groups+0x3a/0x80 fs/sysfs/group.c:316
 device_remove_groups drivers/base/core.c:2734 [inline]
 device_remove_attrs+0x10d/0x190 drivers/base/core.c:2909
 device_del+0x35b/0x7a0 drivers/base/core.c:3813
 netdev_unregister_kobject+0x115/0x120 net/core/net-sysfs.c:2016
 unregister_netdevice_many_notify+0xc3e/0x1080 net/core/dev.c:11013
 unregister_netdevice_many+0x19/0x20 net/core/dev.c:11039
 ip_tunnel_delete_nets+0x208/0x240 net/ipv4/ip_tunnel.c:1144
 erspan_exit_batch_net+0x2e/0x30 net/ipv4/ip_gre.c:1717
 ops_exit_list net/core/net_namespace.c:175 [inline]
 setup_net+0x55f/0x710 net/core/net_namespace.c:362
 copy_net_ns+0x384/0x520 net/core/net_namespace.c:491
 create_new_namespaces+0x228/0x430 kernel/nsproxy.c:110
 copy_namespaces+0x1a9/0x200 kernel/nsproxy.c:179
 copy_process+0x1029/0x20a0 kernel/fork.c:2505
 kernel_clone+0x169/0x560 kernel/fork.c:2907
 __do_sys_clone kernel/fork.c:3050 [inline]
 __se_sys_clone kernel/fork.c:3034 [inline]
 __x64_sys_clone+0xe8/0x120 kernel/fork.c:3034
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffffffff86efbd60 of 4 bytes by task 6978 on cpu 0:
 fprop_reflect_period_percpu+0x22/0x1a0 lib/flex_proportions.c:188
 __fprop_add_percpu lib/flex_proportions.c:219 [inline]
 __fprop_add_percpu_max+0x58/0x180 lib/flex_proportions.c:277
 wb_domain_writeout_add mm/page-writeback.c:560 [inline]
 __wb_writeout_add+0x7e/0x1d0 mm/page-writeback.c:584
 __folio_end_writeback+0x21b/0x4a0 mm/page-writeback.c:2963
 folio_end_writeback+0x74/0x1f0 mm/filemap.c:1598
 ext4_finish_bio+0x45c/0x8c0 fs/ext4/page-io.c:145
 ext4_release_io_end+0x8c/0x1e0 fs/ext4/page-io.c:160
 ext4_end_io_end fs/ext4/page-io.c:194 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:259 [inline]
 ext4_end_io_rsv_work+0x2d3/0x360 fs/ext4/page-io.c:273
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

value changed: 0x0000011f -> 0x00000120

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6978 Comm: kworker/u4:17 Not tainted 6.6.0-syzkaller-14614-g77fa2fbe87fc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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