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BUG: KCSAN: data-race in __delayacct_blkio_end / __delayacct_blkio_start

write to 0xffff88810131e418 of 8 bytes by task 14894 on cpu 0:
 __delayacct_blkio_start+0x35/0x40 kernel/delayacct.c:61
 delayacct_blkio_start include/linux/delayacct.h:119 [inline]
 __schedule+0x18c/0x550 kernel/sched/core.c:4485
 schedule+0x7f/0xb0 kernel/sched/core.c:4601
 io_schedule+0x3b/0x50 kernel/sched/core.c:6295
 wait_on_page_bit_common+0x633/0x910 mm/filemap.c:1273
 __lock_page+0x5f/0x70 mm/filemap.c:1531
 lock_page include/linux/pagemap.h:611 [inline]
 mpage_prepare_extent_to_map+0x2bd/0x630 fs/ext4/inode.c:2592
 ext4_writepages+0x674/0x1e30 fs/ext4/inode.c:2746
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 __filemap_fdatawrite mm/filemap.c:430 [inline]
 filemap_flush+0x1f/0x30 mm/filemap.c:457
 ext4_alloc_da_blocks+0x4a/0x100 fs/ext4/inode.c:3156
 ext4_release_file+0x5b/0x1d0 fs/ext4/file.c:142
 __fput+0x243/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:151
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
 exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810131e418 of 8 bytes by task 21 on cpu 1:
 delayacct_end kernel/delayacct.c:48 [inline]
 __delayacct_blkio_end+0x70/0xf0 kernel/delayacct.c:82
 delayacct_blkio_end include/linux/delayacct.h:125 [inline]
 try_to_wake_up+0x107/0x470 kernel/sched/core.c:2892
 wake_page_function+0xd9/0x200 mm/filemap.c:1080
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:93
 wake_up_page_bit+0xa4/0x190 mm/filemap.c:1113
 unlock_page+0x5e/0x70 mm/filemap.c:1465
 ext4_bio_write_page+0xc48/0xda0 fs/ext4/page-io.c:559
 mpage_submit_page fs/ext4/inode.c:2092 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2340 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2479 [inline]
 ext4_writepages+0xe9b/0x1e30 fs/ext4/inode.c:2792
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __writeback_single_inode+0x84/0x560 fs/fs-writeback.c:1461
 writeback_sb_inodes+0x6a0/0x1020 fs/fs-writeback.c:1721
 wb_writeback+0x27d/0x660 fs/fs-writeback.c:1894
 wb_do_writeback+0x101/0x5d0 fs/fs-writeback.c:2039
 wb_workfn+0xb8/0x410 fs/fs-writeback.c:2080
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 21 Comm: kworker/u4:1 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
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