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BUG: KCSAN: data-race in write_cache_pages / write_cache_pages

write to 0xffff88810043cc88 of 8 bytes by task 1829 on cpu 1:
 write_cache_pages+0x9ea/0xa30 mm/page-writeback.c:2385
 generic_writepages+0x7c/0xc0 mm/page-writeback.c:2425
 blkdev_writepages+0x19/0x20 block/fops.c:407
 do_writepages+0x1db/0x350 mm/page-writeback.c:2443
 filemap_fdatawrite_wbc+0xd6/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 __filemap_fdatawrite mm/filemap.c:427 [inline]
 filemap_flush+0x93/0xc0 mm/filemap.c:454
 sync_blockdev_nowait+0x32/0x40 block/bdev.c:187
 sync_filesystem+0xdc/0x180 fs/sync.c:60
 generic_shutdown_super+0x3c/0x240 fs/super.c:445
 kill_block_super+0x4a/0x90 fs/super.c:1394
 deactivate_locked_super+0x6a/0xb0 fs/super.c:332
 deactivate_super+0x85/0x90 fs/super.c:363
 cleanup_mnt+0x267/0x2d0 fs/namespace.c:1186
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1193
 task_work_run+0x8e/0x110 kernel/task_work.c:177
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x124/0x130 kernel/entry/common.c:169
 exit_to_user_mode_prepare kernel/entry/common.c:201 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x6a/0x90 kernel/entry/common.c:294
 do_syscall_64+0x37/0x70 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

write to 0xffff88810043cc88 of 8 bytes by task 31145 on cpu 0:
 write_cache_pages+0x9ea/0xa30 mm/page-writeback.c:2385
 generic_writepages+0x7c/0xc0 mm/page-writeback.c:2425
 blkdev_writepages+0x19/0x20 block/fops.c:407
 do_writepages+0x1db/0x350 mm/page-writeback.c:2443
 __writeback_single_inode+0x81/0x590 fs/fs-writeback.c:1581
 writeback_sb_inodes+0x6a0/0xdd0 fs/fs-writeback.c:1859
 __writeback_inodes_wb+0xb0/0x2a0 fs/fs-writeback.c:1930
 wb_writeback+0x280/0x650 fs/fs-writeback.c:2035
 wb_check_background_flush fs/fs-writeback.c:2101 [inline]
 wb_do_writeback+0x5b3/0x600 fs/fs-writeback.c:2189
 wb_workfn+0x88/0x260 fs/fs-writeback.c:2216
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000000 -> 0x0000000000000013

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 31145 Comm: kworker/u4:6 Not tainted 5.18.0-syzkaller-10139-g8291eaafed36-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-7:5)
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