syzbot

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BUG: KCSAN: data-race in write_cache_pages / write_cache_pages

write to 0xffff88810041dc78 of 8 bytes by task 1823 on cpu 1:
 write_cache_pages+0xa3a/0xa80 mm/page-writeback.c:2294
 generic_writepages+0x7c/0xc0 mm/page-writeback.c:2334
 blkdev_writepages+0x19/0x20 block/fops.c:424
 do_writepages+0x1cb/0x330 mm/page-writeback.c:2352
 filemap_fdatawrite_wbc mm/filemap.c:388 [inline]
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 __filemap_fdatawrite mm/filemap.c:427 [inline]
 filemap_flush+0xd9/0x100 mm/filemap.c:454
 sync_blockdev_nowait+0x32/0x40 block/bdev.c:187
 sync_filesystem+0xdc/0x180 fs/sync.c:60
 ext4_quota_off+0x89/0x1c0 fs/ext4/super.c:6905
 ext4_quota_off_umount fs/ext4/super.c:1173 [inline]
 ext4_put_super+0xe4/0x610 fs/ext4/super.c:1203
 generic_shutdown_super+0xdf/0x250 fs/super.c:462
 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:164
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:183 [inline]
 exit_to_user_mode_prepare+0x122/0x140 kernel/entry/common.c:215
 __syscall_exit_to_user_mode_work kernel/entry/common.c:297 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:308
 do_syscall_64+0x37/0x50 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810041dc78 of 8 bytes by task 8 on cpu 0:
 write_cache_pages+0x117/0xa80 mm/page-writeback.c:2182
 generic_writepages+0x7c/0xc0 mm/page-writeback.c:2334
 blkdev_writepages+0x19/0x20 block/fops.c:424
 do_writepages+0x1cb/0x330 mm/page-writeback.c:2352
 __writeback_single_inode+0x81/0x590 fs/fs-writeback.c:1581
 writeback_sb_inodes+0x677/0xdf0 fs/fs-writeback.c:1854
 __writeback_inodes_wb+0xb0/0x2b0 fs/fs-writeback.c:1923
 wb_writeback+0x280/0x650 fs/fs-writeback.c:2028
 wb_check_background_flush fs/fs-writeback.c:2094 [inline]
 wb_do_writeback+0x51d/0x560 fs/fs-writeback.c:2182
 wb_workfn+0x98/0x400 fs/fs-writeback.c:2209
 process_one_work+0x3e3/0x970 kernel/workqueue.c:2289
 worker_thread+0x638/0xaa0 kernel/workqueue.c:2436
 kthread+0x1bf/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000000 -> 0x000000000000000e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.17.0-syzkaller-13788-gd0d642a5d365-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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