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BUG: KCSAN: data-race in __writeback_single_inode / iput

read-write to 0xffff8881004810b8 of 8 bytes by task 28980 on cpu 0:
 __writeback_single_inode+0x201/0x860 fs/fs-writeback.c:1639
 writeback_single_inode+0x12f/0x4a0 fs/fs-writeback.c:1724
 write_inode_now+0xcc/0xf0 fs/fs-writeback.c:2766
 bdev_write_inode block/bdev.c:57 [inline]
 blkdev_flush_mapping+0x124/0x1c0 block/bdev.c:631
 blkdev_put_whole block/bdev.c:661 [inline]
 blkdev_put+0x33a/0x470 block/bdev.c:898
 kill_block_super+0x47/0x60 fs/super.c:1649
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7305
 deactivate_locked_super+0x73/0x1c0 fs/super.c:481
 deactivate_super+0x9b/0xb0 fs/super.c:514
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1254
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1261
 task_work_run+0x135/0x1a0 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xd1/0xe0 kernel/entry/common.c:171
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881004810b8 of 8 bytes by task 6007 on cpu 1:
 iput+0x32/0x5b0 fs/inode.c:1791
 blkdev_get_no_open+0xaf/0xe0 block/bdev.c:722
 blkdev_get_by_dev+0x64/0x390 block/bdev.c:767
 blkdev_open+0xf7/0x1e0 block/fops.c:589
 do_dentry_open+0x5c3/0xae0 fs/open.c:929
 vfs_open+0x4a/0x50 fs/open.c:1063
 do_open fs/namei.c:3639 [inline]
 path_openat+0x17f2/0x1d10 fs/namei.c:3796
 do_filp_open+0xf6/0x200 fs/namei.c:3823
 do_sys_openat2+0xab/0x110 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000084 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6007 Comm: udevd Not tainted 6.5.0-syzkaller-10885-g0468be89b3fa #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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I/O error, dev loop2, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2