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BUG: KCSAN: data-race in lo_ioctl / loop_queue_work

write to 0xffff88821aa7d818 of 4 bytes by task 12873 on cpu 1:
 loop_clr_fd drivers/block/loop.c:1252 [inline]
 lo_ioctl+0x62c/0xc50 drivers/block/loop.c:1628
 __blkdev_driver_ioctl block/ioctl.c:322 [inline]
 blkdev_ioctl+0x1a1/0x420 block/ioctl.c:718
 block_ioctl+0x91/0xb0 fs/block_dev.c:1996
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x101/0x150 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88821aa7d818 of 4 bytes by task 12875 on cpu 0:
 loop_handle_cmd drivers/block/loop.c:1969 [inline]
 loop_queue_work+0xa4/0x14b9 drivers/block/loop.c:1991
 kthread_worker_fn+0x1d0/0x3c0 kernel/kthread.c:684
 loop_kthread_worker_fn+0x49/0x60 drivers/block/loop.c:923
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12875 Comm: loop2 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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