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BUG: KCSAN: data-race in lru_add_drain_all / lru_cache_add

write to 0xffff888237d26468 of 1 bytes by task 22115 on cpu 1:
 pagevec_add include/linux/pagevec.h:74 [inline]
 lru_cache_add+0x74/0x130 mm/swap.c:461
 shmem_getpage_gfp+0xcf8/0x1410 mm/shmem.c:1934
 shmem_getpage mm/shmem.c:155 [inline]
 shmem_file_read_iter+0x1a2/0x5c0 mm/shmem.c:2607
 call_read_iter include/linux/fs.h:1971 [inline]
 do_iter_readv_writev+0x2e8/0x360 fs/read_write.c:738
 do_iter_read+0x109/0x4b0 fs/read_write.c:801
 vfs_iter_read+0x4c/0x70 fs/read_write.c:843
 lo_read_simple drivers/block/loop.c:360 [inline]
 do_req_filebacked drivers/block/loop.c:636 [inline]
 loop_handle_cmd drivers/block/loop.c:2045 [inline]
 loop_queue_work+0xdfb/0x1330 drivers/block/loop.c:2063
 kthread_worker_fn+0x280/0x4d0 kernel/kthread.c:735
 loop_kthread_worker_fn+0x3e/0x50 drivers/block/loop.c:932
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888237d26468 of 1 bytes by task 1772 on cpu 0:
 pagevec_count include/linux/pagevec.h:61 [inline]
 lru_add_drain_all+0x108/0x3c0 mm/swap.c:813
 invalidate_bdev+0x50/0x70 fs/block_dev.c:96
 ext4_put_super+0x5d0/0x8e0 fs/ext4/super.c:1229
 generic_shutdown_super+0xd5/0x220 fs/super.c:464
 kill_block_super+0x4a/0x90 fs/super.c:1394
 deactivate_locked_super+0x65/0xd0 fs/super.c:335
 deactivate_super+0x85/0x90 fs/super.c:366
 cleanup_mnt+0x277/0x2e0 fs/namespace.c:1136
 __cleanup_mnt+0x15/0x20 fs/namespace.c:1143
 task_work_run+0xae/0x130 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x151/0x170 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x40/0x50 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1772 Comm: syz-executor.0 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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