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BUG: KCSAN: data-race in __lru_cache_add / lru_add_drain_all

write to 0xffff88812c129b60 of 1 bytes by task 31149 on cpu 1:
 pagevec_add include/linux/pagevec.h:81 [inline]
 __lru_cache_add+0xbf/0x1d0 mm/swap.c:410
 lru_cache_add_anon+0x9e/0x130 mm/swap.c:423
 shmem_getpage_gfp+0x470/0x1390 mm/shmem.c:1885
 shmem_getpage mm/shmem.c:154 [inline]
 shmem_file_read_iter+0x224/0x720 mm/shmem.c:2565
 call_read_iter include/linux/fs.h:1895 [inline]
 do_iter_readv_writev+0x54b/0x5b0 fs/read_write.c:691
 do_iter_read+0x1fc/0x3d0 fs/read_write.c:933
 vfs_iter_read+0x5c/0x80 fs/read_write.c:975
 lo_read_simple drivers/block/loop.c:351 [inline]
 do_req_filebacked drivers/block/loop.c:625 [inline]
 loop_handle_cmd drivers/block/loop.c:1952 [inline]
 loop_queue_work+0x92c/0x1623 drivers/block/loop.c:1966
 kthread_worker_fn+0x1c3/0x3a0 kernel/kthread.c:671
 loop_kthread_worker_fn+0x50/0x70 drivers/block/loop.c:901
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88812c129b60 of 1 bytes by task 31155 on cpu 0:
 lru_add_drain_all+0x17e/0x3d0 mm/swap.c:746
 invalidate_bdev+0x6e/0x90 fs/block_dev.c:97
 __loop_clr_fd+0x250/0x740 drivers/block/loop.c:1140
 loop_clr_fd drivers/block/loop.c:1237 [inline]
 lo_ioctl+0x24c/0xc70 drivers/block/loop.c:1606
 __blkdev_driver_ioctl block/ioctl.c:321 [inline]
 blkdev_ioctl+0x19c/0x400 block/ioctl.c:717
 block_ioctl+0x95/0xc0 fs/block_dev.c:1983
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x109/0x150 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:770
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 31155 Comm: syz-executor.2 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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