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BUG: KCSAN: data-race in __lru_cache_add / lru_add_drain_all

read to 0xffff88812be27620 of 1 bytes by task 27435 on cpu 1:
 lru_add_drain_all+0xf5/0x350 mm/swap.c:728
 invalidate_bdev+0x6e/0x90 fs/block_dev.c:97
 btrfs_close_bdev.part.0+0xa8/0xb0 fs/btrfs/volumes.c:1238
 btrfs_close_bdev fs/btrfs/volumes.c:1233 [inline]
 btrfs_close_one_device fs/btrfs/volumes.c:1262 [inline]
 close_fs_devices.part.0+0x170/0x520 fs/btrfs/volumes.c:1291
 close_fs_devices fs/btrfs/volumes.c:1323 [inline]
 btrfs_close_devices+0x92/0x170 fs/btrfs/volumes.c:1309
 btrfs_mount_root+0xa34/0xb00 fs/btrfs/super.c:1574
 legacy_get_tree+0x7e/0xf0 fs/fs_context.c:647
 vfs_get_tree+0x56/0x1a0 fs/super.c:1545
 fc_mount+0x20/0x80 fs/namespace.c:962
 vfs_kern_mount.part.0+0xe6/0xf0 fs/namespace.c:992
 vfs_kern_mount+0x49/0x70 fs/namespace.c:979
 btrfs_mount+0x250/0xf37 fs/btrfs/super.c:1621
 legacy_get_tree+0x7e/0xf0 fs/fs_context.c:647
 vfs_get_tree+0x56/0x1a0 fs/super.c:1545
 do_new_mount fs/namespace.c:2822 [inline]
 do_mount+0x1004/0x14f0 fs/namespace.c:3142
 ksys_mount+0xe8/0x160 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0x70/0x90 fs/namespace.c:3362
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812be27620 of 1 bytes by task 27439 on cpu 0:
 pagevec_add include/linux/pagevec.h:81 [inline]
 __lru_cache_add+0xbf/0x1d0 mm/swap.c:405
 lru_cache_add_anon+0x9e/0x130 mm/swap.c:418
 shmem_getpage_gfp+0x470/0x1390 mm/shmem.c:1884
 shmem_getpage mm/shmem.c:154 [inline]
 shmem_write_begin+0x9f/0x140 mm/shmem.c:2482
 generic_perform_write+0x136/0x320 mm/filemap.c:3305
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3434
 generic_file_write_iter+0x28c/0x390 mm/filemap.c:3466
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_pwrite64+0xee/0x120 fs/read_write.c:665
 __do_sys_pwrite64 fs/read_write.c:675 [inline]
 __se_sys_pwrite64 fs/read_write.c:672 [inline]
 __x64_sys_pwrite64+0x5e/0x80 fs/read_write.c:672
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 27439 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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