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BUG: KCSAN: data-race in delete_from_page_cache_batch / page_mapping

write to 0xffffea0002a1b758 of 8 bytes by task 5182 on cpu 1:
 page_cache_delete_batch mm/filemap.c:326 [inline]
 delete_from_page_cache_batch+0x672/0x780 mm/filemap.c:357
 truncate_inode_pages_range+0x52f/0x1010 mm/truncate.c:366
 truncate_inode_pages+0x2a/0x40 mm/truncate.c:476
 kill_bdev+0x7f/0xa0 fs/block_dev.c:86
 set_blocksize+0x18e/0x1c0 fs/block_dev.c:136
 sb_set_blocksize+0x3d/0xc0 fs/block_dev.c:145
 sb_min_blocksize+0x95/0xb0 fs/block_dev.c:161
 ext4_fill_super+0x368/0x7a40 fs/ext4/super.c:3686
 mount_bdev+0x264/0x2d0 fs/super.c:1417
 ext4_mount+0x38/0x50 fs/ext4/super.c:6077
 legacy_get_tree+0x78/0xf0 fs/fs_context.c:622
 vfs_get_tree+0x52/0x190 fs/super.c:1547
 do_new_mount fs/namespace.c:2822 [inline]
 do_mount+0xff0/0x14d0 fs/namespace.c:3107
 __do_sys_mount fs/namespace.c:3316 [inline]
 __se_sys_mount fs/namespace.c:3293 [inline]
 __x64_sys_mount+0x12b/0x1a0 fs/namespace.c:3293
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffea0002a1b758 of 8 bytes by task 5183 on cpu 0:
 page_mapping+0x178/0x290 mm/util.c:675
 page_evictable+0x37/0x100 mm/vmscan.c:4295
 __pagevec_lru_add_fn+0xe0/0x820 mm/swap.c:963
 pagevec_lru_move_fn+0xf5/0x170 mm/swap.c:211
 __pagevec_lru_add mm/swap.c:987 [inline]
 __lru_cache_add+0x119/0x1c0 mm/swap.c:411
 lru_cache_add_anon+0x98/0x120 mm/swap.c:423
 shmem_getpage_gfp+0x4d4/0x14c0 mm/shmem.c:1885
 shmem_getpage mm/shmem.c:154 [inline]
 shmem_file_read_iter+0x221/0x730 mm/shmem.c:2565
 call_read_iter include/linux/fs.h:1895 [inline]
 do_iter_readv_writev+0x570/0x5d0 fs/read_write.c:691
 do_iter_read+0x1e4/0x3a0 fs/read_write.c:933
 vfs_iter_read+0x56/0x80 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+0x8d3/0x1514 drivers/block/loop.c:1966
 kthread_worker_fn+0x1d0/0x3c0 kernel/kthread.c:671
 loop_kthread_worker_fn+0x49/0x60 drivers/block/loop.c:901
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5183 Comm: loop2 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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