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BUG: KCSAN: data-race in delete_from_page_cache_batch / nr_blockdev_pages

write to 0xffff8881206f1ed0 of 8 bytes by task 24273 on cpu 1:
 page_cache_delete_batch mm/filemap.c:340 [inline]
 delete_from_page_cache_batch+0x5d1/0x850 mm/filemap.c:358
 truncate_inode_pages_range+0x482/0xf70 mm/truncate.c:366
 blkdev_fallocate+0x1e3/0x2e0 fs/block_dev.c:2001
 vfs_fallocate+0x43c/0x5d0 fs/open.c:309
 madvise_remove mm/madvise.c:857 [inline]
 madvise_vma mm/madvise.c:940 [inline]
 do_madvise+0x83d/0x14e0 mm/madvise.c:1145
 __do_sys_madvise mm/madvise.c:1171 [inline]
 __se_sys_madvise mm/madvise.c:1169 [inline]
 __x64_sys_madvise+0x3e/0x50 mm/madvise.c:1169
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881206f1ed0 of 8 bytes by task 24275 on cpu 0:
 nr_blockdev_pages+0x7c/0xd0 fs/block_dev.c:914
 si_meminfo+0x3a/0x60 mm/page_alloc.c:5263
 meminfo_proc_show+0x37/0xc40 fs/proc/meminfo.c:42
 seq_read+0x2ee/0x900 fs/seq_file.c:208
 pde_read fs/proc/inode.c:306 [inline]
 proc_reg_read+0x116/0x1a0 fs/proc/inode.c:318
 do_loop_readv_writev fs/read_write.c:734 [inline]
 do_iter_read+0x3d2/0x4b0 fs/read_write.c:955
 vfs_readv fs/read_write.c:1073 [inline]
 do_preadv+0x13b/0x230 fs/read_write.c:1165
 __do_sys_preadv fs/read_write.c:1215 [inline]
 __se_sys_preadv fs/read_write.c:1210 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1210
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24275 Comm: syz-executor.5 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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