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BUG: KCSAN: data-race in do_mpage_readpage / truncate_setsize

write to 0xffff88810d547a50 of 8 bytes by task 4013 on cpu 0:
 i_size_write include/linux/fs.h:871 [inline]
 truncate_setsize+0x2a/0xc0 mm/truncate.c:861
 fat_setattr+0x623/0x740 fs/fat/file.c:536
 notify_change+0x7b3/0xa50 fs/attr.c:336
 do_truncate+0xe0/0x120 fs/open.c:64
 handle_truncate fs/namei.c:2910 [inline]
 do_open fs/namei.c:3256 [inline]
 path_openat+0x1a37/0x20a0 fs/namei.c:3369
 do_filp_open+0xbd/0x1d0 fs/namei.c:3396
 do_sys_openat2+0xa3/0x240 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_creat fs/open.c:1258 [inline]
 __se_sys_creat fs/open.c:1252 [inline]
 __x64_sys_creat+0x62/0x80 fs/open.c:1252
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810d547a50 of 8 bytes by task 4005 on cpu 1:
 i_size_read include/linux/fs.h:849 [inline]
 do_mpage_readpage+0x14e/0x1030 fs/mpage.c:191
 mpage_readahead+0x157/0x340 fs/mpage.c:391
 fat_readahead+0x18/0x20 fs/fat/inode.c:215
 read_pages+0xa0/0x6e0 mm/readahead.c:130
 page_cache_ra_unbounded+0x464/0x4c0 mm/readahead.c:238
 ondemand_readahead+0x560/0x780 mm/readahead.c:267
 page_cache_sync_ra+0x1ab/0x1c0 mm/readahead.c:577
 page_cache_sync_readahead include/linux/pagemap.h:839 [inline]
 generic_file_buffered_read+0x38d/0x2110 mm/filemap.c:2227
 generic_file_read_iter+0x80/0x3d0 mm/filemap.c:2535
 call_read_iter include/linux/fs.h:1881 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:788 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x574/0xb70 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 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: 1 PID: 4005 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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