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BUG: KCSAN: data-race in __do_page_cache_readahead / truncate_setsize

write to 0xffff888120ffe4c0 of 8 bytes by task 20593 on cpu 0:
 i_size_write include/linux/fs.h:894 [inline]
 truncate_setsize+0x34/0x80 mm/truncate.c:839
 fat_setattr+0x7c5/0x810 fs/fat/file.c:536
 notify_change+0x82b/0xad0 fs/attr.c:336
 do_truncate+0xf9/0x180 fs/open.c:64
 handle_truncate fs/namei.c:2887 [inline]
 do_open fs/namei.c:3233 [inline]
 path_openat+0x1e51/0x23d0 fs/namei.c:3346
 do_filp_open+0x11e/0x1b0 fs/namei.c:3373
 do_sys_openat2+0x52e/0x680 fs/open.c:1148
 do_sys_open+0xa2/0x110 fs/open.c:1164
 ksys_open include/linux/syscalls.h:1386 [inline]
 __do_sys_creat fs/open.c:1232 [inline]
 __se_sys_creat fs/open.c:1230 [inline]
 __x64_sys_creat+0x42/0x60 fs/open.c:1230
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888120ffe4c0 of 8 bytes by task 20587 on cpu 1:
 __do_page_cache_readahead+0x80/0x380 mm/readahead.c:165
 ra_submit mm/internal.h:62 [inline]
 ondemand_readahead+0x369/0x730 mm/readahead.c:492
 page_cache_sync_readahead+0x1b0/0x1e0 mm/readahead.c:527
 generic_file_buffered_read mm/filemap.c:2036 [inline]
 generic_file_read_iter+0xf24/0x18c0 mm/filemap.c:2309
 call_read_iter include/linux/fs.h:1901 [inline]
 generic_file_splice_read+0x2df/0x470 fs/splice.c:313
 do_splice_to+0xc7/0x100 fs/splice.c:892
 splice_direct_to_actor+0x1b9/0x540 fs/splice.c:971
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x380/0x800 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1582 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1568
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20587 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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