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BUG: KCSAN: data-race in ext4_setattr / generic_file_read_iter

write to 0xffff888125573630 of 8 bytes by task 20442 on cpu 0:
 i_size_write include/linux/fs.h:888 [inline]
 ext4_setattr+0xd58/0x1290 fs/ext4/inode.c:5340
 notify_change+0x82b/0xb00 fs/attr.c:336
 do_truncate+0xf9/0x180 fs/open.c:64
 handle_truncate fs/namei.c:3083 [inline]
 do_last fs/namei.c:3496 [inline]
 path_openat+0x1241/0x2f70 fs/namei.c:3607
 do_filp_open+0x11e/0x1b0 fs/namei.c:3637
 do_sys_openat2+0x4f5/0x620 fs/open.c:1149
 do_sys_open+0xa2/0x110 fs/open.c:1165
 ksys_open include/linux/syscalls.h:1386 [inline]
 __do_sys_creat fs/open.c:1233 [inline]
 __se_sys_creat fs/open.c:1231 [inline]
 __x64_sys_creat+0x42/0x60 fs/open.c:1231
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888125573630 of 8 bytes by task 20448 on cpu 1:
 generic_file_buffered_read mm/filemap.c:2084 [inline]
 generic_file_read_iter+0x85b/0x1490 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x103/0x360 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [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+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1575 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0xb8/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20448 Comm: syz-executor.1 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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