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BUG: KCSAN: data-race in ext4_setattr / filemap_read

write to 0xffff8881261ce2e8 of 8 bytes by task 29104 on cpu 1:
 i_size_write include/linux/fs.h:911 [inline]
 ext4_setattr+0xd7f/0xef0 fs/ext4/inode.c:5480
 notify_change+0x8a3/0xac0 fs/attr.c:398
 do_truncate fs/open.c:64 [inline]
 do_sys_ftruncate+0x2d9/0x390 fs/open.c:192
 __do_sys_ftruncate fs/open.c:203 [inline]
 __se_sys_ftruncate fs/open.c:201 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:201
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881261ce2e8 of 8 bytes by task 29117 on cpu 0:
 i_size_read include/linux/fs.h:889 [inline]
 filemap_read+0xd45/0x1210 mm/filemap.c:2643
 generic_file_read_iter+0x75/0x2c0 mm/filemap.c:2782
 ext4_file_read_iter+0x1db/0x290 fs/ext4/file.c:73
 call_read_iter include/linux/fs.h:2152 [inline]
 generic_file_splice_read+0x22c/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x618/0xb90 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000003c18200 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29117 Comm: syz-executor.5 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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