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BUG: KCSAN: data-race in ext4_setattr / mpage_process_page_bufs

write to 0xffff888134ba6ac8 of 8 bytes by task 30622 on cpu 1:
 i_size_write include/linux/fs.h:913 [inline]
 ext4_setattr+0xd7e/0xf20 fs/ext4/inode.c:5451
 notify_change+0x8a3/0xac0 fs/attr.c:410
 do_truncate fs/open.c:64 [inline]
 vfs_truncate+0x2f7/0x380 fs/open.c:110
 do_sys_truncate fs/open.c:133 [inline]
 __do_sys_truncate fs/open.c:145 [inline]
 __se_sys_truncate fs/open.c:143 [inline]
 __x64_sys_truncate+0xb0/0x130 fs/open.c:143
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888134ba6ac8 of 8 bytes by task 30615 on cpu 0:
 i_size_read include/linux/fs.h:891 [inline]
 mpage_process_page_bufs+0x34/0x560 fs/ext4/inode.c:2187
 mpage_prepare_extent_to_map+0x4f6/0x650 fs/ext4/inode.c:2621
 ext4_writepages+0xa78/0x1e80 fs/ext4/inode.c:2793
 do_writepages+0x1cb/0x330 mm/page-writeback.c:2364
 filemap_fdatawrite_wbc mm/filemap.c:407 [inline]
 __filemap_fdatawrite_range mm/filemap.c:440 [inline]
 file_write_and_wait_range+0x132/0x1d0 mm/filemap.c:824
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:182
 generic_write_sync include/linux/fs.h:2955 [inline]
 ext4_buffered_write_iter+0x322/0x380 fs/ext4/file.c:277
 ext4_file_write_iter+0x2e7/0x1200
 call_write_iter include/linux/fs.h:2162 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x7f5/0x950 fs/read_write.c:590
 ksys_write+0xd9/0x190 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000170000 -> 0x0000000000000081

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30615 Comm: syz-executor.1 Not tainted 5.16.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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