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BUG: KCSAN: data-race in block_page_mkwrite / generic_write_end

write to 0xffff888134a07268 of 8 bytes by task 5005 on cpu 1:
 i_size_write include/linux/fs.h:913 [inline]
 generic_write_end+0x96/0x180 fs/buffer.c:2186
 ext4_da_write_end+0x448/0x510 fs/ext4/inode.c:3059
 generic_perform_write+0x261/0x400 mm/filemap.c:3765
 ext4_buffered_write_iter+0x196/0x290 fs/ext4/file.c:269
 ext4_file_write_iter+0x22b/0xdc0
 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

read to 0xffff888134a07268 of 8 bytes by task 5007 on cpu 0:
 i_size_read include/linux/fs.h:891 [inline]
 block_page_mkwrite+0xb0/0x320 fs/buffer.c:2509
 ext4_page_mkwrite+0x5f2/0xcb0 fs/ext4/inode.c:6058
 do_page_mkwrite mm/memory.c:2856 [inline]
 wp_page_shared mm/memory.c:3189 [inline]
 do_wp_page+0x785/0xa80 mm/memory.c:3290
 handle_pte_fault mm/memory.c:4569 [inline]
 __handle_mm_fault mm/memory.c:4686 [inline]
 handle_mm_fault+0x975/0x1590 mm/memory.c:4784
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1485 [inline]
 exc_page_fault+0x91/0x290 arch/x86/mm/fault.c:1541
 asm_exc_page_fault+0x1e/0x30
 copy_user_enhanced_fast_string+0xe/0x30
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout lib/iov_iter.c:157 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:228 [inline]
 __copy_page_to_iter lib/iov_iter.c:852 [inline]
 copy_page_to_iter+0x2d9/0x950 lib/iov_iter.c:880
 filemap_read+0x138b/0x16d0 mm/filemap.c:2697
 generic_file_read_iter+0x72/0x2a0 mm/filemap.c:2792
 call_read_iter include/linux/fs.h:2156 [inline]
 do_iter_readv_writev+0x2fb/0x380 fs/read_write.c:723
 do_iter_read+0x192/0x5d0 fs/read_write.c:786
 vfs_readv fs/read_write.c:906 [inline]
 do_preadv+0x159/0x240 fs/read_write.c:998
 __do_sys_preadv fs/read_write.c:1048 [inline]
 __se_sys_preadv fs/read_write.c:1043 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1043
 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: 0x0000000001444000 -> 0x0000000001448000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5007 Comm: syz-executor.0 Not tainted 5.16.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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