https://lkml.iu.edu/1401.3/00089.html
Linux-Kernel Archive: Re: [PATCH] mm: Ignore VM_SOFTDIRTY on VMA merging, v2
https://rust.docs.kernel.org/kernel/mm/virt/flags/constant.SOFTDIRTY.html
SOFTDIRTY in kernel::mm::virt::flags - Rust
Not soft dirty clean area.
kernelmmvirtflagsrust