[RFC] mm: why we should clear page when do anonymous page fault

[Xishi Qiu]

handle_pte_fault()
        do_anonymous_page()
                alloc_zeroed_user_highpage_movable()

We will alloc a zeroed page when do anonymous page fault, I don't know
why should clear it? just for safe?

If user space program do like the following, there are two memset 0, right?
kernel alloc zeroed page, and user memset 0 it again, this will waste a
lot of time.

main()
{
        ...
        vaddr = malloc(size)
        if (vaddr)
                memset(vaddr, 0, size);
        ...
}


Thanks,
Xishi Qiu