Today, I have read through some documents about file system (http://tekrants.me/2014/07/14/linux-file-system-write/). And the term kernel page is mentioned several times in this article. I am now quite confused about the memory usage of kernel and of user.
I understand that the address space for kernel and user and between users are different. The virtual to physical mapping is independent with each other. Is the memory mapped to kernel address space cannot be mapped to any user address space?
And, for the article I mentioned above, it basically talks about the usage of page cache. So, when the operating system is asked to load some data or code from disk to the page cache, where should those pages holding the data and code come from? And can those pages be accessed by users?