kernel page

vm_insert_page - insert single page into user vma : user vma to map to : target user address of this page

This allows drivers to insert individual pages they've allocated into a user vma.

The page has to be a nice clean individual kernel allocation. If you allocate a compound page, you need to have marked it as such (__GFP_COMP), or manually just split the page up yourself (see split_page()).

NOTE! Traditionally this was done with "remap_pfn_range()" which took an arbitrary page protection parameter. This doesn't allow that. Your vma protection will have to be set up correctly, which means that if you want a shared writable mapping, you'd better ask for a shared writable mapping!

The page does not need to be reserved.

Usually this function is called from f_op->mmap() handler under mm->mmap_sem write-lock, so it can change vma->vm_flags. Caller must set VM_MIXEDMAP on vma if it wants to call this function from other places, for example from page-fault handler.