MapToError should give back the UnusedPhysFrame on PageAlreadyMapped

[haraldh]

x86_64/src/structures/paging/mapper/mod.rs

Lines 159 to 168 in c94759c

	pub enum MapToError {
	/// An additional frame was needed for the mapping process, but the frame allocator
	/// returned `None`.
	FrameAllocationFailed,
	/// An upper level page table entry has the `HUGE_PAGE` flag set, which means that the
	/// given page is part of an already mapped huge page.
	ParentEntryHugePage,
	/// The given page is already mapped to a physical frame.
	PageAlreadyMapped,
	}

should probably be

pub enum MapToError<S: PageSize> {
    /// An additional frame was needed for the mapping process, but the frame allocator
    /// returned `None`.
    FrameAllocationFailed,
    /// An upper level page table entry has the `HUGE_PAGE` flag set, which means that the
    /// given page is part of an already mapped huge page.
    ParentEntryHugePage,
    /// The given page is already mapped to a physical frame.
    PageAlreadyMapped(UnusedPhysFrame<S>),
}

and methods returning PageAlreadyMapped should give back the frame.

[phil-opp]

Good idea! I would be happy to merge a PR for this.