On Mon, Feb 17, 2025 at 02:08:00PM +0000, Ryan Roberts wrote:

A call to vmalloc_huge() may cause memory blocks to be mapped at pmd or
pud level. But it is possible to subsequently call vunmap_range() on a
sub-range of the mapped memory, which partially overlaps a pmd or pud.
In this case, vmalloc unmaps the entire pmd or pud so that the
no-overlapping portion is also unmapped. Clearly that would have a bad
outcome, but it's not something that any callers do today as far as I
can tell. So I guess it's just expected that callers will not do this.

However, it would be useful to know if this happened in future; let's
add a warning to cover the eventuality.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>