Re: [PATCH 1/1] mm/hugetlb: Make huge_pte_offset() consistent and document behaviour

[Catalin Marinas]

On Tue, Jul 25, 2017 at 04:41:14PM +0100, Punit Agrawal wrote:
> When walking the page tables to resolve an address that points to
> !p*d_present() entry, huge_pte_offset() returns inconsistent values
> depending on the level of page table (PUD or PMD).
> 
> It returns NULL in the case of a PUD entry while in the case of a PMD
> entry, it returns a pointer to the page table entry.
> 
> A similar inconsitency exists when handling swap entries - returns NULL
> for a PUD entry while a pointer to the pte_t is retured for the PMD
> entry.
> 
> Update huge_pte_offset() to make the behaviour consistent - return NULL
> in the case of p*d_none() and a pointer to the pte_t for hugepage or
> swap entries.
> 
> Document the behaviour to clarify the expected behaviour of this
> function. This is to set clear semantics for architecture specific
> implementations of huge_pte_offset().
> 
> Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>

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