Re: [PATCH v1 2/4] mm/hugetlb: fix two comments related to huge_pmd_unshare()

[Oscar Salvador]

On Fri, Dec 05, 2025 at 10:35:56PM +0100, David Hildenbrand (Red Hat) wrote:
> Ever since we stopped using the page count to detect shared PMD
> page tables, these comments are outdated.
> 
> The only reason we have to flush the TLB early is because once we drop
> the i_mmap_rwsem, the previously shared page table could get freed (to
> then get reallocated and used for other purpose). So we really have to
> flush the TLB before that could happen.
> 
> So let's simplify the comments a bit.
> 
> The "If we unshared PMDs, the TLB flush was not recorded in mmu_gather."
> part introduced as in commit a4a118f2eead ("hugetlbfs: flush TLBs
> correctly after huge_pmd_unshare") was confusing: sure it is recorded
> in the mmu_gather, otherwise tlb_flush_mmu_tlbonly() wouldn't do
> anything. So let's drop that comment while at it as well.
> 
> We'll centralize these comments in a single helper as we rework the code
> next.
> 
> Fixes: 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count")
> Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>

Acked-by: Oscar Salvador <osalvador@xxxxxxx>


-- 
Oscar Salvador
SUSE Labs