Re: [PATCH v3 15/47] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp()

[Baolin Wang]

On 10/31/26 5:39 PM, David Hildenbrand (Arm) wrote:
> From: Josef Bacik <josef@xxxxxxxxxxxxxx>
>
> try_collapse_pte_mapped_thp() drops the PTE lock after it has cleared the
> page table, and takes the PMD lock and the PTE lock to remove it.
>
> In between, MADV_DONTNEED with CONFIG_PT_RECLAIM can reclaim the
> page table. The pmd_same() check is supposed to handle this, but it is
> only done with CONFIG_SPLIT_PTE_PTLOCKS.
>
> Fix it by performing the check unconditionally.
>
> Fix generated by an LLM and sent by Josef Bacik in private.
>
> Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> [ david: adjust description ]
> Reviewed-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> Tested-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> Tested-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
> Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>