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zsj1z22kB9MidJJU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 25 Apr 2025, at 7:23, David Hildenbrand wrote: > On 25.04.25 13:10, Zi Yan wrote: >> On 25 Apr 2025, at 6:38, Gavin Guo wrote: >> >>> The split_huge_pmd_locked function currently performs redundant check= s >>> for migration entries and folio validation that are already handled b= y >>> the page_vma_mapped_walk mechanism in try_to_migrate_one. >>> >>> Specifically, page_vma_mapped_walk already ensures that: >>> - The folio is properly mapped in the given VMA area >>> - pmd_trans_huge, pmd_devmap, and migration entry validation are >>> performed >>> >>> To leverage page_vma_mapped_walk's work, moving TTU_SPLIT_HUGE_PMD >>> handling to the while loop checking and removing these duplicate chec= ks >>> from split_huge_pmd_locked. >>> >>> Suggested-by: David Hildenbrand >>> Link: https://lore.kernel.org/all/98d1d195-7821-4627-b518-83103ade56c= 0@redhat.com/ >>> Link: https://lore.kernel.org/all/91599a3c-e69e-4d79-bac5-5013c96203d= 7@redhat.com/ >>> Signed-off-by: Gavin Guo >>> Acked-by: David Hildenbrand >>> --- > >> >> I wonder if we need a WARN here to make sure when THP migration suppor= t is not >> present all PMDs are split in try_to_migrate_one(). > > Can you elaborate on the condition you have in mind? > > If we have TTU_SPLIT_HUGE_PMD set, we'll never reach that point. > > Without CONFIG_ARCH_ENABLE_THP_MIGRATION, we should be running into the= > VM_BUG_ON_FOLIO(!pvmw.pte, folio); > > right? Right. Missed that code, which is right at the bottom. Sorry about that. Thank you for pointing this out. OK, please disregard my comments. The patch is good in current form. -- Best Regards, Yan, Zi