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From: Lance Yang In-Reply-To: <1282de5a-3dce-443d-91d1-111103140973@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 7gzirdrj6gc5j853z8s71ochr1ofsy3h X-Rspam-User: X-Rspamd-Queue-Id: BBCA4180005 X-Rspamd-Server: rspam10 X-HE-Tag: 1758714453-674222 X-HE-Meta: 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 Bp6w73Rm KoThZywlMJfJ6OswYOMxeMbSZzCrMRDhWCg3KEc9m4TtWm4lbqIi3P8QVTybf3JgqMV+QGTT4oVg0/76garetkj8TMqe4SiOwEZCx0YdAVTL5xTfumWjMntMX6Fa+y/OtNDGrnvJd55xH8I/8rqbM8baG2/qM4b4HQaMus8JbyoafBI1nxXeGBxVtC9TBomzPxzGTGPMyhV7/Cijm8h2tLmy7kVEEIPu1zZZx07zMx0z7GALgp0CIASeWBusheGZYuQyHDCz8HUMelCBrvSpYL4OaeRz6H0VGLKN5kO/tUnmI3vS04oa84L2qsfeRvSGJtrVm+g2dx1/xZnXL0fcdAmBxVA== 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 2025/9/24 18:10, David Hildenbrand wrote: > On 24.09.25 12:02, Lance Yang wrote: >> From: Lance Yang >> >> The existing check in hpage_collapse_scan_pmd() is specific to uffd-wp >> markers. Other special markers (e.g., GUARD, POISONED) would not be >> caught >> early, leading to failures deeper in the swap-in logic. >> >> hpage_collapse_scan_pmd() >>   `- collapse_huge_page() >>       `- __collapse_huge_page_swapin() -> fails! >> >> As David suggested[1], this patch skips any such non-swap entries early. >> If a special marker is found, the scan is aborted immediately with the >> SCAN_PTE_NON_PRESENT result, as Lorenzo suggested[2], avoiding wasted >> work. > > Note that I suggested to skip all non-present entries except swap > entries, which includes migration entries, hwpoisoned entries etc. Oops, I completely misunderstood your suggestion :( It should be to handle all special non-present entries (migration, hwpoison, markers), not just a specific type of marker ... How about this version, which handles all non-swap entries as you suggested? diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 7ab2d1a42df3..27f432e7f07c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1284,7 +1284,23 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr += PAGE_SIZE) { pte_t pteval = ptep_get(_pte); - if (is_swap_pte(pteval)) { + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + ++none_or_zero; + if (!userfaultfd_armed(vma) && + (!cc->is_khugepaged || + none_or_zero <= khugepaged_max_ptes_none)) { + continue; + } else { + result = SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + goto out_unmap; + } + } else if (!pte_present(pteval)) { + if (non_swap_entry(pte_to_swp_entry(pteval))) { + result = SCAN_PTE_NON_PRESENT; + goto out_unmap; + } + ++unmapped; if (!cc->is_khugepaged || unmapped <= khugepaged_max_ptes_swap) { @@ -1293,7 +1309,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, * enabled swap entries. Please see * comment below for pte_uffd_wp(). */ - if (pte_swp_uffd_wp_any(pteval)) { + if (pte_swp_uffd_wp(pteval)) { result = SCAN_PTE_UFFD_WP; goto out_unmap; } @@ -1304,18 +1320,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, goto out_unmap; } } - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { - ++none_or_zero; - if (!userfaultfd_armed(vma) && - (!cc->is_khugepaged || - none_or_zero <= khugepaged_max_ptes_none)) { - continue; - } else { - result = SCAN_EXCEED_NONE_PTE; - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); - goto out_unmap; - } - } if (pte_uffd_wp(pteval)) { /* * Don't collapse the page if any of the small --- Thanks, Lance