mm: introduce zap_nonpresent_ptes()

Similar to zap_present_ptes(), let's introduce zap_nonpresent_ptes() to
handle non-present ptes, which can improve code readability.

No functional change.

Link: https://lkml.kernel.org/r/009ca882036d9c7a9f815489cfeafe0bdb79d62d.1733305182.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Jann Horn <jannh@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index f49eb4d4be7586a553d9369eddbdb3eee7306484..bed55f8873d5deb59a743c935c52ab239bebe9a3 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1587,6 +1587,76 @@ static inline int zap_present_ptes(struct mmu_gather *tlb,
        return 1;
 }
 
+static inline int zap_nonpresent_ptes(struct mmu_gather *tlb,
+               struct vm_area_struct *vma, pte_t *pte, pte_t ptent,
+               unsigned int max_nr, unsigned long addr,
+               struct zap_details *details, int *rss)
+{
+       swp_entry_t entry;
+       int nr = 1;
+
+       entry = pte_to_swp_entry(ptent);
+       if (is_device_private_entry(entry) ||
+               is_device_exclusive_entry(entry)) {
+               struct page *page = pfn_swap_entry_to_page(entry);
+               struct folio *folio = page_folio(page);
+
+               if (unlikely(!should_zap_folio(details, folio)))
+                       return 1;
+               /*
+                * Both device private/exclusive mappings should only
+                * work with anonymous page so far, so we don't need to
+                * consider uffd-wp bit when zap. For more information,
+                * see zap_install_uffd_wp_if_needed().
+                */
+               WARN_ON_ONCE(!vma_is_anonymous(vma));
+               rss[mm_counter(folio)]--;
+               if (is_device_private_entry(entry))
+                       folio_remove_rmap_pte(folio, page, vma);
+               folio_put(folio);
+       } else if (!non_swap_entry(entry)) {
+               /* Genuine swap entries, hence a private anon pages */
+               if (!should_zap_cows(details))
+                       return 1;
+
+               nr = swap_pte_batch(pte, max_nr, ptent);
+               rss[MM_SWAPENTS] -= nr;
+               free_swap_and_cache_nr(entry, nr);
+       } else if (is_migration_entry(entry)) {
+               struct folio *folio = pfn_swap_entry_folio(entry);
+
+               if (!should_zap_folio(details, folio))
+                       return 1;
+               rss[mm_counter(folio)]--;
+       } else if (pte_marker_entry_uffd_wp(entry)) {
+               /*
+                * For anon: always drop the marker; for file: only
+                * drop the marker if explicitly requested.
+                */
+               if (!vma_is_anonymous(vma) && !zap_drop_markers(details))
+                       return 1;
+       } else if (is_guard_swp_entry(entry)) {
+               /*
+                * Ordinary zapping should not remove guard PTE
+                * markers. Only do so if we should remove PTE markers
+                * in general.
+                */
+               if (!zap_drop_markers(details))
+                       return 1;
+       } else if (is_hwpoison_entry(entry) || is_poisoned_swp_entry(entry)) {
+               if (!should_zap_cows(details))
+                       return 1;
+       } else {
+               /* We should have covered all the swap entry types */
+               pr_alert("unrecognized swap entry 0x%lx\n", entry.val);
+               WARN_ON_ONCE(1);
+       }
+       clear_not_present_full_ptes(vma->vm_mm, addr, pte, nr, tlb->fullmm);
+       zap_install_uffd_wp_if_needed(vma, addr, pte, nr, details, ptent);
+
+       return nr;
+}
+
 static unsigned long zap_pte_range(struct mmu_gather *tlb,
                                struct vm_area_struct *vma, pmd_t *pmd,
                                unsigned long addr, unsigned long end,
@@ -1598,7 +1668,6 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
        spinlock_t *ptl;
        pte_t *start_pte;
        pte_t *pte;
-       swp_entry_t entry;
        int nr;
 
        tlb_change_page_size(tlb, PAGE_SIZE);
@@ -1611,8 +1680,6 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
        arch_enter_lazy_mmu_mode();
        do {
                pte_t ptent = ptep_get(pte);
-               struct folio *folio;
-               struct page *page;
                int max_nr;
 
                nr = 1;
@@ -1622,8 +1689,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
                if (need_resched())
                        break;
 
+               max_nr = (end - addr) / PAGE_SIZE;
                if (pte_present(ptent)) {
-                       max_nr = (end - addr) / PAGE_SIZE;
                        nr = zap_present_ptes(tlb, vma, pte, ptent, max_nr,
                                              addr, details, rss, &force_flush,
                                              &force_break);
@@ -1631,67 +1698,10 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
                                addr += nr * PAGE_SIZE;
                                break;
                        }
-                       continue;
-               }
-
-               entry = pte_to_swp_entry(ptent);
-               if (is_device_private_entry(entry) ||
-                   is_device_exclusive_entry(entry)) {
-                       page = pfn_swap_entry_to_page(entry);
-                       folio = page_folio(page);
-                       if (unlikely(!should_zap_folio(details, folio)))
-                               continue;
-                       /*
-                        * Both device private/exclusive mappings should only
-                        * work with anonymous page so far, so we don't need to
-                        * consider uffd-wp bit when zap. For more information,
-                        * see zap_install_uffd_wp_if_needed().
-                        */
-                       WARN_ON_ONCE(!vma_is_anonymous(vma));
-                       rss[mm_counter(folio)]--;
-                       if (is_device_private_entry(entry))
-                               folio_remove_rmap_pte(folio, page, vma);
-                       folio_put(folio);
-               } else if (!non_swap_entry(entry)) {
-                       max_nr = (end - addr) / PAGE_SIZE;
-                       nr = swap_pte_batch(pte, max_nr, ptent);
-                       /* Genuine swap entries, hence a private anon pages */
-                       if (!should_zap_cows(details))
-                               continue;
-                       rss[MM_SWAPENTS] -= nr;
-                       free_swap_and_cache_nr(entry, nr);
-               } else if (is_migration_entry(entry)) {
-                       folio = pfn_swap_entry_folio(entry);
-                       if (!should_zap_folio(details, folio))
-                               continue;
-                       rss[mm_counter(folio)]--;
-               } else if (pte_marker_entry_uffd_wp(entry)) {
-                       /*
-                        * For anon: always drop the marker; for file: only
-                        * drop the marker if explicitly requested.
-                        */
-                       if (!vma_is_anonymous(vma) &&
-                           !zap_drop_markers(details))
-                               continue;
-               } else if (is_guard_swp_entry(entry)) {
-                       /*
-                        * Ordinary zapping should not remove guard PTE
-                        * markers. Only do so if we should remove PTE markers
-                        * in general.
-                        */
-                       if (!zap_drop_markers(details))
-                               continue;
-               } else if (is_hwpoison_entry(entry) ||
-                          is_poisoned_swp_entry(entry)) {
-                       if (!should_zap_cows(details))
-                               continue;
                } else {
-                       /* We should have covered all the swap entry types */
-                       pr_alert("unrecognized swap entry 0x%lx\n", entry.val);
-                       WARN_ON_ONCE(1);
+                       nr = zap_nonpresent_ptes(tlb, vma, pte, ptent, max_nr,
+                                                addr, details, rss);
                }
-               clear_not_present_full_ptes(mm, addr, pte, nr, tlb->fullmm);
-               zap_install_uffd_wp_if_needed(vma, addr, pte, nr, details, ptent);
        } while (pte += nr, addr += PAGE_SIZE * nr, addr != end);
 
        add_mm_rss_vec(mm, rss);