Extend core huge page management functions to handle device-private THP
entries. This enables proper handling of large device-private folios in
fundamental MM operations.
The following functions have been updated:
- copy_huge_pmd(): Handle device-private entries during fork/clone
- zap_huge_pmd(): Properly free device-private THP during munmap
- change_huge_pmd(): Support protection changes on device-private THP
- __pte_offset_map(): Add device-private entry awareness
Cc: David Hildenbrand <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: Ying Huang <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Simona Vetter <[email protected]>
Cc: Ralph Campbell <[email protected]>
Cc: Mika Penttilä <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Francois Dugast <[email protected]>
Cc: Andrew Morton <[email protected]>
Acked-by: Zi Yan <[email protected]>
Signed-off-by: Matthew Brost <[email protected]>
Signed-off-by: Balbir Singh <[email protected]>
---
include/linux/swapops.h | 32 +++++++++++++++++++++++
mm/huge_memory.c | 56 ++++++++++++++++++++++++++++++++++-------
mm/pgtable-generic.c | 2 +-
3 files changed, 80 insertions(+), 10 deletions(-)
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 64ea151a7ae3..2687928a8146 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -594,10 +594,42 @@ static inline int is_pmd_migration_entry(pmd_t pmd)
}
#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
+#if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_ARCH_ENABLE_THP_MIGRATION)
+
+/**
+ * is_pmd_device_private_entry() - Check if PMD contains a device private swap
entry
+ * @pmd: The PMD to check
+ *
+ * Returns true if the PMD contains a swap entry that represents a device
private
+ * page mapping. This is used for zone device private pages that have been
+ * swapped out but still need special handling during various memory management
+ * operations.
+ *
+ * Return: 1 if PMD contains device private entry, 0 otherwise
+ */
+static inline int is_pmd_device_private_entry(pmd_t pmd)
+{
+ return is_swap_pmd(pmd) &&
is_device_private_entry(pmd_to_swp_entry(pmd));
+}
+
+#else /* CONFIG_ZONE_DEVICE && CONFIG_ARCH_ENABLE_THP_MIGRATION */
+
+static inline int is_pmd_device_private_entry(pmd_t pmd)
+{
+ return 0;
+}
+
+#endif /* CONFIG_ZONE_DEVICE && CONFIG_ARCH_ENABLE_THP_MIGRATION */
+
static inline int non_swap_entry(swp_entry_t entry)
{
return swp_type(entry) >= MAX_SWAPFILES;
}
+static inline int is_pmd_non_present_folio_entry(pmd_t pmd)
+{
+ return is_pmd_migration_entry(pmd) || is_pmd_device_private_entry(pmd);
+}
+
#endif /* CONFIG_MMU */
#endif /* _LINUX_SWAPOPS_H */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1b81680b4225..8e0a1747762d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1703,17 +1703,45 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct
mm_struct *src_mm,
if (unlikely(is_swap_pmd(pmd))) {
swp_entry_t entry = pmd_to_swp_entry(pmd);
- VM_BUG_ON(!is_pmd_migration_entry(pmd));
- if (!is_readable_migration_entry(entry)) {
- entry = make_readable_migration_entry(
- swp_offset(entry));
+ VM_WARN_ON(!is_pmd_non_present_folio_entry(pmd));
+
+ if (is_writable_migration_entry(entry) ||
+ is_readable_exclusive_migration_entry(entry)) {
+ entry =
make_readable_migration_entry(swp_offset(entry));
pmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*src_pmd))
pmd = pmd_swp_mksoft_dirty(pmd);
if (pmd_swp_uffd_wp(*src_pmd))
pmd = pmd_swp_mkuffd_wp(pmd);
set_pmd_at(src_mm, addr, src_pmd, pmd);
+ } else if (is_device_private_entry(entry)) {
+ /*
+ * For device private entries, since there are no
+ * read exclusive entries, writable = !readable
+ */
+ if (is_writable_device_private_entry(entry)) {
+ entry =
make_readable_device_private_entry(swp_offset(entry));
+ pmd = swp_entry_to_pmd(entry);
+
+ if (pmd_swp_soft_dirty(*src_pmd))
+ pmd = pmd_swp_mksoft_dirty(pmd);
+ if (pmd_swp_uffd_wp(*src_pmd))
+ pmd = pmd_swp_mkuffd_wp(pmd);
+ set_pmd_at(src_mm, addr, src_pmd, pmd);
+ }
+
+ src_folio = pfn_swap_entry_folio(entry);
+ VM_WARN_ON(!folio_test_large(src_folio));
+
+ folio_get(src_folio);
+ /*
+ * folio_try_dup_anon_rmap_pmd does not fail for
+ * device private entries.
+ */
+ folio_try_dup_anon_rmap_pmd(src_folio, &src_folio->page,
+ dst_vma, src_vma);
}
+
add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
mm_inc_nr_ptes(dst_mm);
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
@@ -2211,15 +2239,16 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct
vm_area_struct *vma,
folio_remove_rmap_pmd(folio, page, vma);
WARN_ON_ONCE(folio_mapcount(folio) < 0);
VM_BUG_ON_PAGE(!PageHead(page), page);
- } else if (thp_migration_supported()) {
+ } else if (is_pmd_non_present_folio_entry(orig_pmd)) {
swp_entry_t entry;
- VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
entry = pmd_to_swp_entry(orig_pmd);
folio = pfn_swap_entry_folio(entry);
flush_needed = 0;
- } else
- WARN_ONCE(1, "Non present huge pmd without pmd migration
enabled!");
+
+ if (!thp_migration_supported())
+ WARN_ONCE(1, "Non present huge pmd without pmd
migration enabled!");
+ }
if (folio_test_anon(folio)) {
zap_deposited_table(tlb->mm, pmd);
@@ -2239,6 +2268,12 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct
vm_area_struct *vma,
folio_mark_accessed(folio);
}
+ if (folio_is_device_private(folio)) {
+ folio_remove_rmap_pmd(folio, &folio->page, vma);
+ WARN_ON_ONCE(folio_mapcount(folio) < 0);
+ folio_put(folio);
+ }
