diff options
Diffstat (limited to 'include/linux/rmap.h')
| -rw-r--r-- | include/linux/rmap.h | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index d1e888cc97a5..c131b0efff0f 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -13,6 +13,7 @@ #include <linux/highmem.h> #include <linux/pagemap.h> #include <linux/memremap.h> +#include <linux/bit_spinlock.h> /* * The anon_vma heads a list of private "related" vmas, to scan if @@ -173,6 +174,169 @@ static inline void anon_vma_merge(struct vm_area_struct *vma, struct anon_vma *folio_get_anon_vma(const struct folio *folio); +#ifdef CONFIG_MM_ID +static __always_inline void folio_lock_large_mapcount(struct folio *folio) +{ + bit_spin_lock(FOLIO_MM_IDS_LOCK_BITNUM, &folio->_mm_ids); +} + +static __always_inline void folio_unlock_large_mapcount(struct folio *folio) +{ + __bit_spin_unlock(FOLIO_MM_IDS_LOCK_BITNUM, &folio->_mm_ids); +} + +static inline unsigned int folio_mm_id(const struct folio *folio, int idx) +{ + VM_WARN_ON_ONCE(idx != 0 && idx != 1); + return folio->_mm_id[idx] & MM_ID_MASK; +} + +static inline void folio_set_mm_id(struct folio *folio, int idx, mm_id_t id) +{ + VM_WARN_ON_ONCE(idx != 0 && idx != 1); + folio->_mm_id[idx] &= ~MM_ID_MASK; + folio->_mm_id[idx] |= id; +} + +static inline void __folio_large_mapcount_sanity_checks(const struct folio *folio, + int diff, mm_id_t mm_id) +{ + VM_WARN_ON_ONCE(!folio_test_large(folio) || folio_test_hugetlb(folio)); + VM_WARN_ON_ONCE(diff <= 0); + VM_WARN_ON_ONCE(mm_id < MM_ID_MIN || mm_id > MM_ID_MAX); + + /* + * Make sure we can detect at least one complete PTE mapping of the + * folio in a single MM as "exclusively mapped". This is primarily + * a check on 32bit, where we currently reduce the size of the per-MM + * mapcount to a short. + */ + VM_WARN_ON_ONCE(diff > folio_large_nr_pages(folio)); + VM_WARN_ON_ONCE(folio_large_nr_pages(folio) - 1 > MM_ID_MAPCOUNT_MAX); + + VM_WARN_ON_ONCE(folio_mm_id(folio, 0) == MM_ID_DUMMY && + folio->_mm_id_mapcount[0] != -1); + VM_WARN_ON_ONCE(folio_mm_id(folio, 0) != MM_ID_DUMMY && + folio->_mm_id_mapcount[0] < 0); + VM_WARN_ON_ONCE(folio_mm_id(folio, 1) == MM_ID_DUMMY && + folio->_mm_id_mapcount[1] != -1); + VM_WARN_ON_ONCE(folio_mm_id(folio, 1) != MM_ID_DUMMY && + folio->_mm_id_mapcount[1] < 0); + VM_WARN_ON_ONCE(!folio_mapped(folio) && + folio_test_large_maybe_mapped_shared(folio)); +} + +static __always_inline void folio_set_large_mapcount(struct folio *folio, + int mapcount, struct vm_area_struct *vma) +{ + __folio_large_mapcount_sanity_checks(folio, mapcount, vma->vm_mm->mm_id); + + VM_WARN_ON_ONCE(folio_mm_id(folio, 0) != MM_ID_DUMMY); + VM_WARN_ON_ONCE(folio_mm_id(folio, 1) != MM_ID_DUMMY); + + /* Note: mapcounts start at -1. */ + atomic_set(&folio->_large_mapcount, mapcount - 1); + folio->_mm_id_mapcount[0] = mapcount - 1; + folio_set_mm_id(folio, 0, vma->vm_mm->mm_id); +} + +static __always_inline void folio_add_large_mapcount(struct folio *folio, + int diff, struct vm_area_struct *vma) +{ + const mm_id_t mm_id = vma->vm_mm->mm_id; + int new_mapcount_val; + + folio_lock_large_mapcount(folio); + __folio_large_mapcount_sanity_checks(folio, diff, mm_id); + + new_mapcount_val = atomic_read(&folio->_large_mapcount) + diff; + atomic_set(&folio->_large_mapcount, new_mapcount_val); + + /* + * If a folio is mapped more than once into an MM on 32bit, we + * can in theory overflow the per-MM mapcount (although only for + * fairly large folios), turning it negative. In that case, just + * free up the slot and mark the folio "mapped shared", otherwise + * we might be in trouble when unmapping pages later. + */ + if (folio_mm_id(folio, 0) == mm_id) { + folio->_mm_id_mapcount[0] += diff; + if (!IS_ENABLED(CONFIG_64BIT) && unlikely(folio->_mm_id_mapcount[0] < 0)) { + folio->_mm_id_mapcount[0] = -1; + folio_set_mm_id(folio, 0, MM_ID_DUMMY); + folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT; + } + } else if (folio_mm_id(folio, 1) == mm_id) { + folio->_mm_id_mapcount[1] += diff; + if (!IS_ENABLED(CONFIG_64BIT) && unlikely(folio->_mm_id_mapcount[1] < 0)) { + folio->_mm_id_mapcount[1] = -1; + folio_set_mm_id(folio, 1, MM_ID_DUMMY); + folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT; + } + } else if (folio_mm_id(folio, 0) == MM_ID_DUMMY) { + folio_set_mm_id(folio, 0, mm_id); + folio->_mm_id_mapcount[0] = diff - 1; + /* We might have other mappings already. */ + if (new_mapcount_val != diff - 1) + folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT; + } else if (folio_mm_id(folio, 1) == MM_ID_DUMMY) { + folio_set_mm_id(folio, 1, mm_id); + folio->_mm_id_mapcount[1] = diff - 1; + /* Slot 0 certainly has mappings as well. */ + folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT; + } + folio_unlock_large_mapcount(folio); +} + +static __always_inline void folio_sub_large_mapcount(struct folio *folio, + int diff, struct vm_area_struct *vma) +{ + const mm_id_t mm_id = vma->vm_mm->mm_id; + int new_mapcount_val; + + folio_lock_large_mapcount(folio); + __folio_large_mapcount_sanity_checks(folio, diff, mm_id); + + new_mapcount_val = atomic_read(&folio->_large_mapcount) - diff; + atomic_set(&folio->_large_mapcount, new_mapcount_val); + + /* + * There are valid corner cases where we might underflow a per-MM + * mapcount (some mappings added when no slot was free, some mappings + * added once a slot was free), so we always set it to -1 once we go + * negative. + */ + if (folio_mm_id(folio, 0) == mm_id) { + folio->_mm_id_mapcount[0] -= diff; + if (folio->_mm_id_mapcount[0] >= 0) + goto out; + folio->_mm_id_mapcount[0] = -1; + folio_set_mm_id(folio, 0, MM_ID_DUMMY); + } else if (folio_mm_id(folio, 1) == mm_id) { + folio->_mm_id_mapcount[1] -= diff; + if (folio->_mm_id_mapcount[1] >= 0) + goto out; + folio->_mm_id_mapcount[1] = -1; + folio_set_mm_id(folio, 1, MM_ID_DUMMY); + } + + /* + * If one MM slot owns all mappings, the folio is mapped exclusively. + * Note that if the folio is now unmapped (new_mapcount_val == -1), both + * slots must be free (mapcount == -1), and we'll also mark it as + * exclusive. + */ + if (folio->_mm_id_mapcount[0] == new_mapcount_val || + folio->_mm_id_mapcount[1] == new_mapcount_val) + folio->_mm_ids &= ~FOLIO_MM_IDS_SHARED_BIT; +out: + folio_unlock_large_mapcount(folio); +} +#else /* !CONFIG_MM_ID */ +/* + * See __folio_rmap_sanity_checks(), we might map large folios even without + * CONFIG_TRANSPARENT_HUGEPAGE. We'll keep that working for now. + */ static inline void folio_set_large_mapcount(struct folio *folio, int mapcount, struct vm_area_struct *vma) { @@ -191,6 +355,7 @@ static inline void folio_sub_large_mapcount(struct folio *folio, { atomic_sub(diff, &folio->_large_mapcount); } +#endif /* CONFIG_MM_ID */ #define folio_inc_large_mapcount(folio, vma) \ folio_add_large_mapcount(folio, 1, vma) |